Bio


Our group applies mechanistic principles to develop new concepts in catalysis. A particular focus is the development of organometallic and organic catalysts for the synthesis of complex macromolecular architectures. In organometallic catalysis, we investigate catalysts that can access multiple kinetic states during a polymerization reaction in order to control sequence distribution. We have devised a novel strategy for the synthesis of elastomeric polypropylene utilizing a metallocene catalyst whose structure was designed to interconvert between chiral and achiral coordination geometries on the timescale of the synthesis of a single polymer chain. We have also developed a novel method for the synthesis of alternating copolymers of ethylene and propylene by exploiting catalysts that can access multiple coordination sites that exhibit different kinetic selectivities towards the two monomers. In collaboration with Jim Hedrick of IBM laboratories, we have developed an extensive platform of organic catalysts for the controlled ring-opening polymerization of lactones. Mechanistic studies of nucleophilic N-heterocyclic carbene catalysts revealed an unusual zwitterionic mechanism which enabled the synthesis of high molecular weight cyclic polyesters, a novel topology for these biodegradable and biocompatible macromolecules. These efforts combine elements of mechanistic organic and organometallic chemistry, polymer synthesis, and homogeneous catalysis to rationally design new macromolecular structures.

Academic Appointments


Honors & Awards


  • Postdoctoral Fellow, ETH Zurich (1988)
  • Young Investigator, NSF (1992)
  • A.P. Sloan Fellow, A.P. Sloan Foundation (1993)
  • Union Carbide Innovation Award, Union Carbide (1993)
  • Undergraduate Teaching Award, Phi Beta Kappa (1993)
  • Bing Teaching Award, Stanford University (1994)
  • Arthur C. Cope Scholar Award, Arthur C. Cope Foundation (1995)
  • Fresenius Award, Stanford University (1995)
  • Alan T. Waterman Award, National Science Foundation (1996)
  • Walter J. Gores Teaching Award, Stanford University (1997)
  • Wilhelm Manchot Professorship, Wilhelm Manchot Foundation (1997)
  • Alexander von Humbold Stiftung Award, Alexander von Humbold Foundation (2001)
  • Bass Fellow in Undergraduate Education, Stanford University (2005)
  • Cooperative Research Award in Polymer Science and Engineering, ACS (2009)
  • Presidential Green Chemistry Challenge Award, EPA (2012)

Professional Education


  • PhD, California Institute of Technology, Chemistry (1987)
  • BS, Washington and Lee University, Chemistry (1982)
  • BA, Washington and Lee University, Chemistry (1982)

2015-16 Courses


Stanford Advisees


All Publications


  • Electrooxidation of Alcohols with Electrode-Supported Transfer Hydrogenation Catalysts ACS CATALYSIS Buonaiuto, M., De Crisci, A. G., Jaramillo, T. F., Waymouth, R. M. 2015; 5 (12): 7343-7349
  • A Simple and Facile Approach to Aliphatic N-Substituted Functional Eight-Membered Cyclic Carbonates and Their Organocatalytic Polymerization JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Venkataraman, S., Ng, V. W., Coady, D. J., Horn, H. W., Jones, G. O., Fung, T. S., Sardon, H., Waymouth, R. M., Hedrick, J. L., Yang, Y. Y. 2015; 137 (43): 13851-13860
  • Catalytic Role of Multinuclear Palladium-Oxygen Intermediates in Aerobic Oxidation Followed by Hydrogen Peroxide Disproportionation JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Ingram, A. J., Walker, K. L., Zare, R. N., Waymouth, R. M. 2015; 137 (42): 13632-13646
  • Catalytic Dimerization of Crotonates ACS CATALYSIS Flanagan, J. C., Kang, E. J., Strong, N. I., Waymouth, R. M. 2015; 5 (9): 5328-5332
  • Cyclopropenimine Superbases: Competitive Initiation Processes in Lactide Polymerization ACS MACRO LETTERS Stukenbroeker, T. S., Bandar, J. S., Zhang, X., Lambert, T. H., Waymouth, R. M. 2015; 4 (8): 853-856
  • Structurally Dynamic Hydrogels Derived from 1,2-Dithiolanes JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Barcan, G. A., Zhang, X., Waymouth, R. M. 2015; 137 (17): 5650-5653

    Abstract

    The design and generation of adaptable materials derived from structurally dynamic polymers provides a strategy for generating smart materials that can respond to environmental stimuli or exhibit self-healing behavior. Herein we report an expedient organocatalytic ring-opening polymerization of cyclic carbonates containing pendant dithiolanes (trimethylene carbonate/dithiolane, TMCDT) from poly(ethylene oxide) diols to generate water-soluble triblock (ABA) copolymers containing a central poly(ethylene oxide) block and terminal dithiolane blocks. Hydrogels generated from the triblock copolymers and a cross-linking dithiol exhibited dynamic behavior as a result of the reversible ring opening of the pendant 1,2-dithiolanes. These materials exhibit self-healing behavior, can be injected through a syringe, and rapidly recover their mechanical properties after a severe strain deformation. The dynamic properties of these gels can be modulated with the number of dithiolane units, pH, and temperature.

    View details for DOI 10.1021/jacs.5b02161

    View details for Web of Science ID 000354338500004

  • N-Heterocyclic Carbene-Catalyzed Ring Opening Polymerization of e-Caprolactone with and without Alcohol Initiators: Insights from Theory and Experiment. journal of physical chemistry. B Jones, G. O., Chang, Y. A., Horn, H. W., Acharya, A. K., Rice, J. E., Hedrick, J. L., Waymouth, R. M. 2015; 119 (17): 5728-5737

    Abstract

    Computational investigations with density functional theory (DFT) have been performed on the N-heterocyclic carbene (NHC) catalyzed ring-opening polymerization of ε-caprolactone in the presence and in the absence of a methanol initiator. Much like the zwitterionic ring opening (ZROP) of δ-valerolactone which was previously reported, calculations predict that the mechanism of the ZROP of caprolactone that occurs without an alcohol present involves a high-barrier step involving ring opening of the zwitterionic tetrahedral intermediate formed after the initial nucleophilic attack of NHC on caprolactone. However, the operative mechanism by which caprolactone is polymerized in the presence of an alcohol initiator does not involve the analogous mechanism involving initial nucleophilic attack by the organocatalytic NHC. Instead, the NHC activates the alcohol through hydrogen bonding and promotes nucleophilic attack and the subsequent ring-opening steps that occur during polymerization. The largest free energy barrier for the hydrogen-bonding mechanism in alcohol involves nucleophilic attack, while that for both ZROP processes involves ring opening of the initially formed zwitterionic tetrahedral intermediate. The DFT calculations predict that the rate of polymerization in the presence of alcohol is faster than the reaction performed without an alcohol initiator; this prediction has been validated by experimental kinetic studies.

    View details for DOI 10.1021/acs.jpcb.5b01595

    View details for PubMedID 25848823

  • Organocatalytic Ring-Opening Polymerization of Trimethylene Carbonate To Yield a Biodegradable Polycarbonate JOURNAL OF CHEMICAL EDUCATION Chan, J. M., Zhang, X., Brennan, M. K., Sardon, H., Engler, A. C., Fox, C. H., Frank, C. W., Waymouth, R. M., Hedrick, J. L. 2015; 92 (4): 708-713

    View details for DOI 10.1021/ed500595k

    View details for Web of Science ID 000353368000023

  • Ion pairing effects in the zwitterionic ring opening polymerization of delta-valerolactone POLYMER CHEMISTRY Chang, Y. A., Waymouth, R. M. 2015; 6 (29): 5212-5218

    View details for DOI 10.1039/c5py00662g

    View details for Web of Science ID 000358024800005

  • Synthesis and Topological Trapping of Cyclic Poly(alkylene phosphates) MACROMOLECULES Stukenbroeker, T. S., Solis-Ibarra, D., Waymouth, R. M. 2014; 47 (23): 8224-8230

    View details for DOI 10.1021/ma501764c

    View details for Web of Science ID 000346325300012

  • Disassembly and reassembly of polyhydroxyalkanoates: Recycling through abiotic depolymerization and biotic repolymerization BIORESOURCE TECHNOLOGY Myung, J., Strong, N. I., Galega, W. M., Sundstrom, E. R., Flanagan, J. C., Woo, S., Waymouth, R. M., Criddle, C. S. 2014; 170: 167-174
  • Zwitterionic Ring Opening Polymerization with Isothioureas ACS MACRO LETTERS Zhang, X., Waymouth, R. M. 2014; 3 (10): 1024-1028

    View details for DOI 10.1021/mz500525n

    View details for Web of Science ID 000343673200014

  • Organocatalytic Ring-Opening Polymerization of Morpholinones: New Strategies to Functionalized Polyesters JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Blake, T. R., Waymouth, R. M. 2014; 136 (26): 9252-9255

    Abstract

    The oxidative lactonization of N-substituted diethanolamines with the Pd catalyst [LPd(OAc)]2(2+)[OTf(-)]2 generates N-substituted morpholin-2-ones. The organocatalytic ring-opening polymerization of N-acyl morpholin-2-ones occurs readily to generate functionalized poly(aminoesters) with N-acylated amines in the polyester backbone. The thermodynamics of the ring-opening polymerization depends sensitively on the hybridization of the nitrogen of the heterocyclic lactone. N-Acyl morpholin-2-ones polymerize readily to generate polymorpholinones, but the N-aryl or N-alkyl substituted morpholin-2-ones do not polymerize. Experimental and theoretical studies reveal that the thermodynamics of ring opening correlates to the degree of pyramidalization of the endocyclic N-atom. Deprotection of the poly(N-Boc-morpholin-2-one) yields a water-soluble, cationic polymorpholinone.

    View details for DOI 10.1021/ja503830c

    View details for Web of Science ID 000338692700005

    View details for PubMedID 24946200

  • Experimental and Computational Studies on the Mechanism of Zwitterionic Ring-Opening Polymerization of delta-Valerolactone with N-Heterocyclic Carbenes JOURNAL OF PHYSICAL CHEMISTRY B Acharya, A. K., Chang, Y. A., Jones, G. O., Rice, J. E., Hedrick, J. L., Horn, H. W., Waymouth, R. M. 2014; 118 (24): 6553-6560

    View details for DOI 10.1021/jp500200b

    View details for Web of Science ID 000337784100023

  • Zwitterionic Ring-Opening Polymerization: Models for Kinetics of Cyclic Poly(caprolactone) Synthesis MACROMOLECULES Brown, H. A., Xiong, S., Medvedev, G. A., Chang, Y. A., Abu-Omar, M. M., Caruthers, J. M., Waymouth, R. M. 2014; 47 (9): 2955-2963

    View details for DOI 10.1021/ma500395j

    View details for Web of Science ID 000336020900023

  • Trinuclear Pd3O2 Intermediate in Aerobic Oxidation Catalysis ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Ingram, A. J., Solis-Ibarra, D., Zare, R. N., Waymouth, R. M. 2014; 53 (22): 5648-5652

    Abstract

    The activation of O2 is a key step in selective catalytic aerobic oxidation reactions mediated by transition metals. The bridging trinuclear palladium species, [(LPd(II) )3 (μ(3) -O)2 ](2+) (L=2,9-dimethylphenanthroline), was identified during the [LPd(OAc)]2 (OTf)2 -catalyzed aerobic oxidation of 1,2-propanediol. Independent synthesis, structural characterization, and catalytic studies of the trinuclear compound show that it is a product of oxygen activation by reduced palladium species and is a competent intermediate in the catalytic aerobic oxidation of alcohols. The formation and catalytic activity of the trinuclear Pd3 O2 species illuminates a multinuclear pathway for aerobic oxidation reactions catalyzed by Pd complexes.

    View details for DOI 10.1002/anie.201400134

    View details for Web of Science ID 000337041600027

    View details for PubMedID 24711099

  • Titanium Bis(amidinates) Bearing Electron Donating Pendant Arms as Catalysts for Stereospecific Polymerization of Propylene ORGANOMETALLICS Elkin, T., Botoshansky, M., Waymouth, R. M., Eisen, M. S. 2014; 33 (4): 840-843

    View details for DOI 10.1021/om401165g

    View details for Web of Science ID 000331991800003

  • Zwitterionic Polymerization to Generate High Molecular Weight Cyclic Poly(Carbosiloxane)s JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Brown, H. A., Chang, Y. A., Waymouth, R. M. 2013; 135 (50): 18738-18741

    Abstract

    The zwitterionic ring-opening of 2,2,5,5-tetramethyl-2,5-disila-1-oxacyclopentane (TMOSC) with N-heterocyclic carbenes generates high molecular weight cyclic p(TMOSC). The NHC-mediated polymerization of TMOSC with 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes, 1) generates the poly(carbosiloxane) p(TMOSC) with molecular weights from 27,000 < Mn < 80,000 Da (1.4 < Mw/Mn < 2.2) within 30 min at room temp. With the more nucleophilic carbene 1,3,4,5-tetramethyl-imidazol-2-ylidene (4), the ring-opening polymerization occurs within minutes at room temperature to generate cyclic p(TMOSC) with molecular weights up to Mn = 940,000 Da (Mw/Mn = 3.2). The resulting p(TMOSC)s are predominantly cyclic as evidenced by dilute solution viscosity studies and MALDI-TOF MS. DFT calculations provide support for both zwitterionic and neutral, cyclic intermediates.

    View details for DOI 10.1021/ja409843v

    View details for Web of Science ID 000328865100009

    View details for PubMedID 24308512

  • Zwitterionic Ring-Opening Polymerization for the Synthesis of High Molecular Weight Cyclic Polymers ACCOUNTS OF CHEMICAL RESEARCH Brown, H. A., Waymouth, R. M. 2013; 46 (11): 2585-2596

    Abstract

    Cyclic polymers are an intriguing class of macromolecules. Because of the constraints of the cyclic topology and the absence of chain ends, the properties of these molecules differ from those of linear polymers in ways that remain poorly understood. Cyclic polymers present formidable synthetic challenges because the entropic penalty of coupling the chain ends grows exponentially with increasing molecular weight. In this Account, we describe recent progress in the application of zwitterionic ring-opening polymerization (ZROP) as a strategy for the synthesis of high molecular weight, cyclic polymers. Zwitterionic ring-opening polymerization involves the addition of neutral organic nucleophiles to strained heterocyclic monomers; under appropriate conditions, cyclization of the resultant macrozwitterions generates cyclic macromolecules. We discuss the mechanistic and kinetic features of these zwitterionic ring-opening reactions and the conditions that influence the efficiency of the initiation, propagation, and cyclization to generate high molecular weight cyclic polymers. N-Heterocyclic carbenes (NHC) are potent nucleophiles and relatively poor leaving groups, two features that are important for the generation of high molecular weight polymers. Investigations of the nature of the monomer and nucleophile have helped researchers understand the factors that govern the reactivity of these systems and their impact on the molecular weight and molecular weight distributions of the resulting cyclic polymers. We focus primarily on ZROP mediated by N-heterocyclic carbene nucleophiles but also discuss zwitterionic polymerizations with amidine, pyridine, and imidazole nucleophiles. The ZROP of N-carboxyanhydrides with N-hetereocyclic carbenes generates a family of functionalized cyclic polypeptoids. We can synthesize gradient lactone copolymers by exploiting differences in relative reactivity present in ZROP that differ from those of traditional metal-mediated polymerizations. These new synthetic methods have allowed us to investigate the influence of topology on the crystallization behavior, stereocomplexation, and solution properties of cyclic macromolecules.

    View details for DOI 10.1021/ar400072z

    View details for Web of Science ID 000327360800023

    View details for PubMedID 23789724

  • A Renewable Lignin-Lactide Copolymer and Application in Biobased Composites ACS SUSTAINABLE CHEMISTRY & ENGINEERING Chung, Y., Olsson, J. V., Li, R. J., Frank, C. W., Waymouth, R. M., Billington, S. L., Sattely, E. S. 2013; 1 (10): 1231-1238

    View details for DOI 10.1021/sc4000835

    View details for Web of Science ID 000325512000004

  • Electrooxidation of Alcohols Catalyzed by Amino Alcohol Ligated Ruthenium Complexes JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Brownell, K. R., McCrory, C. C., Chidsey, C. E., Perry, R. H., Zare, R. N., Waymouth, R. M. 2013; 135 (38): 14299-14305

    Abstract

    Ruthenium transfer hydrogenation catalysts physisorbed onto edge-plane graphite electrodes are active electrocatalysts for the oxidation of alcohols. Electrooxidation of CH3OH (1.23 M) in a buffered aqueous solution at pH 11.5 with [(η(6)-p-cymene)(η(2)-N,O-(1R,2S)-cis-1-amino-2-indanol)]Ru(II)Cl (2) on edge-plane graphite exhibits an onset current at 560 mV vs NHE. Koutecky-Levich analysis at 750 mV reveals a four-electron oxidation of methanol with a rate of 1.35 M(-1) s(-1). Mechanistic investigations by (1)H NMR, cyclic voltammetry, and desorption electrospray ionization mass spectrometry indicate that the electroxidation of methanol to generate formate is mediated by surface-supported Ru-oxo complexes.

    View details for DOI 10.1021/ja4055564

    View details for Web of Science ID 000330162900050

    View details for PubMedID 24044700

  • Chemoselective Pd-Catalyzed Oxidation of Polyols: Synthetic Scope and Mechanistic Studies JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Chung, K., Banik, S. M., De Crisci, A. G., Pearson, D. M., Blake, T. R., Olsson, J. V., Ingram, A. J., Zare, R. N., Waymouth, R. M. 2013; 135 (20): 7593-7602

    Abstract

    The regio- and chemoselective oxidation of unprotected vicinal polyols with [(neocuproine)Pd(OAc)]2(OTf)2 (1) (neocuproine = 2,9-dimethyl-1,10-phenanthroline) occurs readily under mild reaction conditions to generate α-hydroxy ketones. The oxidation of vicinal diols is both faster and more selective than the oxidation of primary and secondary alcohols; vicinal 1,2-diols are oxidized selectively to hydroxy ketones, whereas primary alcohols are oxidized in preference to secondary alcohols. Oxidative lactonization of 1,5-diols yields cyclic lactones. Catalyst loadings as low as 0.12 mol % in oxidation reactions on a 10 g scale can be used. The exquisite selectivity of this catalyst system is evident in the chemoselective and stereospecific oxidation of the polyol (S,S)-1,2,3,4-tetrahydroxybutane [(S,S)-threitol] to (S)-erythrulose. Mechanistic, kinetic, and theoretical studies revealed that the rate laws for the oxidation of primary and secondary alcohols differ from those of diols. Density functional theory calculations support the conclusion that β-hydride elimination to give hydroxy ketones is product-determining for the oxidation of vicinal diols, whereas for primary and secondary alcohols, pre-equilibria favoring primary alkoxides are product-determining. In situ desorption electrospray ionization mass spectrometry (DESI-MS) revealed several key intermediates in the proposed catalytic cycle.

    View details for DOI 10.1021/ja4008694

    View details for Web of Science ID 000319551000032

  • Octahedral Group IV Bis(phenolate) Catalysts for 1-Hexene Homopolymerization and Ethylene/1-Hexene Copolymerization MACROMOLECULES Kiesewetter, E. T., Waymouth, R. M. 2013; 46 (7): 2569-2575

    View details for DOI 10.1021/ma400116w

    View details for Web of Science ID 000317438300006

  • Chemoselective Oxidation of Polyols with Chiral Palladium Catalysts ORGANOMETALLICS De Crisci, A. G., Chung, K., Oliver, A. G., Solis-Ibarra, D., Waymouth, R. M. 2013; 32 (7): 2257-2266

    View details for DOI 10.1021/om4001549

    View details for Web of Science ID 000317370000028

  • Polymerizing Base Sensitive Cyclic Carbonates Using Acid Catalysis ACS MACRO LETTERS Coady, D. J., Horn, H. W., Jones, G. O., Sardon, H., Engler, A. C., Waymouth, R. M., Rice, J. E., Yang, Y. Y., Hedrick, J. L. 2013; 2 (4): 306-312

    View details for DOI 10.1021/mz3006523

    View details for Web of Science ID 000317813200006

  • Semicrystalline Dihydroxyacetone Copolymers Derived from Glycerol MACROMOLECULES Simon, J., Olsson, J. V., Kim, H., Tenney, I. F., Waymouth, R. M. 2012; 45 (23): 9275-9281

    View details for DOI 10.1021/ma302311h

    View details for Web of Science ID 000312122600006

  • Amidine-Mediated Zwitterionic Polymerization of Lactide ACS MACRO LETTERS Brown, H. A., De Crisci, A. G., Hedrick, J. L., Waymouth, R. M. 2012; 1 (9): 1113-1115

    View details for DOI 10.1021/mz300276u

    View details for Web of Science ID 000308855900005

  • Designed guanidinium-rich amphipathic oligocarbonate molecular transporters complex, deliver and release siRNA in cells PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Geihe, E. I., Cooley, C. B., Simon, J. R., Kiesewetter, M. K., Edward, J. A., Hickerson, R. P., Kaspar, R. L., Hedrick, J. L., Waymouth, R. M., Wender, P. A. 2012; 109 (33): 13171-13176

    Abstract

    The polyanionic nature of oligonucleotides and their enzymatic degradation present challenges for the use of siRNA in research and therapy; among the most notable of these is clinically relevant delivery into cells. To address this problem, we designed and synthesized the first members of a new class of guanidinium-rich amphipathic oligocarbonates that noncovalently complex, deliver, and release siRNA in cells, resulting in robust knockdown of target protein synthesis in vitro as determined using a dual-reporter system. The organocatalytic oligomerization used to synthesize these co-oligomers is step-economical and broadly tunable, affording an exceptionally quick strategy to explore chemical space for optimal siRNA delivery in varied applications. The speed and versatility of this approach and the biodegradability of the designed agents make this an attractive strategy for biological tool development, imaging, diagnostics, and therapeutic applications.

    View details for DOI 10.1073/pnas.1211361109

    View details for Web of Science ID 000307807000017

    View details for PubMedID 22847412

  • Organocatalytic Synthesis of Quinine-Functionalized Poly(carbonate)s BIOMACROMOLECULES Edward, J. A., Kiesewetter, M. K., Kim, H., Flanagan, J. C., Hedrick, J. L., Waymouth, R. M. 2012; 13 (8): 2483-2489

    Abstract

    The ring-opening polymerization of substituted cyclic carbonates with 1-(3,5-bis-trifluoromethyl-phenyl)-3-cyclohexyl-thiourea (TU)/1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) organocatalysts afford highly functionalized oligocarbonates. The fluorescent alkaloid quinine can be readily incorporated into the oligocarbonates either by initiation from quinine or by ring-opening polymerization of a quinine-functionalized cyclic carbonate (MTC-Q). Copolymerization of MTC-Q with a boc-protected guanidinium cyclic carbonate affords, after deprotection, highly water-soluble cationic copolymers functionalized with both quinine and pendant guanidinium groups. When multiple quinine groups are attached to the oligomers, they exhibit minimal fluorescence due to self-quenching. Upon hydrolysis, the fluorescence intensity increases, providing a potential strategy for monitoring the hydrolysis rates in real time.

    View details for DOI 10.1021/bm300718b

    View details for Web of Science ID 000307422300031

    View details for PubMedID 22849552

  • Facile Synthesis of Functionalized Lactones and Organocatalytic Ring-Opening Polymerization ACS MACRO LETTERS Kim, H., Olsson, J. V., Hedrick, J. L., Waymouth, R. M. 2012; 1 (7): 845-847

    View details for DOI 10.1021/mz3001397

    View details for Web of Science ID 000306503400013

  • Stereoselective and Regioselective Propylene Polymerization with Group 4 Bisphenolate Ether Complexes JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY Randoll, S., Kiesewetter, E. T., Waymouth, R. M. 2012; 50 (13): 2604-2611

    View details for DOI 10.1002/pola.26028

    View details for Web of Science ID 000304447800011

  • Transient Ru-methyl formate intermediates generated with bifunctional transfer hydrogenation catalysts PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Perry, R. H., Brownell, K. R., Chingin, K., Cahill, T. J., Waymouth, R. M., Zare, R. N. 2012; 109 (7): 2246-2250

    Abstract

    Desorption electrospray ionization (DESI) coupled to high-resolution Orbitrap mass spectrometry (MS) was used to study the reactivity of a (?-amino alcohol)(arene)RuCl transfer hydrogenation catalytic precursor in methanol (CH(3)OH). By placing [(p-cymene)RuCl(2)](2) on a surface and spraying a solution of ?-amino alcohol in methanol, two unique transient intermediates having lifetimes in the submillisecond to millisecond range were detected. These intermediates were identified as Ru (II) and Ru (IV) complexes incorporating methyl formate (HCOOCH(3)). The Ru (IV) intermediate is not observed when the DESI spray solution is sparged with Ar gas, indicating that O(2) dissolved in the solvent is necessary for oxidizing Ru (II) to Ru (IV). These proposed intermediates are supported by high-resolution and high mass accuracy measurements and by comparing experimental to calculated isotope profiles. Additionally, analyzing the bulk reaction mixture using gas chromatography-MS and nuclear magnetic resonance spectroscopy confirms the formation of HCOOCH(3). These results represent an example that species generated from the (?-amino alcohol)(arene)RuCl (II) catalytic precursor can selectively oxidize CH(3)OH to HCOOCH(3). This observation leads us to propose a pathway that can compete with the hydrogen transfer catalytic cycle. Although bifunctional hydrogen transfer with Ru catalysts has been well-studied, the ability of DESI to intercept intermediates formed in the first few milliseconds of a chemical reaction allowed identification of previously unrecognized intermediates and reaction pathways in this catalytic system.

    View details for DOI 10.1073/pnas.1118934109

    View details for Web of Science ID 000300489200024

    View details for PubMedID 22315417

  • Stereocomplexation in Cyclic and Linear Polylactide Blends MACROMOLECULES Shin, E. J., Jones, A. E., Waymouth, R. M. 2012; 45 (1): 595-598

    View details for DOI 10.1021/ma202184j

    View details for Web of Science ID 000298905000063

  • Palladium-Catalyzed Carbonylation of Diols to Cyclic Carbonates ADVANCED SYNTHESIS & CATALYSIS Pearson, D. M., Conley, N. R., Waymouth, R. M. 2011; 353 (16): 3007-3013
  • Polycondensation of Butenediol: Synthesis of Telechelic 2-Butene-1,4-diol Oligomers JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Kiesewetter, M. K., Edward, J. A., Kim, H., Waymouth, R. M. 2011; 133 (41): 16390-16393

    Abstract

    The catalytic condensation of cis-2-butene-1,4-diol with CpRu(MQA)(C(3)H(5)) (Cp = cyclopentadienyl, MQA = 4-methoxyquinoline-2-carboxylate) generates poly(2-butenediol), an unsaturated telechelic polyether diol with molecular weights between 400 and 4600 g/mol. This Ru(IV) allyl catalyst enchains 2-butene-1,4-diol primarily as the linear trans-2-butenyl ether (92%) along with vinyl branches (8%). These telechelic oligomers are useful chain extenders and macromonomers, as demonstrated by their use in the synthesis of poly(lactide)-b-poly(butenediol)-b-poly(lactide) triblock copolymers. Model studies support a proposed mechanism involving the formation of Ru(IV) allyl intermediates from allylic alcohols and chain growth by selective nucleophilic displacement at the terminus of the Ru(IV) allyl to generate trans-2-butenyl ether linkages.

    View details for DOI 10.1021/ja207465h

    View details for Web of Science ID 000295997500019

    View details for PubMedID 21939269

  • Synthesis and Structural Diversity of Mono-, Di- and Trinuclear Complexes with N,N '-Bis[(2-diphenylphosphanyl)phenyl]formamidine EUROPEAN JOURNAL OF INORGANIC CHEMISTRY Son, K., Pearson, D. M., Jeon, S., Waymouth, R. M. 2011: 4256-4261
  • Thermoresponsive nanostructured polycarbonate block copolymers as biodegradable therapeutic delivery carriers BIOMATERIALS Kim, S. H., Tan, J. P., Fukushima, K., Nederberg, F., Yang, Y. Y., Waymouth, R. M., Hedrick, J. L. 2011; 32 (23): 5505-5514

    Abstract

    Water-soluble, thermoresponsive block copolymers based on a biodegradable platform were synthesized by the ring opening polymerization of cyclic carbonate monomers functionalized with hydrophilic and hydrophobic groups for application as nanocarriers in medicine. The approach based on cyclic carbonate monomers derived from 2,2-bis(methylol)propionic acid (bis-MPA) allowed a simple and versatile route to functional monomers capable of undergoing ring opening polymerization (ROP). The resulting polymers possessed the predicted molecular weights based on the molar ratio between monomers to initiators and the narrow molecular weight distributions. Transmittance measurement for aqueous polymer solutions provided an evidence for temperature-responsiveness with lower critical solution temperature (LCST) in the range of 36 °C-60 °C, depending on the molecular weight of hydrophilic poly(ethylene glycol) (PEG) chains, compositions of copolymers, molar ratios of hydrophilic to hydrophobic monomers in the corona, and the hydrophobic core. This study showed synthetic advancement toward the design and preparation of biodegradable thermoresponsive polymers with extremely low CMC values for injectable drug delivery systems. TRC350-10,30,60, which possessed an LCST of 36 °C in PBS, was identified as a useful model polymer. Paclitaxel, an anti-cancer drug, was loaded into the micelles efficiently, giving rise to nano-sized particles with a narrow size distribution. Paclitaxel release from the micelles was faster, and cellular uptake of the micelles was higher at the body temperature (i.e. 37 °C) as compared to a temperature below the LCST. While the polymer was not cytotoxic, paclitaxel-loaded micelles killed HepG2 human liver carcinoma cells more efficiently at the body temperature as compared to free paclitaxel and paclitaxel-loaded micelles at the temperature below the LCST. These micelles are ideally suited to deliver anti-cancer drugs to tumor tissues through local injection.

    View details for DOI 10.1016/j.biomaterials.2011.04.017

    View details for Web of Science ID 000291900900020

    View details for PubMedID 21529935

  • Crystallization of Cyclic Polymers: Synthesis and Crystallization Behavior of High Molecular Weight Cyclic Poly(epsilon-caprolactone)s MACROMOLECULES Shin, E. J., Jeong, W., Brown, H. A., Koo, B. J., Hedrick, J. L., Waymouth, R. M. 2011; 44 (8): 2773-2779

    View details for DOI 10.1021/ma102970m

    View details for Web of Science ID 000289593200047

  • Oxidatively Resistant Ligands for Palladium-Catalyzed Aerobic Alcohol Oxidation ORGANOMETALLICS Pearson, D. M., Conley, N. R., Waymouth, R. M. 2011; 30 (6): 1445-1453

    View details for DOI 10.1021/om101037k

    View details for Web of Science ID 000288470900028

  • Stereospecific polymerization and selective oligomerization with coordination catalysts Waymouth, R. M., Kiesewetter, E. T., Son, K. AMER CHEMICAL SOC. 2011
  • Organocatalytic Depolymerization of Poly(ethylene terephthalate) JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY Fukushima, K., Coulembier, O., Lecuyer, J. M., Almegren, H. A., Alabdulrahman, A. M., Alsewailem, F. D., Mcneil, M. A., Dubois, P., Waymouth, R. M., Horn, H. W., Rice, J. E., Hedrick, J. L. 2011; 49 (5): 1273-1281

    View details for DOI 10.1002/pola.24551

    View details for Web of Science ID 000288465400027

  • Zwitterionic Copolymerization: Synthesis of Cyclic Gradient Copolymers ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Shin, E. J., Brown, H. A., Gonzalez, S., Jeong, W., Hedrick, J. L., Waymouth, R. M. 2011; 50 (28): 6388-6391

    View details for DOI 10.1002/anie.201101853

    View details for Web of Science ID 000292642600035

    View details for PubMedID 21618374

  • Kinetics of an Air- and Water-Stable Ruthenium(IV) Catalyst for the Deprotection of Allyl Alcohol in Water ORGANOMETALLICS Kiesewetter, M. K., Waymouth, R. M. 2010; 29 (22): 6051-6056

    View details for DOI 10.1021/om100892v

    View details for Web of Science ID 000284290600047

  • Chemoselectivity Diversity in the Reaction of LiNC6F5SiMe3 with Nitriles and the Synthesis, Structure, and Reactivity of Zirconium Mono- and Tris[2-(2-pyridyl)tetrafluorobenzimidazolate] Complexes INORGANIC CHEMISTRY Aharonovich, S., Botoshansky, M., Waymouth, R. M., Eisen, M. S. 2010; 49 (20): 9217-9229

    Abstract

    Unlike the reaction of LiNTMS(2)·TMEDA (TMS = SiMe(3); TMEDA = tetramethylethylenediamine) with 2-cyanopyridine, which results in the nearly exclusive formation of the amidinate, (Me(3)SiNC(6)F(5))Li·TMEDA (1) reacts with 2-cyanopyridine in toluene to yield quantitatively the lithium pyridyltetrafluorobenzimidazolate complex [C(6)F(4)N(2)C(2-C(5)H(4)N)]Li·TMEDA (3). In this work, the reactivity of complex 1 toward aromatic nitriles Ar-CN (Ar = Ph, o-OMeC(6)H(4), C(6)F(5), 2-pyridyl) was examined. Whereas complex 1 fails to react with o-methoxybenzonitrile, its reaction with benzonitrile or pentafluorobenzonitrile gives triphenyl-1,3,5-triazine (4) or the hexacoordinate lithium polymer [LiN(4-NCC(6)F(4))(C(6)F(5))·THF·TMEDA](n) (7), respectively. When 1 is reacted with 2-cyanopyridine in tetrahydrofuran (THF), the benzimidazolate coordination polymer {[C(6)F(4)N(2)C(2-C(5)H(4)N)]Li·THF}(n) (5) is obtained. Herein we discuss how this diverse chemoselectivity in the reaction of the examined lithium N-silylated amides LiNRTMS·TMEDA (R = TMS, C(6)F(5)) with nitriles is influenced by the electronic properties of the nitrile or amide substituents and by the ability of these substituents to interact with the lithium or silicon atoms. Further, we present the syntheses and structures of zirconium tris(pyridyltetrafluorobenzimidazolate) chloride (10) and zirconium bis(dimethylamido)(pyridyltetrafluorobenzimidazolate) chloride·THF (11) complexes. These complexes, the first prepared zirconium mono- and tris(benzimidazolate)s, were crystallographically characterized and examined in the polymerization of propylene with methyl aluminoxane (1:1000 Zr/Al molar ratio).

    View details for DOI 10.1021/ic100696r

    View details for Web of Science ID 000282783400020

    View details for PubMedID 20857913

  • Selective Ethylene Oligomerization in the Presence of ZnR2: Synthesis of Terminally-Functionalized Ethylene Oligomers ORGANOMETALLICS Son, K., Waymouth, R. M. 2010; 29 (16): 3515-3520

    View details for DOI 10.1021/om100503v

    View details for Web of Science ID 000280794400008

  • The Depolymerization of Poly(ethylene terephthalate) (PET) Using N-Heterocyclic Carbenes from Ionic Liquids JOURNAL OF CHEMICAL EDUCATION Kamber, N. E., Tsujii, Y., Keets, K., Waymouth, R. M., Pratt, R. C., Nyce, G. W., Hedrick, J. L. 2010; 87 (5): 519-521

    View details for DOI 10.1021/ed800152c

    View details for Web of Science ID 000276639900021

  • Stereospecific Octahedral Group 4 Bis(phenolate) Ether Complexes for Olefin Polymerization JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Kiesewetter, E. T., Randoll, S., Radlauer, M., Waymouth, R. M. 2010; 132 (16): 5566-?

    Abstract

    Octahedral group 4 bisphenolate ether complexes, activated by methylaluminoxane, are highly active and stereospecific alpha-olefin polymerization catalysts. X-ray crystallographic analysis reveals the Zr and Hf complexes to be closely isostructural; the bond lengths of the Hf complex are slightly shorter, but the maximum deviation is only 0.062 A. Despite the structural similarity of the Hf and Zr complexes, the Hf complexes generate more highly stereoselective catalysts. In addition to the influence of the transition metal, the structure of the ligand has a large influence on the stereospecificity. Bis-tert-butyl phenyl substituted complexes of Hf and Zr, when activated by MAO at 50-80 degrees C, generate high molecular weight polypropylene (M(n) = 130,000-360,000 g/mol) with isotacticities [mmmm] > 97% and melting points as high as 165 degrees C.

    View details for DOI 10.1021/ja100627x

    View details for Web of Science ID 000276991700016

    View details for PubMedID 20359183

  • Stereospecific Styrene Polymerization and Ethylene-Styrene Copolymerization with Titanocenes Containing a Pendant Amine Donor JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY Son, K., Waymouth, R. M. 2010; 48 (7): 1579-1585

    View details for DOI 10.1002/pola.23912

    View details for Web of Science ID 000275848000013

  • Organocatalysis: Opportunities and Challenges for Polymer Synthesis MACROMOLECULES Kiesewetter, M. K., Shin, E. J., Hedrick, J. L., Waymouth, R. M. 2010; 43 (5): 2093-2107

    View details for DOI 10.1021/ma9025948

    View details for Web of Science ID 000274928400001

  • Acyclic Guanidines as Organic Catalysts for Living Polymerization of Lactide MACROMOLECULES Zhang, L., Pratt, R. C., Nederberg, F., Horn, H. W., Rice, J. E., Waymouth, R. M., Wade, C. G., Hedrick, J. L. 2010; 43 (3): 1660-1664

    View details for DOI 10.1021/ma901776x

    View details for Web of Science ID 000274268400067

  • Lithium Furyl and Pyridyl Amidinates as Building Blocks in Coordination Polymers, Ladder and Cage Structures INORGANIC CHEMISTRY Aharonovich, S., Botoshanski, M., Rabinovich, Z., Waymouth, R. M., Eisen, M. S. 2010; 49 (3): 1220-1229

    Abstract

    Lithium N,N'-bis(trimethylsilyl)heterocyclic amidinate complexes with 3- and 4-pyridyl and 3-furyl carbon substituents were prepared by addition of the corresponding nitriles to LiN(SiMe(3))(2) (LiNTMS(2)) solution. In the presence of N,N,N',N' tetramethylethylene diamine (TMEDA), both pyridyl amidinates crystallize as coordination polymers with an amidinate-Li-pyridyl backbone. The 4-pyridyl derivative (7) creates a linear polymer with amidinate-Li-TMEDA units as side chains, whereas the 3-pyridyl polymer (6) has a two-dimensional (2D) network structure in which TMEDA serves as a cross-linker. Solvation of the reaction mixture of 3-furonitrile and LiNTMS(2) with TMEDA affords the monomeric 3-furyl amidinate Li TMEDA complex (3). Crystals of the Li(2)O complex {[3-furyl-C-(NTMS)(2)Li](4).Li(2)O}.C(7)H(8) (4) are obtained from toluene by partial hydrolysis of the unsolvated 3-furyl amidinate (2). Degradation of the polymer (7) to monomeric units can be achieved by solvation in toluene or by reaction with TMS(2)NLi.TMEDA that affords crystals of the complex {NTMS(2)Li.[4-C(5)H(4)N-C(NTMS)(2)Li.TMEDA]}(2).(NTMS(2)Li.TMEDA) (8). The formation of these aggregates can be rationalized by directed substitution of TMEDA with pyridyl moieties and by the laddering principle.

    View details for DOI 10.1021/ic902183c

    View details for Web of Science ID 000273785500054

    View details for PubMedID 20039691

  • Mono- and bis-amidinate 2,6-xylylimido vanadium chlorides: synthesis, structure, and reactivity DALTON TRANSACTIONS Aharonovich, S., Botoshansky, M., Tumanskii, B., Nomura, K., Waymouth, R. M., Eisen, M. S. 2010; 39 (24): 5643-5649

    Abstract

    Salt metathesis of (2,6-xylylimido) vanadium trichloride (1) with the unsolvated or the TMEDA lithium p-Et benzamidinate complexes (2 and 3, respectively, in 1 : 2 V : Li molar ratio) yields bis[N,N'-bis(trimethylsilyl) p-Et benzamidinate](2,6-xylylimido)VCl (4) as dark brown, diamond-shaped crystals. When equimolar amounts of complexes 1 and 2 are reacted, a mixture of the bis (4) and mono (5) imidovanadium amidinates results. A similar mixture is also obtained by a ligand metathesis reaction of the bis amidinate complex 4 and complex 1. When the synthesis of the mono amidinate 5 is attempted with the TMEDA lithium amidinate complexes 3 or the 3-pyridyl derivative (7) (in 1 : 1 V : Li molar ratio) a redox reaction takes place to produce (kappa(2)-TMEDA)(2,6-xylylimido)V(IV)Cl(2) (6) as crystalline, mustard-yellow plates. The activity of complex 4 in ethylene polymerization was negligible with MAO or MAO\(CPh(3))(+)[B(C(6)F(5))(4)](-) as co-catalysts.

    View details for DOI 10.1039/b925974k

    View details for Web of Science ID 000278588000011

    View details for PubMedID 20480084

  • Selective Catalytic Oxidation of Glycerol to Dihydroxyacetone ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Painter, R. M., Pearson, D. M., Waymouth, R. M. 2010; 49 (49): 9456-9459

    View details for DOI 10.1002/anie.201004063

    View details for Web of Science ID 000285210300028

    View details for PubMedID 21031380

  • Cyclic Guanidine Organic Catalysts: What Is Magic About Triazabicyclodecene? JOURNAL OF ORGANIC CHEMISTRY Kiesewetter, M. K., Scholten, M. D., Kirn, N., Weber, R. L., Hedrick, J. L., Waymouth, R. M. 2009; 74 (24): 9490-9496

    Abstract

    The bicyclic guanidine 1,5,7- triazabicyclo[4.4.0]dec-5-ene (TBD) is an effective organocatalyst for the formation of amides from esters and primary amines. Mechanistic and kinetic investigations support a nucleophilic mechanism where TBD reacts reversibly with esters to generate an acyl-TBD intermediate that acylates amines to generate the amides. Comparative investigations of the analogous bicyclic guanidine 1,4,6-triazabicyclo[3.3.0]oct-4-ene (TBO) reveal it to be a much less active acylation catalyst than TBD. Theoretical and mechanistic studies imply that the higher reactivity of TBD is a consequence of both its higher basicity and nucleophilicity than TBO as well as the high reactivity of the acyl-TBD intermediate, which is sterically prevented from adopting a planar amide structure.

    View details for DOI 10.1021/jo902369g

    View details for Web of Science ID 000272462100033

    View details for PubMedID 19928812

  • Oligocarbonate Molecular Transporters: Oligomerization-Based Syntheses and Cell-Penetrating Studies JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Cooley, C. B., Trantow, B. M., Nederberg, F., Kiesewetter, M. K., Hedrick, J. L., Waymouth, R. M., Wender, P. A. 2009; 131 (45): 16401-?

    Abstract

    A new family of guanidinium-rich molecular transporters featuring a novel oligocarbonate backbone with 1,7-side chain spacing is described. Conjugates can be rapidly assembled irrespective of length in a one-step oligomerization strategy that can proceed with concomitant introduction of probes (or by analogy drugs). The new transporters exhibit excellent cellular entry as determined by flow cytometry and fluorescence microscopy, and the functionality of their drug delivery capabilities was confirmed by the delivery of the bioluminescent small molecule probe luciferin and turnover by its intracellular target enzyme.

    View details for DOI 10.1021/ja907363k

    View details for Web of Science ID 000271723000030

    View details for PubMedID 19860416

  • Mechanistic Studies of the Oxidative Dehydrogenation of Methanol Using a Cationic Palladium Complex ORGANOMETALLICS Pearson, D. M., Waymouth, R. M. 2009; 28 (13): 3896-3900

    View details for DOI 10.1021/om900217s

    View details for Web of Science ID 000267694100047

  • Hierarchical Supermolecular Structures for Sustained Drug Release SMALL Tan, J. P., Kim, S. H., Nederberg, F., Appel, E. A., Waymouth, R. M., Zhang, Y., Hedrick, J. L., Yang, Y. Y. 2009; 5 (13): 1504-1507

    View details for DOI 10.1002/smll.200801756

    View details for Web of Science ID 000267903200003

    View details for PubMedID 19326354

  • Simple Approach to Stabilized Micelles Employing Miktoarm Terpolymers and Stereocomplexes with Application in Paclitaxel Delivery BIOMACROMOLECULES Nederberg, F., Appel, E., Tan, J. P., Kim, S. H., Fukushima, K., Sly, J., Miller, R. D., Waymouth, R. M., Yang, Y. Y., Hedrick, J. L. 2009; 10 (6): 1460-1468

    Abstract

    A simple and versatile approach to miktoarm co- and terpolymers from carbonate functional oligomers is described. The key building block employed is a carboxylic acid functional cyclic carbonate, derived from 2,2-bis(methylol)propionic acid, that was readily coupled to a hydroxyl functional monomethylether poly(ethylene glycol) oligomer. Ring-opening of the cyclic carbonate using functional amines generates a carbamate linkage bearing a functional group capable of initiating either controlled radical or ring-opening polymerization, together with a primary hydroxyl group for ring-opening polymerization. Two tandem polymerization steps were possible which add the second two arms, thus generating the targeted ABC miktoarm terpolymer. The resulting amphiphilic miktoarm terpolymers containing poly(D- and L-lactide) formed polylactide stereocomplexes in the bulk. In aqueous solution, the stereocomplex mixture of Y-shaped miktoarm copolymers, poly(ethylene glycol)-poly(D-lactide)-poly(D-lactide) and poly(ethylene glycol)-poly(L-lactide)-poly(L-lactide), or the stereoblock miktoarm poly(ethylene glycol)-poly(D-lactide)-poly(L-lactide) form stabilized micelles with a significantly lower critical micelle concentration than those derived from conventional stereo regular linear or Y-shaped amphiphiles. This simple and versatile approach provides a useful synthetic route to complex macromolecular architectures that can assemble into stable micelles. These micelles provide high capacity for loading of the anticancer drug paclitaxel and possess narrow size distribution as well as unique structure, leading to sustained and near zero-ordered release of drug without significant initial burst.

    View details for DOI 10.1021/bm900056g

    View details for Web of Science ID 000266860700018

    View details for PubMedID 19385659

  • Zwitterionic Polymerization: A Kinetic Strategy for the Controlled Synthesis of Cyclic Polylactide JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Jeong, W., Shin, E. J., Culkin, D. A., Hedrick, J. L., Waymouth, R. M. 2009; 131 (13): 4884-4891

    Abstract

    The zwitterionic ring-opening polymerization of lactide initiated by N-heterocyclic carbenes generates cyclic polylactides with well-defined molecular weights between M(n) = 5000 and 30,000 g/mol with narrow polydispersities (M(w)/M(n) < or = 1.31). These zwitterionic polymerizations are extremely rapid (k(p) = 48.7 M(-1) s(-1)), but also exhibit exceptional control of molecular weight and molecular weight distribution. The unusual kinetic features of these zwitterionic polymerizations are illuminated with kinetic and mechanistic investigations, which implicate a mechanism that involves a slow initiation step (second order in [M]), a propagation step (first order in [M]) that is much faster than initiation (k(i) = 0.274 M(-2) s(-1)), cyclization (k(c) = 0.0575 s(-1)), and depropagation (k(d) = 0.208 s(-1)). Numerical and stochastic simulations of the kinetic data provide a kinetic rationale for the evolution of molecular weight with monomer conversion: the molecular weights increase with increasing monomer conversion, exhibit a nonzero intercept near 0% monomer conversion, and are relatively insensitive to the initial monomer-to-initiator ratio. The observed narrow molecular weight distributions are due to a high rate of propagation relative to cyclization and chain transfer. Kinetic simulations define the kinetic criteria under which the active zwitterions remain in solution; these simulations were substantiated by chain-extension experiments, which provide experimental evidence for chain extension of the zwitterions and reinitiation by the N-heterocyclic carbenes liberated upon macrocyclization. The kinetic model rationalizes some of the unique features of zwitterionic ring-opening polymerization and provides a useful mechanistic framework to optimize these polymerizations as a strategy to generate well-defined cyclic polyesters.

    View details for DOI 10.1021/ja809617v

    View details for Web of Science ID 000264806300064

    View details for PubMedID 19334780

  • N-Heterocyclic Carbenes for the Organocatalytic Ring-Opening Polymerization of epsilon-Caprolactone MACROMOLECULES Kamber, N. E., Jeong, W., Gonzalez, S., Hedrick, J. L., Waymouth, R. M. 2009; 42 (5): 1634-1639

    View details for DOI 10.1021/ma802618h

    View details for Web of Science ID 000263883000035

  • Mixed Micelle Formation through Stereocomplexation between Enantiomeric Poly(lactide) Block Copolymers MACROMOLECULES Kim, S. H., Tan, J. P., Nederberg, F., Fukushima, K., Yang, Y. Y., Waymouth, R. M., Hedrick, J. L. 2009; 42 (1): 25-29

    View details for DOI 10.1021/ma801739x

    View details for Web of Science ID 000262263200006

  • Copolymerization of Styrene and Ethylene at High Temperature with Titanocenes Containing a Pendant Amine Donor MACROMOLECULES Son, K., Joege, F., Waymouth, R. M. 2008; 41 (24): 9663-9668

    View details for DOI 10.1021/ma801853f

    View details for Web of Science ID 000261767400024

  • Application of Block-Copolymer Supramolecular Assembly for the Fabrication of Complex TiO2 Nanostructures SMALL Kim, S. H., Park, O., Nederberg, F., Topuria, T., Krupp, L. E., Kim, H., Waymouth, R. M., Hedrick, J. L. 2008; 4 (12): 2162-2165

    View details for DOI 10.1002/smll.200801115

    View details for Web of Science ID 000261905100015

    View details for PubMedID 18975297

  • Organocatalytic Approach to Amphiphilic Comb-Block Copolymers Capable of Stereocomplexation and Self-Assembly BIOMACROMOLECULES Fukushima, K., Pratt, R. C., Nederberg, F., Tan, J. P., Yang, Y. Y., Waymouth, R. M., Hedrick, J. L. 2008; 9 (11): 3051-3056

    Abstract

    Biocompatible amphiphilic block copolymers comprised of poly(ethylene glycol) (PEG) as the hydrophilic component and a poly(methylcarboxytrimethylene carbonate) (PMTC) as a hydrophobic backbone having either poly(L-lactide) (L-PLA) or poly(D-lactide) (D-PLA) branches were prepared by organocatalytic ring-opening polymerization (ROP). The polycarbonate backbone was prepared by copolymerization of two different MTC-type monomers (MTCs) including a tetrahydropyranyloxy protected hydroxyl group, a masked initiator for a subsequent ROP step. Interestingly, the organic catalyst used in the ROP of MTCs was also effective for acetylation of the hydroxyl end-groups by the addition of acetic anhydride added after polymerization. Acidic deprotection of the tetrahydropyranyloxy (THP) protecting group on the carbonate chain generated hydroxyl functional groups that served as initiators for the ROP of either D- or L-lactide. Comb-shaped block copolymers of predictable molecular weights and narrow polydispersities (approximately 1.3) were prepared with up to 8-PLA branches. Mixtures of the D- and L-lactide based copolymers were studied to understand the effect of noncovalent interactions or stereocomplexation on the properties.

    View details for DOI 10.1021/bm800526k

    View details for Web of Science ID 000260856900012

    View details for PubMedID 18844407

  • Group Transfer Polymerization of Acrylates Catalyzed by N-Heterocyclic Carbenes MACROMOLECULES Scholten, M. D., Hedrick, J. L., Waymouth, R. M. 2008; 41 (20): 7399-7404

    View details for DOI 10.1021/ma801281q

    View details for Web of Science ID 000260255800023

  • Copolymerization behavior of titanium imidazolin-2-iminato complexes JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY Stelzig, S. H., Tamm, M., Waymouth, R. M. 2008; 46 (18): 6064-6070

    View details for DOI 10.1002/pola.22918

    View details for Web of Science ID 000259325100010

  • Structure-reactivity relationships of amido-pyridine-supported rare-earth-metal alkyl complexes ORGANOMETALLICS Zimmermann, M., Tornroos, K. W., Waymouth, R. M., Anwander, R. 2008; 27 (17): 4310-4317

    View details for DOI 10.1021/om701195x

    View details for Web of Science ID 000258898300008

  • The reaction mechanism for the organocatalytic ring-opening polymerization of L-lactide using a guanidine-based catalyst: Hydrogen-bonded or covalently bound? JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Chuma, A., Horn, H. W., Swope, W. C., Pratt, R. C., Zhang, L., Lohmeijer, B. G., Wade, C. G., Waymouth, R. M., Hedrick, J. L., Rice, J. E. 2008; 130 (21): 6749-6754

    Abstract

    We have investigated two alternative mechanisms for the ring-opening polymerization of l-lactide using a guanidine-based catalyst, the first involving acetyl transfer to the catalyst, and the second involving only hydrogen bonding to the catalyst. Using computational chemistry methods, we show that the hydrogen bonding pathway is considerably preferred over the acetyl transfer pathway and that this is consistent with experimental information.

    View details for DOI 10.1021/ja0764411

    View details for Web of Science ID 000256158200042

    View details for PubMedID 18454532

  • POLY 125-Stereocomplex interactions in cyclic and linear polylactides Jones, A. E., Shin, E. J., Waymouth, R. M. AMER CHEMICAL SOC. 2008
  • POLY 277-Organocatalytic ring-opening polymerization approach to fully degradable amphiphilic copolymers Fukushima, K., Pratt, R. C., Nederberg, F., Waymouth, R. M., Hedrick, J. L. AMER CHEMICAL SOC. 2008
  • POLY 129-Living ring-opening polymerization of cyclic esters with phosphazene organocatalysts Kester, B. S., Logan, J. W., Nederberg, F., Pratt, R. C., Wade, C. G., Waymouth, R. M., Hedrick, J. L. AMER CHEMICAL SOC. 2008
  • New bimetallic complexes of late transition metals involving pyrazole-bridged bis N-heterocyclic carbene ligands DALTON TRANSACTIONS Jeon, S., Waymouth, R. M. 2008: 437-439

    Abstract

    Bimetallic Ni, Rh, and Ir complexes of pyrazolate biscarbene containing bulky substituents have been synthesized and characterized by X-ray crystallography; the Ni complex dimerizes to a highly congested L(2)Ni(2) structure, whereas the corresponding Rh and Ir complexes form bimetallic LM(2) structures.

    View details for DOI 10.1039/b715212d

    View details for Web of Science ID 000252254300003

    View details for PubMedID 18185857

  • Tagging alcohols with cyclic carbonate: a versatile equivalent of (meth)acrylate for ring-opening polymerization CHEMICAL COMMUNICATIONS Pratt, R. C., Nederberg, F., Waymouth, R. M., Hedrick, J. L. 2008: 114-116

    Abstract

    Cyclic carbonate monomers based on a single biocompatible scaffold allow for incorporation of a wide range of functional groups into macromolecules via ring-opening polymerization.

    View details for DOI 10.1039/b713925j

    View details for Web of Science ID 000251633000026

    View details for PubMedID 18399418

  • Hierarchical assembly of nanostructured organosilicate networks via stereocomplexation of block copolymers NANO LETTERS Kim, S. H., Nederberg, F., Zhang, L., Wade, C. G., Waymouth, R. M., Hedrick, J. L. 2008; 8 (1): 294-301

    Abstract

    The effect of the stereochemistry of polylactide (PLA)-based block copolymers on templated inorganic nanostructures has been investigated from the self-assembly of a stereoisomer pair/organosilicate mixture followed by organosilicate vitrification and copolymer thermolysis. Isomeric PLA homopolymers, block copolymers, and a stereoblock copolymer were prepared by ring-opening polymerization of D-, L-, or rac-lactide using an organocatalytic catalyst. Both differential scanning calorimetry and atomic force microscopy showed the formation of a stereocomplex between enantiomeric stereoisomers, that is, block copolymer/block copolymer and block copolymer/homopolymer mixtures as well as a stereoblock copolymer. The unique noncovalent interactions driven by stereocomplexation of D- and L-lactide provided supramolecular structures with a hierarchical order as characterized by distinctive vertical and horizontal growth of toroidal nanostructured inorganic features. This study demonstrates the potential of hierarchically assembling suprastructures that bridge the nano- to mesoscale feature sizes in the design of tunable functional nanomaterials suitable for future applications of microelectronics, material science, and bioengineering.

    View details for DOI 10.1021/nl0726813

    View details for Web of Science ID 000252257700052

    View details for PubMedID 18095737

  • Organocatalytic ring-opening polymerization CHEMICAL REVIEWS Kamber, N. E., Jeong, W., Waymouth, R. M., Pratt, R. C., Lohmeijer, B. G., Hedrick, J. L. 2007; 107 (12): 5813-5840

    View details for DOI 10.1021/cr068415b

    View details for Web of Science ID 000251583300012

    View details for PubMedID 17988157

  • Synthesis of biomimetic poly(hydroxybutyrate): Alkoxy- and carboxytriazolines as latent ionic initiator MACROMOLECULES Coulembier, O., Delva, X., Hedrick, J. L., Waymouth, R. M., Dubois, P. 2007; 40 (24): 8560-8567

    View details for DOI 10.1021/ma071575k

    View details for Web of Science ID 000251094500013

  • Aerobic alcohol oxidation with cationic palladium complexes: insights into catalyst design and decomposition ORGANOMETALLICS Conley, N. R., Labios, L. A., Pearson, D. M., McCrory, C. C., Waymouth, R. M. 2007; 26 (23): 5447-5453

    View details for DOI 10.1021/om700492n

    View details for Web of Science ID 000250556900001

  • New ground for organic catalysis: A ring-opening polymerization approach to hydrogels BIOMACROMOLECULES Nederberg, F., Trang, V., Pratt, R. C., Mason, A. F., Frank, C. W., Waymouth, R. M., Hedrick, J. L. 2007; 8 (11): 3294-3297

    Abstract

    Herein, we describe an organocatalytic living polymerization approach to network and subsequent hydrogel formation. Cyclic carbonate-functionalized macromolecules were ring-opened using an alcoholic initiator in the presence of an organic catalyst, amidine 1,8-diazabicyclo[5.4.0]undec-7-ene. A model reaction for the cross-linking identified monomer concentration-dependent reaction regimes, and enhanced kinetic control was demonstrated by introducing a co-monomer, trimethylene carbonate. The addition of the co-monomer facilitated near-quantitative conversion of monomer to polymer (>96%). Resulting poly(ethylene glycol) networks swell significantly in water, and an open co-continuous (water-gel) porous structure was observed by scanning electron microscopy. The organocatalytic ring-opening polymerization of cyclic carbonate functional macromonomers using alcoholic initiators provides a simple, efficient, and versatile approach to hydrogel networks.

    View details for DOI 10.1021/bm700895d

    View details for Web of Science ID 000250960300002

    View details for PubMedID 17994785

  • N-Alkoxyimidazolylidene transition-metal complexes: Application to [5+2] and [4+2] cycloaddition reactions ORGANOMETALLICS Gomez, F. J., Kamber, N. E., Deschamps, N. M., Cole, A. P., Wender, P. A., Waymouth, R. M. 2007; 26 (18): 4541-4545

    View details for DOI 10.1021/om700493y

    View details for Web of Science ID 000248865600026

  • POLY 556-Group transfer polymerization of acrylates and methacrylates using N-heterocyclic carbene catalysts Scholten, M. D., Hedrick, J. L., Waymouth, R. M. AMER CHEMICAL SOC. 2007
  • POLY 260-Polyesters from renewable resources: Organocatalytic strategies for controlled polymerization reactions Waymouth, R. M., Hedrick, J. L., Pratt, R. C., Nederberg, F., Lohmeijer, B. G., Culkin, D. A., Coulembier, O., Kamber, N. E., Jeong, W., Kiesewetter, M. K., Shin, E. J. AMER CHEMICAL SOC. 2007
  • POLY 538-An organocatalytic route to functional and biodegradable hydrogels Nederberg, F., Pratt, R. C., Mason, A. F., Waymouth, R. M., Hedrick, J. L. AMER CHEMICAL SOC. 2007
  • N-Heterocyclic carbene-mediated zwitterionic polymerization: An expedient organocatalytic route to cyclic polyesters Jeong, W., Shin, E. J., Culkin, D. A., Hedrick, J. L., Waymouth, R. M. AMER CHEMICAL SOC. 2007
  • POLY 484-Phosphazene bases for the organocatalytic living ring-opening polymerization of cyclic esters Zhang, L., Nederberg, F., Pratt, R., Waymouth, R., Hedrick, J. L., Wade, C. G. AMER CHEMICAL SOC. 2007
  • POLY 508-Functionalizing polyesters and polycarbonates: Covalent tagging of alcohols for ring-opening polymerization Pratt, R. C., Nederberg, F., Waymouth, R. M., Hedrick, J. L. AMER CHEMICAL SOC. 2007
  • Synthesis and reactivity of allyl nickel(II) N-heterocyclic carbene enolate complexes JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY Benson, S., Payne, B., Waymouth, R. M. 2007; 45 (16): 3637-3647

    View details for DOI 10.1002/pola.22113

    View details for Web of Science ID 000248354900016

  • Organic spirocyclic initiators for the ring-expansion polymerization of beta-lactones JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Jeong, W., Hedrick, J. L., Waymouth, R. M. 2007; 129 (27): 8414-?

    View details for DOI 10.1021/ja072037q

    View details for Web of Science ID 000247759400008

    View details for PubMedID 17579414

  • Phosphazene bases: A new category of organocatalysts for the living ring-opening polymerization of cyclic esters MACROMOLECULES Zhang, L., Nederberg, F., Pratt, R. C., Waymouth, R. M., Hedrick, J. L., Wade, C. G. 2007; 40 (12): 4154-4158

    View details for DOI 10.1021/ma070316s

    View details for Web of Science ID 000247138500013

  • Zwitterionic polymerization of lactide to cyclic poly(lactide) by using N-heterocyclic carbene organocatalysts ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Culkin, D. A., Jeong, W., Csihony, S., Gomez, E. D., Balsara, N. R., Hedrick, J. L., Waymouth, R. M. 2007; 46 (15): 2627-2630

    View details for DOI 10.1002/anie.200604740

    View details for Web of Science ID 000245614600017

    View details for PubMedID 17330912

  • Organocatalytic ring opening polymerization of trimethylene carbonate BIOMACROMOLECULES Nederberg, F., Lohmeijer, B. G., Leibfarth, F., Pratt, R. C., Choi, J., Dove, A. P., Waymouth, R. M., Hedrick, J. L. 2007; 8 (1): 153-160

    Abstract

    A variety of organocatalysts has been surveyed in the ring opening polymerization of trimethylene carbonate. Excellent control was found for several of these catalysts yielding well-defined polycarbonates with molecular weights up to 50,000 g mol(-1), polydispersities below 1.08, and high end-group fidelity. Melt or bulk polymerization was accomplished without loss of control of molecular weight or polydispersity, and random ester-carbonate bulk polymerizations were also demonstrated. Furthermore, by combining disparate polymerization techniques using bifunctional initiators, the mild polymerization conditions allow for the preparation of new block copolymers. Hydrogen-bond activation of monomer and initiator/propagating species is proposed as the underlying mechanism, which can be tuned to mitigate adverse side reactions.

    View details for DOI 10.1021/bm060795n

    View details for Web of Science ID 000243337600021

    View details for PubMedID 17206801

  • A distinctive organocatalytic approach to complex macromolecular architectures ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Coulembier, O., Kiesewetter, M. K., Mason, A., Dubois, P., Hedrick, J. L., Waymouth, R. M. 2007; 46 (25): 4719-4721

    View details for DOI 10.1002/anie.200700522

    View details for Web of Science ID 000247558200017

    View details for PubMedID 17506056

  • Guanidine and amidine organocatalysts for ring-opening polymerization of cyclic esters MACROMOLECULES Lohmeijer, B. G., Pratt, R. C., Leibfarth, F., Logan, J. W., Long, D. A., Dove, A. P., Nederberg, F., Choi, J., Wade, C., Waymouth, R. M., Hedrick, J. L. 2006; 39 (25): 8574-8583

    View details for DOI 10.1021/ma0619381

    View details for Web of Science ID 000242515800007

  • Well-controlled living polymerization of perylene-labeled polyisoprenes and their use in single-molecule Imaging MACROMOLECULES Gavranovic, G. T., Csihony, S., Bowden, N. B., Hawker, C. J., Waymouth, R. M., Moerner, W. E., Fuller, G. G. 2006; 39 (23): 8121-8127

    View details for DOI 10.1021/ma0612475

    View details for Web of Science ID 000241813200046

  • Exploration, optimization, and application of supramolecular thiourea-amine catalysts for the synthesis of lactide (co)polymers MACROMOLECULES Pratt, R. C., Lohmeijer, B. G., Long, D. A., Lundberg, P. N., Dove, A. P., Li, H., Wade, C. G., Waymouth, R. M., Hedrick, J. L. 2006; 39 (23): 7863-7871

    View details for DOI 10.1021/ma061607o

    View details for Web of Science ID 000241813200016

  • Effects of temperature and chemical modification on polymer Langmuir films JOURNAL OF PHYSICAL CHEMISTRY B Gavranovic, G. T., Smith, M. M., Jeong, W., Wong, A. Y., Waymouth, R. M., Fuller, G. G. 2006; 110 (44): 22285-22290

    Abstract

    We previously reported on a rheological study of Langmuir films of poly(tert-butyl methacrylate) (PtBMA), and this work describes further studies on this system. Here, surface pressure-area (Pi-A) isotherms and interfacial shear rheology experiments are performed to better understand the effects of two modifications: varying the temperature between 5 and 40 degrees C and introducing small amounts of carboxylic acid groups by partially hydrolyzing the polymer. Increased temperature produced isotherms with lower plateau surface pressures, Pip, and Pi values shifted to lower areas above Pip. Film properties transition from being primarily viscous to being dominated by elasticity as Pip is crossed for all temperatures studied, even as the value of Pip changes. Increasing the hydrolysis fraction leads to isotherms shifted to lower areas throughout the curve and higher Pip values. Both temperature variation and chemical modification are believed to affect the relative importance of polymer-polymer and polymer-subphase interactions.

    View details for DOI 10.1021/jp063396v

    View details for Web of Science ID 000241729300034

    View details for PubMedID 17078671

  • Organocatalytic living ring-opening polymerization of cyclic carbosiloxanes ORGANIC LETTERS Lohmeijer, B. G., Dubois, G., Leibfarth, F., Pratt, R. C., Nederberg, F., Nelson, A., Waymouth, R. M., Wade, C., Hedrick, J. L. 2006; 8 (21): 4683-4686

    Abstract

    [reaction: see text] An organocatalytic route to narrowly dispersed poly(carbosiloxanes) of predictable molecular weight and end group fidelity is described. N-Heterocyclic carbenes (NHC) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) catalyze the ring opening of cyclic carbosiloxanes. The pK(b) of the catalyst is important in preventing adverse transetherification reactions and obtaining well-defined polymers. Mechanistic studies indicate that hydrogen bonding to TBD or the NHC activates alcohols or silanols for ring-opening reactions.

    View details for DOI 10.1021/ol0614166

    View details for Web of Science ID 000241030900004

    View details for PubMedID 17020277

  • POLY 612-Organocatalytic polymerization of ethylene oxide and the controlled synthesis of PEO-based hydrogel networks Mason, A. F., Lohmeijer, B. G., Li, H., Pratt, R. C., Liao, Q., Frank, C. W., Kingsbury, K., Waymouth, R. M., Hedrick, J. L. AMER CHEMICAL SOC. 2006
  • POLY 264-Organocatalytic ring opening polymerization: Activation through hydrogen bonding Lohmeijer, B. G., Pratt, R. C., Li, H., Dove, A. P., Nederberg, F., Mason, A. F., Eade, G. F., Choi, J., Waymouth, R. M., Wade, C., HEDRICK, J. L. AMER CHEMICAL SOC. 2006
  • POLY 407-Organocatalysis: A powerful strategy for controlled polymerization reactions Waymouth, R. M., Hedrick, J. L., Culkin, D. A., Pratt, R. C., Jeong, W., Kamber, N. E., Lohmeijer, B. G., Coulembier, O. AMER CHEMICAL SOC. 2006
  • PMSE 337-Covalently tailoring the surface properties of a self-assembling protein scaffold for materials applications Jeong, W., Culkin, D. A., Coulembier, O., Hedrick, J. L., Waymouth, R. M. AMER CHEMICAL SOC. 2006: 315-315
  • PMSE 617-Effect of counterions on the liquid properties of aqueous polyurethane dispersions prepared through the acetone process Nederberg, F., Lohmeijer, B. G., Pratt, R. C., Mason, A. F., Eade, G., Choi, J., Balsara, N. P., Waymouth, R. M., HEDRICK, J. L. AMER CHEMICAL SOC. 2006: 247-247
  • POLY 261-N-heterocyclic carbenes as organocatalysts for the ring-opening polymerization of e-caprolactone Kamber, N. E., Kiesewetter, M. K., Hedrick, J. L., Waymouth, R. M. AMER CHEMICAL SOC. 2006
  • POLY 646-Organocatalytic ring-opening polymerizations of morpholine-2,6-diones: A route to functionalized poly(lactide)s and pseudopeptides Pratt, R. C., Lohmeijer, B. G., Mason, A. F., Waymouth, R. M., Hedrick, J. L. AMER CHEMICAL SOC. 2006
  • Alcohol adducts of N-heterocyclic carbenes: Latent catalysts for the thermally-controlled living polymerization of cyclic esters MACROMOLECULES Coulembier, O., Lohmeijer, B. G., Dove, A. P., Pratt, R. C., Mespouille, L., Culkin, D. A., Benight, S. J., Dubois, P., Waymouth, R. M., Hedrick, J. L. 2006; 39 (17): 5617-5628

    View details for DOI 10.1021/ma0611366

    View details for Web of Science ID 000239758400009

  • Monolayered organosilicate toroids and related structures: A phase diagram for templating from block copolymers NANO LETTERS Choi, J., Hermans, T. M., Lohmeijer, B. G., Pratt, R. C., Dubois, G., Frommer, J., Waymouth, R. M., Hedrick, J. L. 2006; 6 (8): 1761-1764

    Abstract

    Here we report the controlled generation of micelle-templated organosilicate nanostructures resulting from self-assembly of a block copolymer/organosilicate mixture followed by organosilicate vitrification and copolymer thermolysis. Variation of solution condition and the copolymer/organosilicate mixture composition generates widely different film morphologies ranging from toroids to linear features to contiguous nanoporous monolayers. The use of reactive organosilicates for block copolymer templation generates functional inorganic nanostructures with thermal and mechanical stability.

    View details for DOI 10.1021/nl0612906

    View details for Web of Science ID 000239623900033

    View details for PubMedID 16895370

  • Density functional theory calculations of Ti-TEMPO complexes: Influence of ancillary Ligation on the strength of the Ti-O bond ORGANOMETALLICS Huang, K., Han, J. H., Musgrave, C. B., Waymouth, R. M. 2006; 25 (14): 3317-3323

    View details for DOI 10.1021/om060148c

    View details for Web of Science ID 000238534400008

  • Metal-free catalyzed ring-opening polymerization of, beta-lactones: Synthesis of amphiphilic triblock copolymers based on poly(dimethylmalic acid) MACROMOLECULES Coulembier, O., Mespouille, L., Hedrick, J. L., Waymouth, R. M., Dubois, P. 2006; 39 (12): 4001-4008

    View details for DOI 10.1021/ma060552n

    View details for Web of Science ID 000238051600008

  • Metal and ligand K-edge XAS of titanium-TEMPO complexes: Determination of oxidation states and insights into Ti-O bond homolysis INORGANIC CHEMISTRY George, S. D., Huang, K., Waymouth, R. M., Solomon, E. I. 2006; 45 (11): 4468-4477

    Abstract

    Ti-TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) provides a means for generating Ti(III) complexes by homolysis of the Ti-O bond. It has been determined that bis-Cp-Ti-TEMPO complexes readily undergo homolytic cleavage while the mono-Cp-Ti-TEMPO complexes do not. Here Ti K- and Cl K-edge XAS are applied to directly determine the oxidation state of TiCl3TEMPO, TiCpCl2TEMPO, and TiCp2ClTEMPO, with reference to Ti(III) and Ti(IV) complexes of known oxidation state. The Ti K-edge data show that Ti(III) complexes exhibit a pre-edge feature approximately 1 eV lower than any of the Ti(IV) complexes; while the Cl K-edges show that Ti(III) complexes have a Cl K- pre-edge feature to approximately 1 eV higher energy than any of the Ti(IV) complexes. Taken together, the Ti and Cl K-edge data indicate that the Ti-TEMPO complexes are best described as Ti(IV)-TEMPO anions (rather than Ti(III)-nitroxyl radicals). In addition, the Cl K-edges indicate that replacement of Cl by Cp weakens the bonding with the remaining ligands, with the Cl 3p covalency decreasing from 25% to 21% to 17% on going from TiCl3TEMPO to TiCpCl2TEMPO to TiCp2ClTEMPO. DFT calculations also show that the electronic structures of the Ti-TEMPO complexes are modulated by the replacement of chloride by Cp. The effect of the Cp on the ancillary ligation is one factor that contributes to facile Ti-O bond homolysis in TiCp2ClTEMPO. However, the results indicate the primary contribution to the energetics of Ti-O bond homolysis in TiCp2ClTEMPO is stabilization of the three-coordinate product by Cp.

    View details for DOI 10.1021/ic060402t

    View details for Web of Science ID 000237690700029

    View details for PubMedID 16711697

  • N-Heterocyclic carbenes: Effective organic catalysts for living polymerization POLYMER Dove, A. P., Pratt, R. C., Lohmeijer, B. G., Culkin, D. A., Hagberg, E. C., Nyce, G. W., Waymouth, R. M., Hedrick, J. L. 2006; 47 (11): 4018-4025
  • Triazabicyclodecene: A simple bifunctional organocatalyst for acyl transfer and ring-opening polymerization of cyclic esters JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Pratt, R. C., Lohmeijer, B. G., Long, D. A., Waymouth, R. M., Hedrick, J. L. 2006; 128 (14): 4556-4557

    Abstract

    1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) is an effective organocatalyst for acyl transfer as well as the ring-opening polymerization of cyclic esters. Its high activity is attributed to its ability to simultaneously activate both esters and alcohols, as demonstrated in a model reaction. This unique mechanism makes TBD a remarkably simple example of a bifunctional catalyst. The simplicity of the reaction conditions, the ready commercial availability of the catalyst, and its high activity provide an accessible methodology to allow future studies of tailor-made polyesters.

    View details for DOI 10.1021/ja060662+

    View details for Web of Science ID 000236770300030

    View details for PubMedID 16594676

  • Synthesis, structure, and polymerization activity of a titanium complex with a chelating [(hydroxy-kappa O)amino-kappa N]phenolato(2-)-kappa O ligand HELVETICA CHIMICA ACTA Kraft, B. M., Huang, K., Cole, A. P., Waymouth, R. M. 2006; 89 (8): 1589-1595
  • Stereoselective polymerization of rac- and meso-lactide catalyzed by sterically encumbered N-heterocyclic carbenes CHEMICAL COMMUNICATIONS Dove, A. P., Li, H., Pratt, R. C., Lohmeijer, B. G., Culkin, D. A., Waymouth, R. M., Hedrick, J. L. 2006: 2881-2883

    Abstract

    New sterically encumbered N-heterocyclic carbene catalysts were synthesized and used to polymerize rac-lactide to give highly isotactic polylactide or meso-lactide to give heterotactic polylactide.

    View details for DOI 10.1039/b601393g

    View details for Web of Science ID 000239251200014

    View details for PubMedID 17007404

  • Application of solvent-directed assembly of block copolymers to the synthesis of nanostructured materials with low dielectric constants ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Hermans, T. M., Choi, J., Lohmeijer, B. G., Dubois, G., Pratt, R. C., Kim, H., Waymouth, R. M., Hedrick, J. L. 2006; 45 (40): 6648-6652

    View details for DOI 10.1002/anie.200601888

    View details for Web of Science ID 000241474500009

    View details for PubMedID 16906604

  • Dynamic NMR studies of cationic bis(2-phenylindenyl) zirconium pyridyl complexes: Evidence for syn conformers in solution ORGANOMETALLICS Lincoln, A. L., Wilmes, G. M., Waymouth, R. M. 2005; 24 (24): 5828-5835

    View details for DOI 10.1021/om050473k

    View details for Web of Science ID 000233378900010

  • Thiourea-based bifunctional organocatalysis: Supramolecular recognition for living polymerization JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Dove, A. P., Pratt, R. C., Lohmeijer, B. G., Waymouth, R. M., Hedrick, J. L. 2005; 127 (40): 13798-13799

    Abstract

    A versatile, metal-free, organocatalytic approach to the living ring-opening polymerization of lactide using a bifunctional thiourea-tertiary amine catalyst is described. Mild and highly selective polymerization conditions produced poly(lactides) with predictable molecular weights and extremely narrow polydispersities ( approximately 1.05), characteristic of a living polymerization. The extraordinary selectivity of this catalyst system for polymerization relative to transesterification is remarkably unusual. The low polydispersities and exceptional control observed are a consequence of selective transesterification of lactide relative to the open chain esters. Presumably, the ring strain of lactide provides both a driving force for the polymerization and a kinetic preference for polymerization relative to transesterification with catalyst. We postulate that the initiating/propagating alcohol is activated by acid-base interaction with the tertiary amine moiety and the carbonyl of the lactide monomer is simultaneously activated by hydrogen bonding to the thiourea moiety of the catalyst.

    View details for DOI 10.1021/ja0543346

    View details for Web of Science ID 000232413300028

    View details for PubMedID 16201794

  • [H(OEt2)(2)](+) and [Ph3C](+) salts of the borate anions [B(CF3)(4)](-), [(CF3)(3)BCN](-), and [B(CN)(4)](-) ORGANOMETALLICS Finze, M., Bernhardt, E., Berkei, M., Willner, H., Hung, J., Waymouth, R. M. 2005; 24 (21): 5103-5109

    View details for DOI 10.1021/om050463j

    View details for Web of Science ID 000232387800034

  • Unconstrained geometry complexes: Ethylene/alpha-olefin copolymerizations with a tetramethyldisilyl-bridged Cp-amido titanium complex JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY Hung, J., Waymouth, R. M. 2005; 43 (17): 3840-3851

    View details for DOI 10.1002/pola.20862

    View details for Web of Science ID 000231369700014

  • Single-component catalyst/initiators for the organocatalytic ring-opening polymerization of lactide JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Csihony, S., Culkin, D. A., Sentman, A. C., Dove, A. P., Waymouth, R. M., Hedrick, J. L. 2005; 127 (25): 9079-9084

    Abstract

    The synthesis and characterization of a series of primary and secondary alcohol adducts of 1,3-dimesitylimidazolin-2-ylidene is described. These adducts are stable as solids at room temperature, but readily release alcohol and the free carbene in solution. These alcohol adducts function as excellent single-component catalyst/initiators for the ring-opening polymerization of lactide under mild conditions, providing polymers with controlled molecular weights and narrow polydispersities. Multifunctional adducts were used to prepare poly(lactide)s of more complex architectures.

    View details for Web of Science ID 000230010600049

    View details for PubMedID 15969586

  • Amine bis(phenolate) zirconium complexes: Influence of ligand structure and cocatalyst on copolymerization behavior MACROMOLECULES Reybuck, S. E., Lincoln, A. L., Ma, S. D., Waymouth, R. M. 2005; 38 (7): 2552-2558

    View details for DOI 10.1021/ma0476386

    View details for Web of Science ID 000228067600005

  • Homolysis of weak Ti-O bonds: Experimental and theoretical studies of titanium oxygen bonds derived from stable nitroxyl radicals JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Huang, K. W., Han, J. H., Cole, A. P., Musgrave, C. B., Waymouth, R. M. 2005; 127 (11): 3807-3816

    Abstract

    Titanium-oxygen bonds derived from stable nitroxyl radicals are remarkably weak and can be homolyzed at 60 degrees C. The strength of these bonds depends sensitively on the ancillary ligation at titanium. Direct measurements of the rate of Ti-O bond homolysis in Ti-TEMPO complexes Cp2TiCl(TEMPO) (3) and Cp2TiCl(4-MeO-TEMPO) (4) (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl, 4-MeO-TEMPO = 2,2,6,6-tetramethyl-4-methoxypiperidine-N-oxyl) were conducted by nitroxyl radical exchange experiments. Eyring plots gave the activation parameters, deltaH++ = 27(+/- 1) kcal/mol, deltaS++ = 6.9(+/- 2.3) eu for 3 and deltaH++ = 28(+/- 1) kcal/mol, deltaS++ = 9.0(+/- 3.0) eu for 4, consistent with a process involving the homolysis of a weak Ti-O bond to generate the transient Cp2Ti(III)Cl and the nitroxyl radical. Thermolysis of the titanocene TEMPO complexes in the presence of epoxides leads to the Cp2Ti(III)Cl-mediated ring-opening of the epoxide followed by trapping by the nitroxyl radical. The X-ray crystal structure of the Ti-TEMPO derivative, Cp2TiCl(4-MeO-TEMPO) (4), is reported. DFT (B3LYP/6-31G*) calculations and experimental studies reveal that the strength of the Ti-O bond decreases dramatically with the number of cyclopentadienyl groups on titanium. The calculated Ti-O bond strength of the monocyclopentadienyl complex 2 is 43 kcal/mol, whereas that of the biscyclopentadienyl complex 3 is 17 kcal/mol, a difference of 26 kcal/mol. These studies reveal that the strength of these Ti-O bonds can be tuned over an interesting and experimentally accessible temperature range by appropriate ligation on titanium.

    View details for DOI 10.1021/ja044512f

    View details for Web of Science ID 000227738700047

    View details for PubMedID 15771515

  • Silver(I)-carbene complexes/ionic liquids: Novel N-heterocyclic carbene delivery agents for organocatalytic transformations JOURNAL OF ORGANIC CHEMISTRY Sentman, A. C., Csihony, S., Waymouth, R. M., Hedrick, J. L. 2005; 70 (6): 2391-2393

    Abstract

    [reaction: see text] N-Heterocyclic carbene (NHC) complexes with silver were investigated as sources of unsaturated NHC carbene catalysts via thermal decomposition. The NHC complex (1-ethyl-3-methylimidazol-2-ylidene)silver(I) chloride is an ionic liquid, and was found to catalyze the ring-opening polymerization of lactide at elevated temperatures to give narrowly dispersed polylactide of predictable molecular weight. Silver-carbene complexes can also be used for the catalysis of small molecule transesterification reactions. Thermolysis of the silver complexes in the presence of CS(2) yielded the zwitterionic CS(2) adducts of the carbene, implicating the intermediacy of the free carbene in these reactions.

    View details for DOI 10.1021/jo048555q

    View details for Web of Science ID 000227566400067

    View details for PubMedID 15760240

  • Latent, thermally activated organic catalysts for the on-demand living polymerization of lactide ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Coulembier, O., Dove, A. P., Pratt, R. C., Sentman, A. C., Culkin, D. A., Mespouille, L., Dubois, P., Waymouth, R. M., HEDRICK, J. L. 2005; 44 (31): 4964-4968

    View details for DOI 10.1002/anie.200500723

    View details for Web of Science ID 000231185400029

    View details for PubMedID 16007717

  • Synthesis, structure, and olefin polymerization with nickel(II) N-heterocyclic carbene enolates CHEMICAL COMMUNICATIONS Ketz, B. E., Ottenwaelder, X. G., Waymouth, R. M. 2005: 5693-5695

    Abstract

    Two novel N-heterocylic carbene enolate nickel complexes have been prepared and shown to be active for ethylene and propylene polymerization to yield linear polymers.

    View details for DOI 10.1039/b511202h

    View details for Web of Science ID 000233458800029

    View details for PubMedID 16292393

  • Cyclopentadienyl titanium hydroxylaminato complexes as highly active catalysts for the polymerization of propylene CHEMICAL COMMUNICATIONS Dove, A. P., Xie, X. J., Waymouth, R. M. 2005: 2152-2154

    Abstract

    Half sandwich complexes of titanium bearing eta1 or eta2 bound nitroxide ligands are highly active catalysts for the polymerisation of propylene to high molecular weight atactic poly(propylene).

    View details for DOI 10.1039/b418778d

    View details for Web of Science ID 000228559200026

    View details for PubMedID 15846430

  • A neutron scattering study of the structure and water partitioning of selectively deuterated copolymer micelles LANGMUIR Stancik, C. M., Lavoie, A. R., Achurra, P. A., Waymouth, R. M., Gast, A. P. 2004; 20 (21): 8975-8987

    Abstract

    We present a scattering study of a selectively deuterated micelle-forming diblock copolymer. The copolymer comprises a partially deuterated polystyrene (d,h-PS) block and an imidazolium-functionalized PS (IL) block. In toluene solutions, the copolymers assemble into elongated micelles where the IL block forms the micelle core. Through dynamic light scattering (DLS) measurements, we obtain the overall size of the micelles. In our small-angle neutron scattering (SANS) studies, we use contrast matching to characterize the IL core and the PS shell of the micelles independently. The PS block forming the micelle shell exhibits either a starlike or brushlike conformation depending upon the size of the core to which it is tethered. We find the IL block to be in an extended conformation, driving the formation of slightly elongated and relatively stiff micelle cores. The elongated micelle core cross-sectional radius and length depend linearly on the length of the IL block. We find that the micelles can sequester a few water molecules for each IL repeat unit; the addition of water slightly increases the cross section of the elongated micelles.

    View details for DOI 10.1021/la0364183

    View details for Web of Science ID 000224391600008

    View details for PubMedID 15461476

  • A general and versatile approach to thermally generated N-heterocyclic carbenes CHEMISTRY-A EUROPEAN JOURNAL Nyce, G. W., Csihony, S., Waymouth, R. M., HEDRICK, J. L. 2004; 10 (16): 4073-4079

    Abstract

    The synthesis of N-heterocyclic carbene (NHC) adducts by condensation of diamines with appropriately substituted benzaldehydes is described. This simplified approach provides the NHC adduct without first having to generate the carbene followed by its protection. These adducts undergo thermal deprotection to generate N-heterocyclic carbene in situ. Adduct decomposition temperatures were investigated as a function of catalyst structure by using thermal analysis and spectroscopic techniques. Importantly, unlike adducts derived from chloroform, the new pentafluorobenzene-based adducts are more readily prepared and are stable at room temperature. The utility of these adducts as organic catalyst precursors for living ring-opening polymerization (ROP) of lactide, transesterification reactions, and the synthesis of N-heterocyclic carbene ligated organometallic complexes is also described.

    View details for DOI 10.1002/chem.200400196

    View details for Web of Science ID 000223593400023

    View details for PubMedID 15317058

  • Catalytic syntheses of alternating, stereoregular ethylene/cycloolefin copolymers TETRAHEDRON Lavoie, A. R., Waymouth, R. M. 2004; 60 (34): 7147-7155
  • Bredereck's reagent revisited: Latent anionic ring-opening polymerization and transesterification reactions ADVANCED SYNTHESIS & CATALYSIS Csihony, S., Beaudette, T. T., Sentman, A. C., Nyce, G. W., Waymouth, R. M., Hedrick, J. L. 2004; 346 (9-10): 1081-1086
  • Ethylene/1-hexene copolymerization with tetramethyldisiloxane-bridged bis(indenyl) metallocenes JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY Reybuck, S. E., Waymouth, R. M. 2004; 42 (13): 3323-3331

    View details for DOI 10.1002/pola.20170

    View details for Web of Science ID 000222124600021

  • Structure and reactivity of an allylpalladium N-heterocyclic carbene enolate complex ORGANOMETALLICS Ketz, B. E., Cole, A. P., Waymouth, R. M. 2004; 23 (12): 2835-2837

    View details for DOI 10.1021/om049838b

    View details for Web of Science ID 000221773600003

  • Effects of ligand substitutions on the rotation rate of indenyl ligands in bis(2-arylindenyl)zirconocenes by NMR line-shape analysis and relaxation in the rotating frame ORGANOMETALLICS Wilmes, G. M., France, M. B., Lynch, S. R., Waymouth, R. M. 2004; 23 (10): 2405-2411

    View details for DOI 10.1021/om034166v

    View details for Web of Science ID 000221231100027

  • Investigation of bridge and 2-phenyl substituent effects on ethylene/alpha-olefin copolymerization behavior with 1,2 '-Bridged bis(indenyl)zirconium dichlorides MACROMOLECULES Reybuck, S. E., Waymouth, R. M. 2004; 37 (7): 2342-2347

    View details for DOI 10.1021/ma035365t

    View details for Web of Science ID 000220581700004

  • Silver(I)-carbene complexes ionic liquids: Novel N-heterocyclic carbene delivery agents for living polymerization Sentman, A., Csihony, S., Nyce, G. W., Waymouth, R. M., HEDRICK, J. L. AMER CHEMICAL SOC. 2004: U456-U456
  • Synthesis, structure, and reactivity of hydroxylaminato alkyltitanium complexes ORGANOMETALLICS Mahanthappa, M. K., Cole, A. P., Waymouth, R. M. 2004; 23 (6): 1405-1410

    View details for DOI 10.1021/om0305521

    View details for Web of Science ID 000220093200035

  • Synthesis, structure, and ethylene/alpha-olefin polymerization behavior of (cyclopentadienyl),(nitroxide)titanium complexes ORGANOMETALLICS Mahanthappa, M. K., Cole, A. P., Waymouth, R. M. 2004; 23 (4): 836-845

    View details for DOI 10.1021/om034096s

    View details for Web of Science ID 000188872700026

  • Heterogeneous composition and microstructure of elastomeric polypropylene from a sterically hindered 2-arylindenylhafnium catalyst MACROMOLECULES Wiyatno, W., Chen, Z. R., Liu, Y. X., Waymouth, R. M., Krukonis, V., Brennan, K. 2004; 37 (3): 701-708

    View details for DOI 10.1021/ma020332j

    View details for Web of Science ID 000188803000006

  • Micelles of imidazolium-functionalized polystyrene diblock copolymers investigated with neutron and light scattering LANGMUIR Stancik, C. M., Lavoie, A. R., Schutz, J., Achurra, P. A., Lindner, P., Gast, A. P., Waymouth, R. M. 2004; 20 (3): 596-605

    Abstract

    We synthesize a series of block copolymers comprising a polystyrene (PS) block and an imidazolium-functionalized PS (IL) block and characterize their assembly properties. We use small-angle neutron scattering and dynamic light scattering to determine the micelle size and shape in dilute solutions and to assess the micelle interactions in concentrated solutions. By studying a series of copolymers with fixed PS block length, we find that the length of the IL block governs the micelle dimensions. Our data suggest that these copolymers form elongated micelle structures where the IL block is extended in the micelle core. We find that these micelles can sequester water and that interactions between the micelles lead to structure factor peaks at elevated concentrations.

    View details for DOI 10.1021/la0353632

    View details for Web of Science ID 000188660600013

    View details for PubMedID 15773081

  • Hydrolysis of CpTiCl2(TEMPO) and its application on one-pot syntheses of CpTiCl(OR)(2) complexes DALTON TRANSACTIONS Huang, K. W., Waymouth, R. M. 2004: 354-356

    Abstract

    The eta1-hydroxylamido half-titanocene complex, CpTiCl2(TEMPO) 1, hydrolyzes extremely efficiently to generate (CpTiClO)4 and the protonated hydroxylamine. The efficient hydrolysis chemistry provides selective syntheses of CpTi dialkoxide and diaryloxide complexes.

    View details for DOI 10.1039/b314027j

    View details for Web of Science ID 000188433900002

    View details for PubMedID 15252536

  • Propylene polymerization with 1,2 '-bridged bis(indenyl)zirconium dichlorides MACROMOLECULES Finze, M., Reybuck, S. E., Waymouth, R. M. 2003; 36 (25): 9325-9334

    View details for DOI 10.1021/ma0303972

    View details for Web of Science ID 000187178000012

  • The dual-site alternating cyclocopolymerization of 1,3-butadiene with ethylene JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Choo, T. N., Waymouth, R. M. 2003; 125 (30): 8970-8971

    Abstract

    The copolymerization of ethylene with 1,3-butadiene was studied with the series of ansa-metallocenes Me2Si(Cp)(9-Flu)ZrCl2 (1), Me2Si(1-Ind)(9-Flu)ZrCl2 (2), and Me2Si(9-Flu)2ZrCl2 (3) with methylaluminoxane (MAO) as cocatalyst. The catalyst 2/MAO yields a cyclocopolymer composed of two ethylene monomer units for every one butadiene in a novel periodic architecture of 1,2-enchained cyclopentane units separated by three methylenes. The high butadiene content in the copolymer and the high selectivity for alternating cyclocopolymerization to form methylene-1,2-cyclopentane units implicate a dual-site mechanism where butadiene and ethylene are enchained at different coordination sites.

    View details for DOI 10.1021/ja034903x

    View details for Web of Science ID 000184364500002

    View details for PubMedID 15369326

  • Synthesis and characterization of [TiF2(NMe2)(2)](4) and its use for olefin polymerizations INORGANICA CHIMICA ACTA Straus, D. A., Kamigaito, M., Cole, A. P., Waymouth, R. M. 2003; 349: 65-68
  • High comonomer selectivity in ethylene/hexene copolymerization by unbridged indenyl metallocenes MACROMOLECULES Dankova, M., Waymouth, R. M. 2003; 36 (11): 3815-3820

    View details for DOI 10.1021/ma021075l

    View details for Web of Science ID 000183247700012

  • Sequence and stereoselectivity of the C-1-symmetric metallocene Me2Si(1-(4,7-Me(2)Ind))(9-Flu)ZrCl2 MACROMOLECULES Fan, W., Waymouth, R. M. 2003; 36 (9): 3010-3014

    View details for DOI 10.1021/ma020037z

    View details for Web of Science ID 000182646600006

  • In vitro epithelialization of a synthetic polymer for generation of corneal onlay/keratoprosthesis Pilyugina, S. A., Lavoie, A., Huie, P., Derr, K., SMITH, A. J., Noolandi, J., Waymouth, R. M., Ta, C. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2003: U321-U321
  • Nucleation and crystallization of low-crystallinity polypropylene followed in situ by hot stage atomic force microscopy MACROMOLECULES Schonherr, H., Waymouth, R. M., Frank, C. W. 2003; 36 (7): 2412-2418

    View details for DOI 10.1021/ma0208335

    View details for Web of Science ID 000182045800031

  • Control of sequence distribution of ethylene copolymers: Influence of comonomer sequence on the melting behavior of ethylene copolymers MACROMOLECULES Hung, J., Cole, A. P., Waymouth, R. A. 2003; 36 (7): 2454-2463

    View details for DOI 10.1021/ma021779v

    View details for Web of Science ID 000182045800036

  • In situ generation of carbenes: A general and versatile platform for organocatalytic living polymerization JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Nyce, G. W., Glauser, T., CONNOR, E. F., Mock, A., Waymouth, R. M., Hedrick, J. L. 2003; 125 (10): 3046-3056

    Abstract

    A metal-free, organocatalytic approach to living polymerization using N-heterocyclic carbenes as nucleophilic catalysts generated and used in situ in a single-pot process is detailed. The N-heterocyclic carbene catalyst platform is extremely versatile, as the nature of the substituents has a pronounced effect of catalyst stability and activity toward different substrates. The generation of imidazolium- and thiazaolium-based carbenes was accomplished from the reaction of the corresponding salts with the appropriate bases. This allowed the rapid screening of libraries of catalysts that provided a basic understanding of catalyst structure (sterics, electronics, etc.) with the polymerization rate, control, substrate, and range of molecular weights. The imidazole-based catalysts were significantly more active toward ROP than the thiazolium-based analogues. No appreciable differences between imidazol-2-ylidene and imidazolin-2-ylidene catalysts were observed. Less sterically demanding carbenes were found to be more active toward ring-opening polymerization (ROP) than their sterically encumbered analogues for lactone polymerization. These data prompted the investigation of ionic liquid as a precatalyst reservoir in a phase-transfer polymerization with an immiscible THF solution of monomer and initiator. In situ activation of the ionic liquid generates carbene that migrates to the organic phase effecting living ROP. Precatalyst (ionic liquid) regeneration terminates polymerization. This simple reaction/recycle protocol readily allows repetitive ROPs from the ionic liquid using commercially available materials.

    View details for DOI 10.1021/ja021084+

    View details for Web of Science ID 000181409500051

    View details for PubMedID 12617671

  • Component stress-strain behavior and small-angle neutron scattering investigation of stereoblock elastomeric polypropylene MACROMOLECULES Wiyatno, W., Fuller, G. G., Pople, J. A., Gast, A. P., Chen, Z. R., Waymouth, R. M., Myers, C. L. 2003; 36 (4): 1178-1187

    View details for DOI 10.1021/na020477q

    View details for Web of Science ID 000181117200032

  • Ring opening metathesis polymerization on non-covalently functionalized single-walled carbon nanotubes CHEMICAL COMMUNICATIONS Gomez, F. J., Chen, R. J., Wang, D. W., Waymouth, R. M., Dai, H. J. 2003: 190-191

    Abstract

    Norbornene polymerization has been initiated selectively on the surface of single-walled carbon nanotubes (SWNTs) via a specifically adsorbed pyrene-linked ROMP initiator, resulting in a homogeneous non-covalent poly(norbornene) coating.

    View details for DOI 10.1039/b211194b

    View details for Web of Science ID 000180249600008

    View details for PubMedID 12585385

  • Alternating stereospecific copolymerization of cyclopentene and ethylene with constrained geometry catalysts CHEMICAL COMMUNICATIONS Lavoie, A. R., Ho, M. H., Waymouth, R. M. 2003: 864-865

    Abstract

    The stereoselective copolymerization of cyclopentene (cP) and ethylene (E) to generate highly alternating polymers with isotactic cis 1,2-cyclopentene enchainment is reported.

    View details for DOI 10.1039/b300841j

    View details for Web of Science ID 000181774700025

    View details for PubMedID 12739650

  • Synthesis of polyethylene graft block copolymers from styrene, butyl acrylate, and butadiene MACROMOLECULES Bowden, N. B., Dankova, M., Wiyatno, W., Hawker, C. J., Waymouth, R. M. 2002; 35 (25): 9246-9248

    View details for DOI 10.1021/ma020544g

    View details for Web of Science ID 000179623200002

  • Dynamic response of stereoblock elastomeric polypropylene studied by rheooptics and X-ray scattering. 1. Influence of isotacticity MACROMOLECULES Wiyatno, W., Pople, J. A., Gast, A. P., Waymouth, R. M., Fuller, G. G. 2002; 35 (22): 8488-8497

    View details for DOI 10.1021/ma020261o

    View details for Web of Science ID 000178738000033

  • Dynamic response of stereoblock elastomeric polypropylene studied by rheooptics and X-ray scattering. 2. Orthogonally oriented crystalline chains MACROMOLECULES Wiyatno, W., Pople, J. A., Gast, A. P., Waymouth, R. M., Fuller, G. G. 2002; 35 (22): 8498-8508

    View details for DOI 10.1021/ma020262g

    View details for Web of Science ID 000178738000034

  • Expanding the catalytic activity of nucleophilic N-heterocyclic carbenes for transesterification reactions ORGANIC LETTERS Nyce, G. W., Lamboy, J. A., CONNOR, E. F., Waymouth, R. M., Hedrick, J. L. 2002; 4 (21): 3587-3590

    Abstract

    [reaction: see text] Currently, there is a renewed interest in reactions that are catalyzed by organic compounds. Typical organic catalysts for acylation or transesterification reactions are based on either nucleophilic tertiary amines or phosphines. This communication discusses the use of nucleophilic N-heterocyclic carbenes as efficient transesterification catalysts. These relatively unexplored and highly versatile organic catalysts were found to be mild, selective, and more active than traditional organic nucleophiles.

    View details for DOI 10.1021/ol0267228

    View details for Web of Science ID 000178522700010

    View details for PubMedID 12375894

  • Synthesis of fluorescently labeled polymers and their use in single-molecule imaging MACROMOLECULES Bowden, N. B., Willets, K. A., Moerner, W. E., Waymouth, R. M. 2002; 35 (21): 8122-8125

    View details for DOI 10.1021/ma020780r

    View details for Web of Science ID 000178444400037

  • 2-arylindene metallocenes: Conformationally dynamic catalysts to control the structure and properties of polypropylenes ACCOUNTS OF CHEMICAL RESEARCH Lin, S., Waymouth, R. M. 2002; 35 (9): 765-773

    Abstract

    Polymerization of propylene with catalysts derived from unbridged 2-arylindene metallocenes leads to elastomeric, low-tacticity polypropylenes. The polymerization behavior of these conformationally dynamic catalyst systems is interpreted in terms of a multistate mechanism where the catalyst enchains the monomer from both stereoselective and nonstereoselective conformations during the lifetime of a single polymer chain. The structure and properties of the polypropylenes depend sensitively on the metallocene and the polymerization conditions (temperature, pressure, monomer concentration); samples of low to intermediate isotacticity ([mmmm] = 20-40%) are elastomeric, with low densities and broad melting ranges that extend to 150 degrees C. Samples of higher tacticity ([mmmm] = 40-70%) behave as softened thermoplastics.

    View details for DOI 10.1021/ar010081j

    View details for Web of Science ID 000178085700010

    View details for PubMedID 12234206

  • Influence of cocatalyst on the stereoselectivity of unbridged 2-phenylindenyl metallocene catalysts MACROMOLECULES Wilmes, G. M., Polse, J. L., Waymouth, R. M. 2002; 35 (18): 6766-6772

    View details for DOI 10.1021/ma020512t

    View details for Web of Science ID 000177688800008

  • Synthesis of polyethylene graft block copolymers from butyl acrylate, styrene, and butadiene. Bowden, N. B., Waymouth, R. M., Dankova, M., Wiyatno, W. AMER CHEMICAL SOC. 2002: U153-U153
  • Rotation rates of bis(2-arylindenyl)zirconocenes: Effects of ligands and implications for formation of stereoblock polypropylene. Wilmes, G. M., France, M. B., Lynch, S. R., Waymouth, R. M. AMER CHEMICAL SOC. 2002: U685-U686
  • Coordination chemistry of stable radicals: Homolysis of a titanium-oxygen bond JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Huang, K. W., Waymouth, R. M. 2002; 124 (28): 8200-8201

    Abstract

    Thermolysis of Cp2TiCl(TEMPO) (TEMPO = 2,2,6,6-tetramethylpiperidine-1-oxyl) at 60 degrees C in a benzene/CCl4 mixture generates Cp2TiCl2. Kinetic studies implicate a mechanism involving the reversible cleavage of a Ti-O bond to generate the TEMPO radical and Cp2TiCl, which is trapped by CCl4 to give Cp2TiCl2. The rate of this reaction is strongly inhibited by added TEMPO and increases with increasing CCl4 concentration, indicating that the coupling of TEMPO to Cp2TiCl is faster than chloride atom abstraction from CCl4.

    View details for DOI 10.1021/ja0264854

    View details for Web of Science ID 000176843200009

    View details for PubMedID 12105895

  • Propylene polymerization with sterically hindered unbridged 2-arylindene metallocenes MACROMOLECULES Wilmes, G. M., Lin, S., Waymouth, R. M. 2002; 35 (14): 5382-5387

    View details for DOI 10.1021/ma012241c

    View details for Web of Science ID 000176535600012

  • Effect of tacticity on coil dimensions and thermodynamic properties of polypropylene MACROMOLECULES Jones, T. D., Chaffin, K. A., Bates, F. S., Annis, B. K., HAGAMAN, E. W., Kim, M. H., Wignall, G. D., Fan, W., Waymouth, R. 2002; 35 (13): 5061-5068

    View details for DOI 10.1021/ma011547g

    View details for Web of Science ID 000176215500031

  • Cyclocopolymerization: A mechanistic probe for dual-site alternating copolymerization of ethylene and alpha-olefins JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Choo, T. N., Waymouth, R. M. 2002; 124 (16): 4188-4189

    Abstract

    The copolymerization of ethylene with 1,5-hexadiene or 1-hexene was studied with the series of ansa-metallocenes Me2Si(Cp)(9-Flu)ZrCl2 (1), Me2Si(1-Ind)(9-Flu)ZrCl2 (3), and Me2Si(9-Flu)2ZrCl2 (4). 1,5-Hexadiene, a monomer which requires two insertion events to be cyclopolymerized, when copolymerized with ethylene using 3/MAO, gave a copolymer with a novel architecture. When compared with the copolymerization of 1-hexene with ethylene, the observed striking differences between the two copolymers provided compelling evidence for a dual-site alternating copolymerization mechanism in both cases. The copolymerization results from 1/MAO and 4/MAO further support this.

    View details for DOI 10.1021/ja0177071

    View details for Web of Science ID 000175088600010

    View details for PubMedID 11960429

  • Syndiospecific propylene polymerization using C-1-symmetric ansa-metallocene catalysts: Substituent and bridge effects MACROMOLECULES Gomez, F. J., Waymouth, R. M. 2002; 35 (9): 3358-3368

    View details for DOI 10.1021/ma011910j

    View details for Web of Science ID 000175112100010

  • Crystallization of the alpha and gamma forms of isotactic polypropylene as a tool to test the degree of segregation of defects in the polymer chains MACROMOLECULES De Rosa, C., Auriemma, F., Circelli, T., Waymouth, R. M. 2002; 35 (9): 3622-3629

    View details for DOI 10.1021/ma0116248

    View details for Web of Science ID 000175112100045

  • Models for conformationally dynamic metallocenes. Copolymerization behavior of the unbridged metallocene (1-methyl-2-phenylindenyl)(2-phenylindenyl)zirconium dichloride MACROMOLECULES Dankova, M., Kravchenko, R. L., Cole, A. P., Waymouth, R. M. 2002; 35 (8): 2882-2891

    View details for DOI 10.1021/ma011486m

    View details for Web of Science ID 000174818600007

  • Morphology of thermoplastic elastomers: Elastomeric polypropylene MACROMOLECULES Schonherr, H., Wiyatno, W., Pople, J., Frank, C. W., Fuller, G. G., Gast, A. P., Waymouth, R. M. 2002; 35 (7): 2654-2666

    View details for DOI 10.1021/ma010959m

    View details for Web of Science ID 000174559600037

  • Copolymerization behavior of unbridged indenyl metallocenes: Substituent effects on the degree of comonomer incorporation MACROMOLECULES Reybuck, S. E., Meyer, A., Waymouth, R. M. 2002; 35 (3): 637-643

    View details for DOI 10.1021/ma011517d

    View details for Web of Science ID 000173478200011

  • Polymer synthesis - Catalysts rise to the challenge SCIENCE Gomez, F. J., Waymouth, R. M. 2002; 295 (5555): 635-636

    View details for Web of Science ID 000173560900028

    View details for PubMedID 11809956

  • Synthesis and molecular structure of titanium complexes containing a reduced TEMPO radical CHEMICAL COMMUNICATIONS Mahanthappa, M. K., Huang, K. W., Cole, A. P., Waymouth, R. M. 2002: 502-503

    Abstract

    Two titanium compounds containing monoanionic ligands derived from TEMPO were synthesized and structurally characterized, demonstrating the flexibility of the coordination modes adopted by the ligand.

    View details for Web of Science ID 000174220200052

    View details for PubMedID 12120561

  • Polystyrene-supported 2-arylindenyl zirconocene catalysts for propylene polymerization ISRAEL JOURNAL OF CHEMISTRY Diehl, S. C., Waymouth, R. M. 2002; 42 (4): 393-401
  • Titanium-mediated syndiospecific styrene polymerizations: Role of oxidation state JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Mahanthappa, M. K., Waymouth, R. M. 2001; 123 (48): 12093-12094

    View details for DOI 10.1021/ja016521j

    View details for Web of Science ID 000172591000034

    View details for PubMedID 11724621

  • Alternating copolymerization of ethylene and propylene: Evidence for selective chain transfer to ethylene MACROMOLECULES Fan, W., Waymouth, R. M. 2001; 34 (25): 8619-8625
  • Alternating stereospecific copolymerization of ethylene and propylene with metallocene catalysts JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Fan, W., Leclerc, M. K., Waymouth, R. M. 2001; 123 (39): 9555-9563

    Abstract

    The copolymerization of ethylene and propylene with bridged metallocenes Me(2)E(3-RCp)(Flu)X(2)/MAO (E = C, X = Me; E = Si, X = Cl; R = H or alkyl) was investigated. Ethylene/propylene copolymerization with metallocenes having heterotopic active sites (R =Me, i-Pr) yield alternating, isotactic ethylene/propylene copolymers with percentages of alternating EPE+PEP triads in the range of 61-76% at 50% ethylene incorporation. Both the nature of the substituent R and the bridge E influence the copolymerization behavior including the copolymerization activity, copolymer sequence distribution, molecular weight, and stereochemistry. Silicon-bridged metallocenes produce copolymers with higher activity and molecular weight but lower propylene incorporation at similar feeds than the carbon-bridged analogues. Isotactic PEPEP sequences were observed for all metallocenes, while the tacticities of the EPPE sequences varied with the bridge and the substituent on the metallocene ligand. Isotactic PEPEP sequences and atactic EPPE sequence errors in the alternating copolymers are consistent with a mechanism where the comonomers are enchained alternately at the heterotopic coordination sites of the metallocenes. Isotactic EPPE sequences are indicative of occasional multiple insertions at the stereospecific site, caused by an isomerization of the chain prior to monomer insertion (backskip).

    View details for DOI 10.1021/ja0100773

    View details for Web of Science ID 000171407800007

    View details for PubMedID 11572675

  • Rheo-optics and X-ray Scattering study of elastomeric polypropylene. Wiyatno, W., Pople, J. A., Gast, A. P., Waymouth, R., Fuller, G. G. AMER CHEMICAL SOC. 2001: U365-U365
  • Chain end functionalization in nitroxide-mediated "Living" free radical polymerizations MACROMOLECULES Harth, E., Hawker, C. J., Fan, W., Waymouth, R. M. 2001; 34 (12): 3856-3862

    View details for DOI 10.1021/ma0019297

    View details for Web of Science ID 000169049000011

  • Syndiospecific propylene polymerization with C-1 symmetric group 4 ansa-metallocene catalysts MACROMOLECULES LEINO, R., Gomez, F. J., Cole, A. P., Waymouth, R. M. 2001; 34 (7): 2072-2082
  • Kinetics of propylene polymerization using bis(2-phenylindenyl)zirconium dichloride/methylaluminoxane JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Lin, S., Tagge, C. D., Waymouth, R. M., Nele, M., Collins, S., PINTO, J. C. 2000; 122 (46): 11275-11285

    View details for DOI 10.1021/ja002003h

    View details for Web of Science ID 000165600300001

  • Two-state models for olefin polymerization using metallocene catalysts. 1. Application to fluxional metallocene catalyst systems MACROMOLECULES Nele, M., Collins, S., Dias, M. L., PINTO, J. C., Lin, S., Waymouth, R. M. 2000; 33 (20): 7249-7260

    View details for DOI 10.1021/ma000401z

    View details for Web of Science ID 000089735800009

  • Ethylene and hydrogen effects in propylene polymerization with 2-arylindenyl zirconocenes JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL Lin, S., Kravchenko, R., Waymouth, R. M. 2000; 158 (1): 423-427
  • Ring-opening reactions of oxabicyclic alkene compounds: enantioselective hydride and ethyl additions catalyzed by group 4 metals JOURNAL OF ORGANIC CHEMISTRY Millward, D. B., Sammis, G., Waymouth, R. M. 2000; 65 (13): 3902-3909

    View details for DOI 10.1021/jo991429f

    View details for Web of Science ID 000087925800003

  • Catalytic carboalumination of olefins with cyclopentadienylamidotitanium dichloride complexes ORGANOMETALLICS Millward, D. B., Cole, A. P., Waymouth, R. M. 2000; 19 (10): 1870-1878
  • Accurate structural control and block formation in the living polymerization of 1,3-dienes by nitroxide-mediated procedures MACROMOLECULES Benoit, D., Harth, E., Fox, P., Waymouth, R. M., Hawker, C. J. 2000; 33 (2): 363-370
  • Ring-opening reactions of oxabicyclic alkene compounds: enantioselective hydride and ethyl additions catalyzed by group 4 metals The Journal of organic chemistry Millward, D. B., Sammis, G., Waymouth, R. M. 2000; 65 (13): 3902-9

    Abstract

    Titanium and zirconium catalysts selectively catalyze either the ethyl or hydride addition to [2.2.1] 4, 5-bis(methoxymethyl)-7-oxabicycloheptene (6); the ring-opened products formed depend on catalyst, temperature, alkylaluminum reagent, and the concentration of alkylaluminum. Bis(neoisomenthylindenyl)zirconium dichloride catalyzes the ethyl addition ring-opening of 6 to produce (1R,2S,3S,6R)-2, 3-bis(methoxymethyl)-6-ethylcyclohex-4-enol (7) in 96% ee. Zirconium catalysts catalyze the ring-opening of [3.2.1] 2, 4-dimethyl-3-(benzyloxy)-8-oxabicyclo-6-octene (7) when ethylmagnesium bromide is used as a reagent. Both hydride and ethyl addition products are obtained at all conditions studied. Bis(neoisomenthylindenyl)zirconium dichloride catalyzes the ethyl addition ring-opening of 7 to produce (1S,2R,3S,4S,7S)-2, 4-dimethyl-3-(benzyloxy)-7-ethyl-5-cyclohexen-1-ol (8) in 48% ee.

    View details for PubMedID 10866606

  • Olefin polymerization with Me4Cp-amido complexes with electron-withdrawing groups JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY Kamigaito, M., Lal, T. K., Waymouth, R. M. 2000; 38: 4649-4660
  • Regioirregular propene insertion in polypropenes synthesized with unbridged bis(2-aryl)indenyl zirconium dichloride catalysts: Implications on activity MACROMOLECULES Lin, S., Waymouth, R. M. 1999; 32 (25): 8283-8290
  • Component relaxation processes within elastomeric polypropylene MACROMOLECULES Carlson, E. D., Fuller, G. G., Waymouth, R. M. 1999; 32 (24): 8100-8106
  • Influence of trialkylaluminum reagents on the propylene polymerization behavior of bridged and unbridged 2-arylindene metallocene polymerization catalysts MACROMOLECULES Petoff, J. L., Myers, C. L., Waymouth, R. M. 1999; 32 (24): 7984-7989
  • Transient birefringence of elastomeric polypropylene subjected to step shear strain MACROMOLECULES Carlson, E. D., Fuller, G. G., Waymouth, R. M. 1999; 32 (24): 8094-8099
  • Synthesis of unbridged bis(2-R-indenyl)zirconocenes containing functional groups and investigations in propylene polymerization ORGANOMETALLICS Witte, P., Lal, T. K., Waymouth, R. M. 1999; 18 (20): 4147-4155
  • Elastomeric polypropylenes from unbridged 2-phenylindene zirconocene catalysts: Temperature dependence of crystallinity and relaxation properties MACROMOLECULES Hu, Y. R., Carlson, E. D., Fuller, G. G., Waymouth, R. M. 1999; 32 (10): 3334-3340
  • Ethylene norbornene copolymerizations with titanium CpA catalysts MACROMOLECULES McKnight, A. L., Waymouth, R. M. 1999; 32 (9): 2816-2825
  • Mixed ligand metallocenes as catalysts for elastomeric polypropylene ORGANOMETALLICS Tagge, C. D., Kravchenko, R. L., Lal, T. K., Waymouth, R. M. 1999; 18 (3): 380-388
  • Metallocene/borate-catalyzed copolymerization of 5-N,N-diisopropylamino-1-pentene with 1-hexene or 4-methyl-1-pentene MACROMOLECULES Stehling, U. M., Stein, K. M., Fischer, D., Waymouth, R. M. 1999; 32 (1): 14-20
  • Steric and electronic effects of R in (2-(4-R-C6H4)indenyl)(2)ZrCl2 catalysts on the synthesis of elastomeric polypropylene JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL Lin, S., Hauptman, E., Lal, T. K., Waymouth, R. M., Quan, R. W., Ernst, A. B. 1998; 136 (1): 23-33
  • Elastomeric polypropylene from unbridged 2-arylindenyl zirconocenes: Modeling polymerization behavior using ansa-metallocene analogues JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Petoff, J. L., Agoston, T., Lal, T. K., Waymouth, R. M. 1998; 120 (44): 11316-11322
  • Group 4 ansa-cyclopentadienyl-amido catalysts for olefin polymerization CHEMICAL REVIEWS McKnight, A. L., Waymouth, R. M. 1998; 98 (7): 2587-2598
  • Elastomeric polypropylenes from unbridged (2-phenylindene)zirconocene catalysts: Thermal characterization and mechanical properties MACROMOLECULES Hu, Y. R., Krejchi, M. T., Shah, C. D., Myers, C. L., Waymouth, R. M. 1998; 31 (20): 6908-6916
  • Rheological and thermal properties of elastomeric polypropylene MACROMOLECULES Carlson, E. D., Krejchi, M. T., Shah, C. D., Terakawa, T., Waymouth, R. M., Fuller, G. G. 1998; 31 (16): 5343-5351
  • Synthesis of poly(olefin) graft copolymers by a combination of metallocene and "living" free radical polymerization techniques MACROMOLECULES Stehling, U. M., Malmstrom, E. E., Waymouth, R. M., Hawker, C. J. 1998; 31 (13): 4396-4398
  • Statistical analysis and simulation of pentad distributions of stereoblock polypropylenes MACROMOLECULES BRUCE, M. D., Waymouth, R. M. 1998; 31 (9): 2707-2715
  • Alternating ethene/propene copolymerization with a metallocene catalyst ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Leclerc, M. K., Waymouth, R. M. 1998; 37 (7): 922-925
  • Metallocene/borate-catalyzed polymerization of amino-functionalized alpha-olefins MACROMOLECULES Stehling, U. M., Stein, K. M., Kesti, M. R., Waymouth, R. M. 1998; 31 (7): 2019-2027
  • Strategies for synthesis of elastomeric polypropylene: Fluxional metallocenes with C-1-symmetry JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Kravchenko, R., Masood, A., Waymouth, R. M., Myers, C. L. 1998; 120 (9): 2039-2046
  • Ethylene-propylene copolymerization with 2-arylindene zirconocenes MACROMOLECULES Kravchenko, R., Waymouth, R. M. 1998; 31 (1): 1-6
  • Group 4 ansa-Cyclopentadienyl-Amido Catalysts for Olefin Polymerization. Chemical reviews McKnight, A. L., Waymouth, R. M. 1998; 98 (7): 2587-2598

    View details for PubMedID 11848972

  • Propylene polymerization with unbridged metallocenes: Ligand effects on the selectivity for elastomeric polypropylene ORGANOMETALLICS Petoff, J. L., BRUCE, M. D., Waymouth, R. M., Masood, A., Lal, T. K., Quan, R. W., Behrend, S. J. 1997; 16 (26): 5909-5916
  • Effect of metal on the stereospecificity of 2-arylindene catalysts for elastomeric polypropylene JOURNAL OF THE AMERICAN CHEMICAL SOCIETY BRUCE, M. D., COATES, G. W., Hauptman, E., Waymouth, R. M., Ziller, J. W. 1997; 119 (46): 11174-11182
  • Propylene polymerization with chiral and achiral unbridged 2-arylindene metallocenes ORGANOMETALLICS Kravchenko, R., Masood, A., Waymouth, R. M. 1997; 16 (16): 3635-3639
  • Selectivity in propylene polymerization with group 4 Cp-amido catalysts ORGANOMETALLICS McKnight, A. L., Masood, M. A., Waymouth, R. M., Straus, D. A. 1997; 16 (13): 2879-2885
  • The effect of ligand structure on the polymerization behavior of unbridged metallocenes Petoff, J. L., BRUCE, M. D., Waymouth, R. M., Masood, A. AMER CHEMICAL SOC. 1997: 156-INOR
  • Zirconocene-mediated cyclization of 2-bromo alpha,omega-dienes ORGANOMETALLICS Millward, D. B., Waymouth, R. M. 1997; 16 (6): 1153-1158
  • Homo-, co- and terpolymerization of 1,5-hexadiene using a methylalumoxane activated mono-Cp-amido-complex POLYMER BULLETIN Sernetz, F. G., Mulhaupt, R., Waymouth, R. M. 1997; 38 (2): 141-148
  • Pd2+-catalyzed cyclocopolymerization of 1,5-hexadiene and CO: Regioselectivity of olefin insertion MACROMOLECULES BORKOWSKY, S. L., Waymouth, R. M. 1996; 29 (20): 6377-6382
  • Effect of metal in the production of elastomeric polypropylene BRUCE, M. D., COATES, G. W., Waymouth, R. M. AMER CHEMICAL SOC. 1996: 88-INOR
  • Temporal chirality: Dynamic stereocontrol in the polymerization of propylene Coates, G., Hauptman, E., Bruce, M., Waymouth, R. AMER CHEMICAL SOC. 1996: 234-POLY
  • Influence of polymerization conditions on the copolymerization of styrene with ethylene using Me(2)Si(Me(4)Cp)(N-tert-butyl)TiCl2 methylaluminoxane Ziegler-Natta catalysts MACROMOLECULAR CHEMISTRY AND PHYSICS Sernetz, F. G., Mulhaupt, R., Waymouth, R. M. 1996; 197 (3): 1071-1083
  • Polymer synthesis and stereochemistry with transition metal catalysts CHEMICAL SYNTHESIS Waymouth, R., COATES, G. W., Ciardelli, F., Carlini, C., Altomare, A. 1996; 320: 453-473
  • METALLOCENE CATALYSTS FOR STEREOSELECTIVE POLYMERIZATION Coates, G., MOGSTAD, A. L., Hauptman, E., Bruce, M., KREJCHE, M., Kravchenko, R., Waymouth, R. AMER CHEMICAL SOC. 1995: 167-ORGN
  • STEREOSPECIFIC OLEFIN POLYMERIZATION WITH CHIRAL METALLOCENE CATALYSTS ANGEWANDTE CHEMIE-INTERNATIONAL EDITION IN ENGLISH Brintzinger, H. H., Fischer, D., Mulhaupt, R., Rieger, B., Waymouth, R. M. 1995; 34 (11): 1143-1170
  • OSCILLATING CATALYSTS FOR PROPYLENE POLYMERIZATION Coates, G., MOGSTAD, A. L., Hauptman, E., Bruce, M., Waymouth, R. AMER CHEMICAL SOC. 1995: 191-POLY
  • ENVIRONMENTALLY BENIGN POLYMER SYNTHESIS - POLYSILANE PHOTORESISTS Hsiao, Y. L., Waymouth, R. M., Beach, J. V., Loy, D. A. AMER CHEMICAL SOC. 1995: 127-ORGN
  • ENVIRONMENTALLY FRIENDLY POLYSILANES - AN ALTERNATIVE ROUTE TO POLYSILANE PHOTORESISTS Beach, J. V., Loy, D. A., Hsiao, Y. L., Waymouth, R. M. AMER CHEMICAL SOC. 1995: 121-PMSE
  • CONSTRUCTING CYCLICS FROM SIMPLE OLEFINS CHEMTECH WAYMOUTH, R. H., Knight, K. S. 1995; 25 (4): 15-21
  • THERMAL AND STRUCTURAL CHARACTERIZATION OF POLY(METHYLENE-1,3-CYCLOPENTANE) SAMPLES OF DIFFERENT MICROSTRUCTURES MACROMOLECULES DEBALLESTEROS, O. R., Venditto, V., Auriemma, F., Guerra, G., RESCONI, L., Waymouth, R., MOGSTAD, A. L. 1995; 28 (7): 2383-2388
  • OSCILLATING STEREOCONTROL - A STRATEGY FOR THE SYNTHESIS OF THERMOPLASTIC ELASTOMERIC POLYPROPYLENE SCIENCE COATES, G. W., Waymouth, R. M. 1995; 267 (5195): 217-219

    Abstract

    A strategy has been developed for the synthesis of thermoplastic elastomeric polypropylene based on the catalytic activity of the unbridged metallocene bis(2-phenylindenyl)zirconium dichloride [(2-PhInd)(2)ZrCl(2)]. This catalyst was designed to isomerize between achiral and chiral coordination geometries during the polymerization reaction to produce atactic-isotactic stereoblock polymers. The metallocene precursor (2-PhInd)(2)ZrCl(2) in the presence of methylaluminoxane polymerizes propylene to yield rubbery polypropylene. The isotacticity of the polymer, described by the isotactic pentad content, increases with increasing propylene pressure and decreasing polymerization temperature to produce polypropylenes with an isotactic pentad content ranging from 6.3 to 28.1 percent.

    View details for Web of Science ID A1995QB15300028

    View details for PubMedID 17791342

  • Environmentally friendly polysilane photoresists MICROELECTRONICS TECHNOLOGY Beach, J. V., Loy, D. A., Hsiao, Y. L., Waymouth, R. M. 1995; 614: 355-366
  • FREE-RADICAL HYDROSILYLATION OF POLY(PHENYLSILANE) - SYNTHESIS OF FUNCTIONAL POLYSILANES JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Hsiao, Y. L., Waymouth, R. M. 1994; 116 (21): 9779-9780
  • A NEW ROUTE TO FUNCTIONALIZED POLY(PHENYLSILANES) Hsiao, Y. L., Waymouth, R. M. AMER CHEMICAL SOC. 1994: 52-INOR
  • SYNTHESIS OF CONTROLLED POLYMER STRUCTURES USING TRANSITION-METAL CATALYSTS Coates, G., MOGSTAD, A. L., Bruce, M., Stein, K., BORKOWSKY, S., Waymouth, R. AMER CHEMICAL SOC. 1994: 125-ORGN
  • SYNTHESIS OF FUNCTIONALIZED POLYOLEFINS USING GROUP-4 METALLOCENE CATALYSTS Coates, G., Stein, K., Fischer, D., Waymouth, R. AMER CHEMICAL SOC. 1994: 271-INOR
  • MECHANISM AND STEREOCHEMISTRY OF THE ZIRCONOCENE-CATALYZED CYCLOMAGNESIATION OF DIENES JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Knight, K. S., Wang, D., Waymouth, R. M., Ziller, J. 1994; 116 (5): 1845-1854
  • SUBSTITUENT EFFECTS ON UV ABSORPTION OF SIGMA-CONJUGATED POLYSILANES INORGANIC AND ORGANOMETALLIC POLYMERS II Hsiao, Y. L., BANOVETZ, J. P., Waymouth, R. M. 1994; 572: 55-63
  • FUNCTIONALIZATION OF POLY(PHENYL)SILANE BANOVETZ, J. P., Hsiao, Y. L., Waymouth, R. M. AMER CHEMICAL SOC. 1993: 161-POLY
  • SELECTIVE FREE-RADICAL HALOGENATION OF POLYPHENYLSILANE JOURNAL OF THE AMERICAN CHEMICAL SOCIETY BANOVETZ, J. P., Hsiao, Y. L., Waymouth, R. M. 1993; 115 (6): 2540-2541
  • MODEL CATALYTIC SITES FOR OLEFIN POLYMERIZATION AND DIASTEREOSELECTIVITY IN THE CYCLOPOLYMERIZATION OF 1,5-HEXADIENE MACROMOLECULES Cavallo, L., Guerra, G., Corradini, P., RESCONI, L., Waymouth, R. M. 1993; 26 (2): 260-267
  • CRYSTAL-STRUCTURES OF (ETA-5-C5ME5)(ETA-5-2,4-C7H11)CR AND (ETA-5-C5ME5)-(ETA-5-2,4-C7H11)CRCO - AN EXAMPLE OF S 2,4-DIMETHYLPENTADIENYL LIGAND GEOMETRY INORGANICA CHIMICA ACTA BOVINO, S. C., COATES, G. W., BANOVETZ, J. P., Waymouth, R. M., Straus, D. A., Ziller, J. W. 1993; 203 (2): 179-183
  • ENANTIOSELECTIVE CYCLOPOLYMERIZATION OF 1,5-HEXADIENE CATALYZED BY CHIRAL ZIRCONOCENES - A NOVEL STRATEGY FOR THE SYNTHESIS OF OPTICALLY-ACTIVE POLYMERS WITH CHIRALITY IN THE MAIN CHAIN JOURNAL OF THE AMERICAN CHEMICAL SOCIETY COATES, G. W., Waymouth, R. M. 1993; 115 (1): 91-98
  • STEREOSELECTIVE CYCLOMAGNESIATION OF 1,6-HEPTADIENES CATALYZED BY ZIRCONOCENES - EFFECTS OF SUBSTITUENTS, SOLVENT AND MAGNESIUM REAGENTS TETRAHEDRON LETTERS WISCHMEYER, U., Knight, K. S., Waymouth, R. M. 1992; 33 (50): 7735-7738
  • CHIRAL POLYMERS VIA CYCLOPOLYMERIZATION JOURNAL OF MOLECULAR CATALYSIS COATES, G. W., Waymouth, R. M. 1992; 76 (1-3): 189-194
  • FREE-RADICAL HALOGENATION OF POLYPHENYLSILANE BANOVETZ, J. P., Hsiao, Y. L., Waymouth, R. M. AMER CHEMICAL SOC. 1992: 382-ORGN
  • FUNCTIONALIZATION OF POLY(PHENYLSILANE) BANOVETZ, J. P., Hsiao, Y. L., Waymouth, R. M. AMER CHEMICAL SOC. 1992: 118-INOR
  • GROUP-4 METALLOCENE OLEFIN HYDROSILYLATION CATALYSTS ORGANOMETALLICS Kesti, M. R., Waymouth, R. M. 1992; 11 (3): 1095-1103
  • STEREOSPECIFIC CYCLOPOLYMERIZATION WITH GROUP-4 METALLOCENES JOURNAL OF MACROMOLECULAR SCIENCE-CHEMISTRY RESCONI, L., COATES, G. W., MOGSTAD, A., Waymouth, R. M. 1991; A28 (11-12): 1225-1234