Bio


Designing and synthesizing exotic small and giant molecules for custom properties, Assistant Professor Yan Xia works at the interface of synthetic chemistry and materials science. His research uses a combination of catalysis, organic and polymer chemistry, and a range of advanced characterizations to create, control, and study novel (macro)molecular structures and organic materials with tailored conformations, nanostructures, properties, and functions.

Research in the Xia Group combines vigorous function-driven syntheses, rational molecular design, and in-depth understanding of (macro)molecular reactivity, property, and function. Powerful synthetic methods are the enabling force behind their development of novel organic materials. They have developed various types of chemistry to generate diverse molecular ladder materials with high microporosity, antiaromaticity, or responsive behavior; controlled polymers with defined microstructures and functionalities; and dynamic polymer networks. These new molecular materials have interesting nanostructures, optoelectronic structures, mechanical properties, stimuli-responses, and assembly behaviors, for potential applications spanning separation, electronics, and health care.

Yan Xia studied chemistry at Peking University (B.S. 2002) and McMaster University (M.S. 2005), before his doctoral research on the synthesis and study of cyclic and bottlebrush polymers at California Institute of Technology with Profs. Grubbs and Kornfield (Ph.D. 2010). Following his PhD, he spent one and a half years at Dow Chemical core R&D developing materials for electronic applications, and then performed post-doctoral research on polymer-protein conjugation and assembly at Massachusetts Institute of Technology with Prof. Olsen. He joined the chemistry faculty at Stanford in the summer of 2013 to continue his longstanding interest in developing organic materials by intimately integrating synthetic chemistry with materials science.

Academic Appointments


Honors & Awards


  • Cottrell Scholar Award, Research Corporation for Science Advancement (2017)
  • Thieme Chemistry Journals Award, Thieme Chemistry (2017)
  • CAREER Award, National Science Foundation (2016)
  • 3M Non-Tenured Faculty Award, 3M (2016)
  • Terman Fellowship, Stanford (2014-16)
  • Army Research Office Young Investigator Award, U.S. Army Research Laboratory, Army Research Office (2015)

Professional Education


  • PhD, California Institute of Technology, Chemistry (2010)
  • MS, McMaster University, Chemistry (2005)
  • BS, Peking University, Chemistry (2002)

Current Research and Scholarly Interests


Organic Chemistry, Polymer Chemistry, Organic Optoelectronic Materials, Microporous Polymers, Responsive Polymers, Self-Assembly

2017-18 Courses


Stanford Advisees


All Publications


  • Streamlined Synthesis of Polycyclic Conjugated Hydrocarbons Containing Cyclobutadienoids via C-H Activated Annulation and Aromatization. Journal of the American Chemical Society Jin, Z., Teo, Y. C., Zulaybar, N. G., Smith, M. D., Xia, Y. 2017; 139 (5): 1806-1809

    Abstract

    The juxtaposition of fused cyclobutadienoid (CBD) with benzenoid creates intriguing alternating antiaromatic and aromatic conjugation. Synthetic accessibility of such molecules, however, has been challenging and limited in scope. We report a modular and streamlined synthetic strategy to access a large variety of polycyclic conjugated hydrocarbons with fused CBD. Synthesis was achieved through efficient palladium-catalyzed C-H activated annulation between abundant aryl bromides and oxanorbornenes, followed by aromatization under acidic conditions. The influence of four-membered ring was examined using spectroscopy, crystallography, and computation. This strategy will facilitate exploration on the chemical, structural, and electronic properties of such conjugated systems containing CBD.

    View details for DOI 10.1021/jacs.6b12888

    View details for PubMedID 28125224

  • Mechanochemical unzipping of insulating polyladderene to semiconducting polyacetylene Science Chen, Z., Mercer, J. A., Zhu, X., Romaniuk, J. A., Pfattner, R., Cegelski, L., Martinez, T. J., Burns, N. Z., Xia, Y. 2017; 357 (6350): 475-479
  • Importance of Macromonomer Quality in the Ring-Opening Metathesis Polymerization of Macromonomers MACROMOLECULES Teo, Y. C., Xia, Y. 2015; 48 (16): 5656-5662
  • Living Alternating Ring-Opening Metathesis Polymerization Based on Single Monomer Additions JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Elling, B. R., Xia, Y. 2015; 137 (31): 9922-9926

    Abstract

    By judiciously modulating the ring strain and sterics, we developed a class of disubstituted cyclopropenes that selectively underwent single monomer addition in ring-opening metathesis but readily underwent alternating ring-opening metathesis polymerization with low-strain cyclic olefins in a living fashion. The substituents on cyclopropenes effectively inhibited homoaddition and prevented secondary metathesis on the polymer backbone. The resulting polymers had controllable molecular weights and end groups, very low dispersities, and high regularity in microstructure under optimized conditions. (1)H and (13)C NMR spectroscopy and MALDI-TOF MS showed a rigorously alternating sequence. Interestingly, disubstituted cyclopropenes were found to present zero-order kinetics, indicating their rapid single addition and the rate-determining ring opening of the low-strain olefin.

    View details for DOI 10.1021/jacs.5b05497

    View details for Web of Science ID 000359613300027

    View details for PubMedID 26182144

  • Efficient Synthesis of Rigid Ladder Polymers via Palladium Catalyzed Annulation. Journal of the American Chemical Society Liu, S., Jin, Z., Teo, Y. C., Xia, Y. 2014; 136 (50): 17434-17437

    Abstract

    We report a new method to synthesize rigid ladder polymers using efficient palladium catalyzed annulation reactions with low catalyst loading (1 mol %). Rigid ladder polymers with benzocyclobutene backbone linkages can be synthesized from copolymerization of readily accessible aryl dibromides and norbornadiene or polymerization of AB type monomers bearing norbornene and aryl bromide or triflate moieties. High molecular weight (10-40 kDa) rigid ladder polymers can be obtained with complete monomer conversions. Diverse monomers also gave different, fixed ladder polymer conformations. The ladder polymers exhibited excellent thermal stability, high carbonization yield, and large intrinsic porosity.

    View details for DOI 10.1021/ja5110415

    View details for PubMedID 25423254

  • Ring-opening metathesis polymerization of 1,2-disubstituted cyclopropenes CHEMICAL COMMUNICATIONS Elling, B. R., Su, J. K., Xia, Y. 2016; 52 (58): 9097-9100

    Abstract

    The ring-opening metathesis polymerization (ROMP) of 1,2-disubstituted cyclopropenes (CPs) has been explored for the first time using Grubbs 3rd generation catalyst. A range of 1,2-CPs yielded polymers with controllable MWs and low dispersitities, and allowed the synthesis of block copolymers, absent from secondary metathesis. However, there existed a competing intramolecular termination pathway for these monomers, limiting the timescale for their ROMP to stay living.

    View details for DOI 10.1039/c6cc00466k

    View details for Web of Science ID 000379431000029

    View details for PubMedID 26947899

  • Synthesis and Direct Imaging of Ultrahigh Molecular Weight Cyclic Brush Polymers ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Xia, Y., Boydston, A. J., Grubbs, R. H. 2011; 50 (26): 5882-5885

    View details for DOI 10.1002/anie.201101860

    View details for Web of Science ID 000292001700017

    View details for PubMedID 21591042

  • Efficient Synthesis of Narrowly Dispersed Brush Copolymers and Study of Their Assemblies: The Importance of Side-Chain Arrangement JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Xia, Y., Olsen, B. D., Kornfield, J. A., Grubbs, R. H. 2009; 131 (51): 18525-18532

    Abstract

    Efficient, one-pot preparation of synthetically challenging, high molecular weight (MW), narrowly dispersed brush block copolymers and random copolymers in high conversions was achieved by ring-opening metathesis (co)polymerization (ROMP) of various macromonomers (MMs) using the highly active, fast-initiating ruthenium olefin metathesis catalyst (H(2)IMes)(pyr)(2)(Cl)(2)RuCHPh. A series of random and block copolymers were prepared from a pair of MMs containing polylactide (PLA) and poly(n-butyl acrylate) (PnBA) side chains at similar MWs. Their self-assembly in the melt state was studied by small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). In brush random copolymers containing approximately equal volume fractions of PLA and PnBA, the side chains segregate into lamellae with domain spacing of 14 nm as measured by SAXS, which was in good agreement with the lamellar thickness measured by AFM. The domain spacings and order-disorder transition temperatures of brush random copolymers were insensitive to the backbone length. In contrast, brush block copolymers containing approximately equal volume fractions of these MMs self-assembled into highly ordered lamellae with domain spacing over 100 nm. Their assemblies suggested that the brush block copolymer backbone adopted an extended conformation in the ordered state.

    View details for DOI 10.1021/ja908379q

    View details for Web of Science ID 000273615800066

    View details for PubMedID 19947607

  • Ring-Expansion Metathesis Polymerization: Catalyst-Dependent Polymerization Profiles JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Xia, Y., Boydston, A. J., Yao, Y., Kornfield, J. A., Gorodetskaya, I. A., Spiess, H. W., Grubbs, R. H. 2009; 131 (7): 2670-2677

    Abstract

    Ring-expansion metathesis polymerization (REMP) mediated by recently developed cyclic Ru catalysts has been studied in detail with a focus on the polymer products obtained under varied reaction conditions and catalyst architectures. Depending upon the nature of the catalyst structure, two distinct molecular weight evolutions were observed. Polymerization conducted with catalysts bearing six-carbon tethers displayed rapid polymer molecular weight growth which reached a maximum value at ca. 70% monomer conversion, resembling a chain-growth polymerization mechanism. In contrast, five-carbon-tethered catalysts led to molecular weight growth that resembled a step-growth mechanism with a steep increase occurring only after 95% monomer conversion. The underlying reason for these mechanistic differences appeared to be ready release of five-carbon-tethered catalysts from growing polymer rings, which competed significantly with propagation. Owing to reversible chain transfer and the lack of end groups in REMP, the final molecular weights of cyclic polymers was controlled by thermodynamic equilibria. Large ring sizes in the range of 60-120 kDa were observed at equilibrium for polycyclooctene and polycyclododecatriene, which were found to be independent of catalyst structure and initial monomer/catalyst ratio. While six-carbon-tethered catalysts were slowly incorporated into the formed cyclic polymer, the incorporation of five-carbon-tethered catalysts was minimal, as revealed by ICP-MS. Further polymer analysis was conducted using melt-state magic-angle spinning (13)C NMR spectroscopy of both linear and cyclic polymers, which revealed little or no chain ends for the latter topology.

    View details for DOI 10.1021/ja808296a

    View details for Web of Science ID 000263576100055

    View details for PubMedID 19199611

  • Well-defined liquid crystal gels from telechelic polymers JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Xia, Y., Verduzco, R., Grubbs, R. H., Kornfield, J. A. 2008; 130 (5): 1735-1740

    Abstract

    Well-defined liquid crystal networks with controlled molecular weight between cross-links and cross-link functionality were prepared by "click" cross-linking of telechelic polymers produced by ring-opening metathesis polymerization (ROMP). The networks readily swell in a small molecule liquid crystal, 5CB, to form LC gels with high swelling ratios. These gels exhibit fast, reversible, and low-threshold optic switching under applied electric fields when they are unconstrained between electrodes. For a given electric field, the LC gels prepared from shorter telechelic polymers showed a reduced degree of switching than their counterparts made from longer polymer strands. The reported approach provides control over important parameters for LC networks, such as the length of the network strands between cross-links, cross-linker functionality, and mesogen density. Therefore, it allows a detailed study of relationships between molecular structure and macroscopic properties of these scientifically and technologically interesting networks.

    View details for DOI 10.1021/ja077192j

    View details for Web of Science ID 000253100100047

    View details for PubMedID 18197667