Lukas Michalek

All Publications

• Localized Thermomechanical Measurements of Polymers and Blends with AFM-IR. Small (Weinheim an der Bergstrasse, Germany) Lim, C. Y., Bao, Z., Michalek, L. 2026: e14518

  Abstract

  Understanding the thermomechanical behavior of heterogeneous polymer systems is crucial for material design. Herein, we introduce a novel technique that couples chemistry-selective infrared (IR) heating with atomic force microscopy (AFM) nanomechanical measurements. We demonstrate that surface heating of the sample on the AFM-IR can be varied with the IR repetition rate, evidenced by melting poly(ethylene glycol) (PEG) films over a range of molecular weight-dependent melting points. Chemical-selective heating was demonstrated, where heating is dependent on the characteristic IR absorption bands of the material. Coupling of IR laser heating with nanomechanical measurements enables the qualitative detection of its glass transition temperature in thickness-confined semi-crystalline poly(lactic acid) (PLA) films, where an ultra-thin PLA film demonstrated a decrease in modulus to half its initial value with a significantly lower IR repetition rate relative to the IR repetition rate required to induce the same change in a thick PLA film. We further apply this technique to a polymer blend of PLA and uncrosslinked nitrile butadiene rubber to demonstrate phase-specific thermal characterization. This technique minimizes thermal drift, allows for rapid heating with concurrent AFM measurements and circumvents bulk material changes, paving a possible alternative avenue for the probing of thermomechanical properties of heterogenous films.

  View details for DOI 10.1002/smll.202514518

  View details for PubMedID 41773455

• A guide for nanomechanical characterization of soft matter via AFM: From mode selection to data reporting. STAR protocols Kim, E., Ramos Figueroa, A. L., Schrock, M., Zhang, E., Newcomb, C. J., Bao, Z., Michalek, L. 2025; 6 (2): 103809

  Abstract

  Atomic force microscopy (AFM) enables high-resolution mechanical characterization of soft materials at the nanoscale. It offers unique advantages over conventional mechanical testing methods by providing spatially resolved properties, requiring minimal sample preparation, and allowing measurements under controlled environmental conditions. This comprehensive guide provides a practical framework for conducting reproducible nanomechanical measurements on soft matter using AFM. Readers will learn how to select appropriate AFM modes, choose and calibrate suitable cantilevers, prepare samples, and optimize measurement parameters for soft materials. Four operational AFM modes are described: intermittent contact mode, nanomechanical imaging, force modulation, and force spectroscopy. We detail their principles, mechanisms, and trade-offs while offering practical advice for experiment execution, data analysis, and result reporting. This protocol seeks to guide researchers to execute consistent and comparable AFM measurements, bridge the gap between theoretical knowledge and practical implementation, and address key challenges in standardization and reproducibility within the field of soft matter nano-mechanics.

  View details for DOI 10.1016/j.xpro.2025.103809

  View details for PubMedID 40449004

• A monolithic fabrication platform for intrinsically stretchable polymer transistors and complementary circuits DEVICE Yuan, Y., Zhao, C., Ronchini, M., Nishio, Y., Zhong, D., Wu, C., Kweon, H., Sun, Z., Mow, R. K., Shi, Y., Michalek, L., Wu, H., Liu, Q., Wang, W., Yao, Y., Yin, Z., Zhao, J., He, Z., Chen, K., Wu, R., Shi, J., Pei, J., Bao, Z. 2026; 4 (8)

  View details for DOI 10.1016/j.device.2026.101204

  View details for Web of Science ID 001856554100001

• Solvent-Mediated Diffusion Enables Directed Functionalization of Polymer Semiconductor Interfaces. ACS applied materials & interfaces Schrock, M., Michalek, L., Chen, Q. G., Liu, Q., Mow, R. K., Shi, Y., Bao, Z. 2026

  Abstract

  The increasing interest in the development of intrinsically stretchable electronic devices based on polymer semiconductors (PSCs) necessitates a comprehensive understanding of the interfacial chemistry of these PSC films, alongside facile processing methods to modify these properties, which dictate layer compatibility. Solvent-mediated functionalization provides a scalable, controllable, and tunable method to target and modulate several key interfacial properties. Herein, we aim to understand the influence of solvent exposure on a blended polymer film. This is achieved through small molecule modification of a poly-thieno[3,2-b]thiophene-diketopyrrolopyrrole (DPPTT) and low molecular weight polybutadiene (BA)-blended elastomer film. We investigated solvent-mediated film functionalization on blended films by incorporating 1H,1H,2H,2H-perfluorodecanethiol (PFDT), as the highly fluorinated small molecule provided excellent measurement contrast throughout several characterization techniques. By comparing solvent environments that differentially swell the blended polymer films, we show programming of PFDT incorporation from uniform, through-thickness functionalization to surface-enriched gradients. Quartz crystal microbalance with dissipation monitoring (QCM-D) measurements and further corroborated with X-ray photoelectron spectroscopy (XPS) depth profiles quantified the estimated apparent mass uptake of PFDT. In a non-swelling/compacting solvent environment, QCM-D reflected a diffusion-governed uptake of PFDT with a distinct thickness-dependent concentration gradient. In contrast, swelling films with methoxyperfluorobutane (MPFB) opened diffusion pathways that facilitated PFDT penetration throughout the entire polymer network and resulted in more uniform functionalization across the entire film thickness. Collectively, these results establish a broader understanding of solvent-mediated film functionalization and further the understanding of molecular diffusion through PSC film systems.

  View details for DOI 10.1021/acsami.6c07306

  View details for PubMedID 42571656

• Biofunctionalized polymer semiconductors toward soft and stretchable transistor-based biosensors. Science advances Zhao, C., Liu, Q., Chang, J. Y., Patil, A., Michalek, L., Wu, Y., Yuan, Y., Mow, R. K., Shi, Y., Yao, Y., Hsu, K. J., Zheng, Y., Bao, Z. 2026; 12 (23): eaec2641

  Abstract

  Organic materials with tunable chemical and mechanical properties are ideal for interfacing with skin and tissue in biomedical applications. While polymer semiconductors (PSCs) have advanced toward skin-like mechanical performance, the limited capacity for biofunctionalization has restricted their biosensing applications. In this study, we introduce a direct biofunctionalization strategy for PSCs based on thiol-ene chemistry. We selectively grafted thiolated biomolecules (e.g., aptamers) onto elastomeric domains within an interconnected semiconductor/elastomer network. This approach enables high-resolution patterning down to 10 micrometers while preserving the electronic performance of PSCs. Leveraging this platform, we designed and fabricated skin-like electrolyte-gated organic field-effect transistors with biofunctionalized channels. These soft and stretchable devices exhibit stable operation in physiological buffers for more than 50 days and maintain performance under up to 50% strain. When functionalized with cortisol-binding aptamers, the sensors achieved sensitive detection across physiologically relevant concentrations, down to the picomolar range. This work establishes a foundation for integrating stretchable and biofunctional PSCs into skin-like wearable devices.

  View details for DOI 10.1126/sciadv.aec2641

  View details for PubMedID 42247494

• Solution-state nanoconfined aggregation and microstructure evolution in blends of conjugated polymers and elastomers. Proceedings of the National Academy of Sciences of the United States of America Peña-Alcántara, A. E., Ghasemi, M., Cheng, C., Chaney, T. P., Coffey, A. H., Ponte, E., Ji, X., Michalek, L., Wu, Y., Schrock, M., Ngaruka, G., Gala, M. L., Zhu, C., Toney, M. F., Salleo, A., Gomez, E. D., Bao, Z. 2026; 123 (18): e2516186123

  Abstract

  Emerging wearable health monitoring technologies require conformable and stretchable devices. Polymer semiconductors composed of π-conjugated polymer aggregates in an elastomeric matrix are remarkable in their ability to provide both high stretchability and enhanced charge transport. Understanding their film formation process is critical in improving charge transport, imparting added functionalities, and advancing large-scale production of high-performing polymer electronic devices. Here, using a poly-thieno[3,2-b]thiophene-diketopyrrolopyrrole (DPPTT): polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) blend as a model system, electron tomography of the blend reveals the presence of bundles of conjugated polymer nanofibers spanning the thickness of the films. High-resolution cryogenic electron microscopy (cryo-EM) of solution and thin films reveals that the nanoconfined DPPTT nanofibers in blends are composed of the aligned DPPTT 1D aggregates present in solution. In contrast, neat DPPTT solutions and thin films contain irregular crystalline domains with random orientations. In situ grazing incidence wide-angle X-ray scattering (GIWAXS) studies reveal that DPPTT crystallization commences earlier in blends compared to neat films. Combining observations from both in situ ultraviolet-visible spectroscopy, in situ GIWAXS and cryo-EM reveal that 1D aggregates in blend solution bundle and align into interconnected larger fibers that are nanoconfined in the SEBS matrix. This morphology is desirable for efficient charge transport and good mechanical strength. In contrast, neat DPPTT films contain randomly oriented smaller aggregates with an increased fraction of disordered domains. Overall, our work provides critical insights on the impact of solution composition and processing conditions on thin film morphology for achieving multifunctional high-performing electronic polymer composites.

  View details for DOI 10.1073/pnas.2516186123

  View details for PubMedID 42030140

• Intrinsically stretchable complementary circuits based on direct photo-patternable polymer semiconductors NATURE ELECTRONICS Liu, Q., Zheng, Y., Wu, H., Michalek, L., Ronchini, M., Mow, R. K., Wang, W., Park, H., Ji, X., Yu, Z., Yao, Z., Nishio, Y., Zhao, C., Pei, J., Bao, Z. 2026

  View details for DOI 10.1038/s41928-026-01599-z

  View details for Web of Science ID 001740770400001

• Photolyzable Polymer Brushes: Subtractive 3D Structuring of Surfaces Using Water and Light. Angewandte Chemie (International ed. in English) Kalmer, H., Sbordone, F., Do, P. T., Mundsinger, K., Kayas, H., Jones, R. T., Mendhi, J., Dargaville, T. R., Harkin, D. G., Michalek, L., Nelson, A., Frisch, H. 2026: e2790800

  Abstract

  Polymer brushes are a key technology for designing surfaces, with applications in biomedicine alone including biosensing, cell culture, regenerative medicine, and antibacterial coatings. The structuring of polymer brushes has the potential to precisely tailor interfaces for specific application requirements. However, complex fabrication processes can limit the applications of polymer brushes. Herein, a subtractive patterning process is reported, which decouples initial fabrication from the structuring process. Using radical ring-opening polymerization of cyclic monomers with photocleavable cyclobutane rings, photodegradable targets are directly embedded into the polymer brush main chains. After the initial fabrication, these brushes can be readily degraded with light, triggering photocleavage of the cyclobutane units. This enables continuous brush degradation of over 50% of brush height for topographical patterning without affecting brush properties such as hydrophilicity and adhesion force. The inherent photodegradability of the polymer brush eliminates the need for additional chemicals or catalysts and can be carried out using nothing but water and light at ambient temperature.

  View details for DOI 10.1002/anie.2790800

  View details for PubMedID 41972777

• Ultrasensitive soft vibration sensors based on atomically thin metal dichalcogenide ribbon networks. Science advances Xu, C., Li, X., Michalek, L. F., Park, J., Kim, E., Zhang, Z., Unocic, R. R., Zhao, E. T., Hsu, W. C., Shi, B., Wu, S., Yang, Y., Harutyunyan, A. R., Bao, Z. 2026; 12 (12): eaeb6733

  Abstract

  The rapid progress of artificial intelligence (AI) and the internet of things (IoT) has driven growing demand for high-performance, skin-compatible vibration sensors capable of capturing subtle physiological and environmental signals. Low-dimensional materials offer unique advantages in sensitivity and flexibility, yet challenges remain in achieving high strain responsiveness, mechanical robustness, and large-area uniformity. Here, we report an ultrasensitive, low-profile, and stretchable vibration sensor based on large-area single-layer molybdenum disulfide (MoS2) ribbon networks (SLRNs) grown via a vapor-liquid-solid mechanism. Embedding SLRNs within a thermoplastic elastomer [styrene-ethylene-butylene-styrene (SEBS)] yields record-high sensitivity among MoS2-based sensors, with gauge factors up to 5300 at <1.6% strain. This response arises from nanocrack-mediated electron transport induced by the thermal expansion mismatch between MoS2 and SEBS. The ~6-micrometer-thick sensors detect vibrations and acoustic signals over a wide frequency range (>500 hertz), enabling deconvolution of complex stimuli. This work establishes a path toward ultrathin, ultrasensitive wearable sensors for health care and robotic applications.

  View details for DOI 10.1126/sciadv.aeb6733

  View details for PubMedID 41861005

• Field-Responsive Dynamic Monolayer Regulated Interphase for Enhanced Lithium Metal Batteries. Journal of the American Chemical Society Zhang, E., Holoubek, J., Lyu, H., Li, Y., Florian, J., Shuchi, S. B., Lee, J. K., Michalek, L., Chen, T., Chen, Z., Choi, I. R., Guo, X., Mondonico, L., Cui, Y., Bao, Z. 2026

  Abstract

  Lithium metal batteries offer high energy density but suffer from persistent interphase instability, where continuous corrosion, solid electrolyte interphase (SEI) growth and poor lithium deposition morphology remain key barriers to long cycle and calendar life. Here, we introduce a novel concept of dynamic monolayers on Li metal anodes, consisting of electric field-responsive molecules that assemble into packed, structured layers at the lithium interphase under an applied voltage. We employed electrochemical quartz crystal microbalance with dissipation monitoring for in situ verification of the field responsiveness and packing behavior of these molecules. Dynamic monolayers with stronger packing are found to promote more inorganic-rich SEI and chunkier lithium growth, as directly observed by cryogenic X-ray photoelectron spectroscopy and operando optical microscopy. Together, these interfacial improvements translate into enhanced Coulombic Efficiency, reduced overpotential, and improved long-term cycling stability across Li||Cu, Li||Li, ultrathin lithium (20 mum) and anode-free NMC811 configurations. Dynamic monolayers potentially provide a broadly applicable approach for tackling interfacial challenges across a range of alkali metal battery systems.

  View details for DOI 10.1021/jacs.5c19365

  View details for PubMedID 41649298

• Temperature-Controlled Phase Separation Behavior of Conjugated Polymer:Elastomer Blends of PffBT4T-2OD and SEBS ACS APPLIED ELECTRONIC MATERIALS Pena-Alcantara, A. E., Nikzad, S., Ngaruka, G., Michalek, L., Bao, Z. 2026

  View details for DOI 10.1021/acsaelm.5c01823

  View details for Web of Science ID 001683982800001

• Stabilizing All-Solid-State Li-S Batteries by a Polysulfide-Repelling and Anode-Protecting Self-Segregated Trilayer Polymer Electrolyte. Journal of the American Chemical Society Lyu, H., Gao, X., Michalek, L., Chen, T., Yu, W., Lim, C. Y., Florian, J., Mondonico, L., Zhang, W., Sarkar, S., Zhang, P., Shi, Y., Lin, K., Liao, S., Zheng, X., Qin, J., Cui, Y., Bao, Z. 2026

  Abstract

  Rational management of lithium polysulfide (LiPS) transport is essential for stable, high-energy-density Li-S batteries. We introduce a freestanding, self-segregated trilayer polymer electrolyte (TLE) that forms two layers of nanometer-thin, ion-selective coatings at the cathode and anode interfaces by autonomous phase separation of two immiscible polymers while preserving a highly conductive bulk matrix. In Li-S cells, these coatings simultaneously repel dissolved LiPS at the sulfur cathode and stabilize lithium plating and stripping at the Li metal anode without sacrificing ion transport. Operando optical cell monitoring and theoretical modeling reveal that the dual-functional coatings are responsible for stable Li metal anode operation and effective shuttle suppression. The TLE enables an initial discharge capacity of 1369 mAh g-1 (81.7% of theoretical) and maintains a stable capacity over 50 cycles at 0.2C. Fabricated by a single-step casting process, this scalable electrolyte membrane offers a practical route to durable, all-solid-state Li-S batteries.

  View details for DOI 10.1021/jacs.5c18042

  View details for PubMedID 41622643

• Polydopamine-Mediated Grafting of Cationic Polymer Brushes for Adsorption of Fluorinated Compounds. Chemistry (Weinheim an der Bergstrasse, Germany) Morrissey, A. C., Sbordone, F., Pashley-Johnson, F., Micallef, A. S., van de Worp, B., Zaquen, N., Egodawatta, P., Delafresnaye, L., Michalek, L., Barner-Kowollik, C. 2026: e03580

  Abstract

  Understanding the adsorption behavior of charged molecular species at functionalized polymer interfaces is critical for advancing surface science and material design. Building upon recent advances in polydopamine (PDA)-mediated polymer grafting, we investigated electrostatic adsorption at cationic polymer brush surfaces. Using a grafting-to approach, we covalently attached poly(2-trimethylammonioethyl methacrylate chloride) (PTMAEMA) to PDA-coated stonewool fibers and characterized the resulting charged interface via x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). We employed perfluorooctanoic acid (PFOA) as a model anionic adsorbate to investigate binding at a quaternary amine-functionalized surface. Batch equilibrium sorption studies revealed concentration-dependent adsorption kinetics, achieving three times higher binding affinity for PTMAEMA-functionalized fibers at concentrations ranging from 0.5 to 5.0 g L- 1, with equilibrium reached within 10 min. XPS analysis confirmed the successful surface functionalization with distinct nitrogen environments at 395.5 eV (PDA) and 398.5 eV (quaternary nitrogen), while thermogravimetric data indicated an organic loading of close to 28%. Our findings demonstrate that PDA-mediated polymer grafting provides a versatile platform for creating well-defined charged interfaces with tunable adsorption characteristics, and provides a methodology to explore fundamental adsorption phenomena at polymer-liquid interfaces.

  View details for DOI 10.1002/chem.202503580

  View details for PubMedID 41553099

• Skin-like drift-free biosensors with stretchable diode-connected organic field-effect transistors NATURE ELECTRONICS Zhao, C., Park, J., Maula, D., Yuan, Y., Zhong, D., Wang, W., Liu, Q., Xu, C., Zheng, Y., Mow, R. K., Jiang, Y., Xu, C., Lyu, H., Michalek, L., Berman, A., Jiang, Y., Wei, S., Zhu, C., Wu, C., Abramson, A., Kim, E., Ji, X., Yu, Z., Shi, J., Khatib, M., Shi, B., Bao, Z. 2025

  View details for DOI 10.1038/s41928-025-01465-4

  View details for Web of Science ID 001586240900001

• Bioinspired Metal Binding Interfaces for Continuous Metal Removal from Water. ACS applied materials & interfaces Morrissey, A. C., Sbordone, F., Sprake, W., Michalek, L., Ghijzen, D., van de Worp, B., Zaquen, N., Delafresnaye, L., Egodawatta, P., Barner-Kowollik, C. 2025

  Abstract

  Herein, we introduce a water flow system that combines adhesion with the selective complexation of metal ions from aqueous solutions, enabling the removal of multiple metal ions from polluted water. Specifically, we utilize a bioinspired polymeric system based on l-3,4-dihydroxyphenylalanine (l-DOPA) carrying a terpyridine functionality that efficiently coats stone wool fibers in a continuous flow coating process, enabling the in-line generation of water purification cartridges. We assess the carefully characterized coated fibers for their metal removal capacities in single metal solutions as well as multi-metal solutions to determine binding affinities via inductively coupled plasma mass spectrometry (ICP-MS). The findings of these studies reveal that chromium (Cr), copper (Cu), and lead (Pb) are adsorbed efficiently by the ligand-coated stone wool fibers. Moreover, we investigated the long-term application of the coated fibers, which displayed no saturation for the removal of Cu over 15 column volumes, making the introduced coating system an excellent candidate for applications in urban stormwater management.

  View details for DOI 10.1021/acsami.5c06671

  View details for PubMedID 40470754

• Electrochemical formation of bis(fluorosulfonyl)imide-derived solid-electrolyte interphase at Li-metal potential. Nature chemistry Yu, W., Lin, K. Y., Boyle, D. T., Tang, M. T., Cui, Y., Chen, Y., Yu, Z., Xu, R., Lin, Y., Feng, G., Huang, Z., Michalek, L., Li, W., Harris, S. J., Jiang, J. C., Abild-Pedersen, F., Qin, J., Cui, Y., Bao, Z. 2024

  Abstract

  Lithium bis(fluorosulfonyl)imide-based liquid electrolytes are promising for realizing high coulombic efficiency and long cycle life in next-generation Li-metal batteries. However, the role of anions in the formation of the solid-electrolyte interphase remains unclear. Here we combine electrochemical analyses and X-ray photoelectron spectroscopy measurements, both with and without sample washing, together with computational simulations, to propose the reaction pathways of electrolyte decomposition and correlate the interphase component solubility with the efficacy of passivation. We discover that not all the products derived from interphase-forming reactions are incorporated into the resulting passivation layer, with a notable portion present in the liquid electrolyte. We also find that the high-performance electrolytes can afford a sufficiently passivating interphase with minimized electrolyte decomposition, by incorporating more anion-decomposition products. Overall, this work presents a systematic approach of coupling electrochemical and surface analyses to paint a comprehensive picture of solid-electrolyte interphase formation, while identifying the key attributes of high-performance electrolytes to guide future designs.

  View details for DOI 10.1038/s41557-024-01689-5

  View details for PubMedID 39622915

  View details for PubMedCentralID 6538711

• A Transparent, Patternable, and Stretchable Conducting Polymer Solid Electrode for Dielectric Elastomer Actuators ADVANCED FUNCTIONAL MATERIALS Kim, E., Lai, J., Michalek, L., Wang, W., Xu, C., Lyu, H., Yu, W., Park, H., Tomo, Y., Root, S. E., Lee, B., Park, J., Park, B., Wei, S., Zhao, C., Bao, Z. 2024

  View details for DOI 10.1002/adfm.202411880

  View details for Web of Science ID 001300258000001

• Printable, stretchable metal-vapor-desorption layers for high-fidelity patterning in soft, freeform electronics. Nature communications Jeong, S., Yoon, H., Michalek, L. F., Kim, G., Kim, J., Seo, J., Kim, D., Park, H., Lee, B., Hong, Y. 2024; 15 (1): 7209

  Abstract

  High-fidelity patterning of thin metal films on arbitrary soft substrates promises integrated circuits and devices that can significantly augment the morphological functionalities of freeform electronics. However, existing patterning methods that decisively rely on prefabricated rigid masks are severely incompatible with myriad surfaces. Here, we report printable, stretchable metal-vapor-desorption layers (s-MVDLs) that can enable high-fidelity patterning of thin metal films on freeform polymeric surfaces. The printed rubbery matrix with highly mobile chains effectively repels various metal vapors from the surface and inhibits their condensation, thereby allowing selective metal deposition. The s-MVDLs are printed by direct ink writing techniques, enabling customizable and scalable thin metal patterns ranging from the micrometer to millimeter scale with high fidelity. Furthermore, the superior stretchability and mechanical robustness of the s-MVDLs allow highly compliant deformation along the substrates, enabling the construction of unconventional circuits and devices on multi-curvature, non-developable, and stretchable surfaces.

  View details for DOI 10.1038/s41467-024-51585-2

  View details for PubMedID 39174549

• Shape-memory-assisted self-healing of macroscopic punctures via high-energy-density periodic dynamic polymers with tunable actuation temperature MATTER Shi, Y., Cooper, C. B., Nogusa, T., Lai, J., Lyu, H., Khatib, M., Xu, C., Michalek, L., Bao, Z. 2024; 7 (6)

  View details for DOI 10.1016/j.matt.2024.03.013

  View details for Web of Science ID 001259507400001

• A bioinspired approach to reversibly metal binding interfaces RSC APPLIED POLYMERS Morrissey, A. C., Jayalatharachchi, V., Michalek, L., Egodawatta, P., Zaquen, N., Delafresnaye, L., Barner-Kowollik, C. 2024; 2 (3): 490-496

  View details for DOI 10.1039/d4lp00010b

  View details for Web of Science ID 001561606900001

• Tuning polymer-backbone coplanarity and conformational order to achieve high-performance printed all-polymer solar cells. Nature communications Wu, Y., Yuan, Y., Sorbelli, D., Cheng, C., Michalek, L., Cheng, H. W., Jindal, V., Zhang, S., LeCroy, G., Gomez, E. D., Milner, S. T., Salleo, A., Galli, G., Asbury, J. B., Toney, M. F., Bao, Z. 2024; 15 (1): 2170

  Abstract

  All-polymer solar cells (all-PSCs) offer improved morphological and mechanical stability compared with those containing small-molecule-acceptors (SMAs). They can be processed with a broader range of conditions, making them desirable for printing techniques. In this study, we report a high-performance polymer acceptor design based on bithiazole linker (PY-BTz) that are on par with SMAs. We demonstrate that bithiazole induces a more coplanar and ordered conformation compared to bithiophene due to the synergistic effect of non-covalent backbone planarization and reduced steric encumbrances. As a result, PY-BTz shows a significantly higher efficiency of 16.4% in comparison to the polymer acceptors based on commonly used thiophene-based linkers (i.e., PY-2T, 9.8%). Detailed analyses reveal that this improvement is associated with enhanced conjugation along the backbone and closer interchain π-stacking, resulting in higher charge mobilities, suppressed charge recombination, and reduced energetic disorder. Remarkably, an efficiency of 14.7% is realized for all-PSCs that are solution-sheared in ambient conditions, which is among the highest for devices prepared under conditions relevant to scalable printing techniques. This work uncovers a strategy for promoting backbone conjugation and planarization in emerging polymer acceptors that can lead to superior all-PSCs.

  View details for DOI 10.1038/s41467-024-46493-4

  View details for PubMedID 38461153

  View details for PubMedCentralID 8440764

• Tuning the Mobility of Indacenodithiophene-Based Conjugated Polymers via Coplanar Backbone Engineering CHEMISTRY OF MATERIALS Ji, X., Cheng, H., Schuster, N. J., LeCroy, G. S., Zhang, S., Wu, Y., Michalek, L., Nguyen, B. T., Chiong, J. A., Schrock, M., Tomo, Y., Rech, J., Salleo, A., Gam, S., Lee, G., Tok, J., Bao, Z. 2023; 36 (1): 256-265

  View details for DOI 10.1021/acs.chemmater.3c02006

  View details for Web of Science ID 001139519300001

• Sequence-dependent self-assembly of supramolecular nanofibers in periodic dynamic block copolymers JOURNAL OF MATERIALS CHEMISTRY A Phong, J. K., Cooper, C. B., Michalek, L., Lin, Y., Nishio, Y., Shi, Y., Gong, H., Vigil, J. A., Ilavsky, J., Kuzmenko, I., Bao, Z. 2023

  View details for DOI 10.1039/d3ta06695a

  View details for Web of Science ID 001125326700001

• Degradable semiconducting polymers without long-range order for on-demand degradation of transient electronics JOURNAL OF MATERIALS CHEMISTRY C Chiong, J. A., Michalek, L., Pena-Alcantara, A. E., Ji, X., Schuster, N. J., Bao, Z. 2023

  View details for DOI 10.1039/d3tc03079b

  View details for Web of Science ID 001090295600001

• Tunable 1D and 2D Polyacrylonitrile Nanosheet Superstructures. ACS nano Gong, H., Patino, D. U., Ilavsky, J., Kuzmenko, I., Peña-Alcántara, A. E., Zhu, C., Coffey, A. H., Michalek, L., Elabd, A., Gao, X., Chen, S., Xu, C., Yan, H., Jiang, Y., Wang, W., Peng, Y., Zeng, Y., Lyu, H., Moon, H., Bao, Z. 2023

  Abstract

  Carbon superstructures are widely applied in energy and environment-related areas. Among them, the flower-like polyacrylonitrile (PAN)-derived carbon materials have shown great promise due to their high surface area, large pore volume, and improved mass transport. In this work, we report a versatile and straightforward method for synthesizing one-dimensional (1D) nanostructured fibers and two-dimensional (2D) nanostructured thin films based on flower-like PAN chemistry by taking advantage of the nucleation and growth behavior of PAN. The resulting nanofibers and thin films exhibited distinct morphologies with intersecting PAN nanosheets, which formed through rapid nucleation on existing PAN. We further constructed a variety of hierarchical PAN superstructures based on different templates, solvents, and concentrations. These PAN nanosheet superstructures can be readily converted to carbon superstructures. As a demonstration, the nanostructured thin film exhibited a contact angle of ∼180° after surface modification with fluoroalkyl monolayers, which is attributed to high surface roughness enabled by the nanosheet assemblies. This study offers a strategy for the synthesis of nanostructured carbon materials for various applications.

  View details for DOI 10.1021/acsnano.3c05792

  View details for PubMedID 37668312

• Genetically targeted chemical assembly of polymers specifically localized extracellularly to surface membranes of living neurons. Science advances Zhang, A., Loh, K. Y., Kadur, C. S., Michalek, L., Dou, J., Ramakrishnan, C., Bao, Z., Deisseroth, K. 2023; 9 (32): eadi1870

  Abstract

  Multicellular biological systems, particularly living neural networks, exhibit highly complex organization properties that pose difficulties for building cell-specific biocompatible interfaces. We previously developed an approach to genetically program cells to assemble structures that modify electrical properties of neurons in situ, opening up the possibility of building minimally invasive cell-specific structures and interfaces. However, the efficiency and biocompatibility of this approach were challenged by limited membrane targeting of the constructed materials. Here, we design a method for highly localized expression of enzymes targeted to the plasma membrane of primary neurons, with minimal intracellular retention. Next, we show that polymers synthesized in situ by this approach form dense extracellular clusters selectively on the targeted cell membrane and that neurons remain viable after polymerization. Last, we show generalizability of this method across a range of design strategies. This platform can be readily extended to incorporate a broad diversity of materials onto specific cell membranes within tissues and may further enable next-generation biological interfaces.

  View details for DOI 10.1126/sciadv.adi1870

  View details for PubMedID 37556541

• Environmentally stable and stretchable polymer electronics enabled by surface-tethered nanostructured molecular-level protection. Nature nanotechnology Zheng, Y., Michalek, L., Liu, Q., Wu, Y., Kim, H., Sayavong, P., Yu, W., Zhong, D., Zhao, C., Yu, Z., Chiong, J. A., Gong, H., Ji, X., Liu, D., Zhang, S., Prine, N., Zhang, Z., Wang, W., Tok, J. B., Gu, X., Cui, Y., Kang, J., Bao, Z. 2023

  Abstract

  Stretchable polymer semiconductors (PSCs) are essential for soft stretchable electronics. However, their environmental stability remains a longstanding concern. Here we report a surface-tethered stretchable molecular protecting layer to realize stretchable polymer electronics that are stable in direct contact with physiological fluids, containing water, ions and biofluids. This is achieved through the covalent functionalization of fluoroalkyl chains onto a stretchable PSC film surface to form densely packed nanostructures. The nanostructured fluorinated molecular protection layer (FMPL) improves the PSC operational stability over an extended period of 82 days and maintains its protection under mechanical deformation. We attribute the ability of FMPL to block water absorption and diffusion to its hydrophobicity and high fluorination surface density. The protection effect of the FMPL (~6 nm thickness) outperforms various micrometre-thick stretchable polymer encapsulants, leading to a stable PSC charge carrier mobility of ~1 cm2 V-1 s-1 in harsh environments such as in 85-90%-humidity air for 56 days or in water or artificial sweat for 42 days (as a benchmark, the unprotected PSC mobility degraded to 10-6 cm2 V-1 s-1 in the same period). The FMPL also improved the PSC stability against photo-oxidative degradation in air. Overall, we believe that our surface tethering of the nanostructured FMPL is a promising approach to achieve highly environmentally stable and stretchable polymer electronics.

  View details for DOI 10.1038/s41565-023-01418-y

  View details for PubMedID 37322142

• Shear-aligned large-area organic semiconductor crystals through extended pi-pi interaction JOURNAL OF MATERIALS CHEMISTRY C Zhang, S., Talnack, F., Jousselin-Oba, T., Bhat, V., Wu, Y., Lei, Y., Tomo, Y., Gong, H., Michalek, L., Zhong, D., Wu, C., Yassar, A., Mannsfeld, S., Risko, C., Frigoli, M., Bao, Z. 2023

  View details for DOI 10.1039/d3tc01311a

  View details for Web of Science ID 001006838400001

• Autonomous alignment and healing in multilayer soft electronics using immiscible dynamic polymers. Science (New York, N.Y.) Cooper, C. B., Root, S. E., Michalek, L., Wu, S., Lai, J. C., Khatib, M., Oyakhire, S. T., Zhao, R., Qin, J., Bao, Z. 2023; 380 (6648): 935-941

  Abstract

  Self-healing soft electronic and robotic devices can, like human skin, recover autonomously from damage. While current devices use a single type of dynamic polymer for all functional layers to ensure strong interlayer adhesion, this approach requires manual layer alignment. In this study, we used two dynamic polymers, which have immiscible backbones but identical dynamic bonds, to maintain interlayer adhesion while enabling autonomous realignment during healing. These dynamic polymers exhibit a weakly interpenetrating and adhesive interface, whose width is tunable. When multilayered polymer films are misaligned after damage, these structures autonomously realign during healing to minimize interfacial free energy. We fabricated devices with conductive, dielectric, and magnetic particles that functionally heal after damage, enabling thin-film pressure sensors, magnetically assembled soft robots, and underwater circuit assembly.

  View details for DOI 10.1126/science.adh0619

  View details for PubMedID 37262169

• Effect of Molecular Weight on the Morphology of a Polymer Semiconductor-Thermoplastic Elastomer Blend ADVANCED ELECTRONIC MATERIALS Pena-Alcantara, A., Nikzad, S., Michalek, L., Prine, N., Wang, Y., Gong, H., Ponte, E., Schneider, S., Wu, Y., Root, S. E., He, M., Tok, J., Gu, X., Bao, Z. 2023

  View details for DOI 10.1002/aelm.202201055

  View details for Web of Science ID 000915963500001

• Realizing Intrinsically Stretchable Semiconducting Polymer Films by Nontoxic Additives ACS MATERIALS LETTERS Cheng, H., Zhang, S., Michalek, L., Ji, X., Luo, S., Cooper, C. B., Gong, H., Nikzad, S., Chiong, J. A., Wu, Y., Zheng, Y., Liu, Q., Zhong, D., Lei, Y., Tomo, Y., Wei, K., Zhou, D., Tok, J., Bao, Z. 2022; 4 (11): 2328-2336

  View details for DOI 10.1021/acsmaterialslett.2c00749

  View details for Web of Science ID 000898404900001

• Photostationary State in Dynamic Covalent Networks ACS MACRO LETTERS Chambers, L. C., Barner-Kowollik, C., Barner, L., Michalek, L., Frisch, H. 2022; 11 (4): 532-536

  Abstract

  We explore a cross-linked polymer network based on a visible light photodynamic [2 + 2] cycloaddition driven by styrylpyrene chemistry. Based on a polymer backbone with pendent styrylpyrene units, the network can be formed by using λ = 450 nm irradiation. Upon irradiation with λ = 340 nm, a photostationary state is generated within the network with ∼17% of the styrylpyrene units open compared to close to 2% in the visible light cured state. The limited fraction of open [2 + 2] couples is caused by their proximity and is in sharp contrast to solution experiments on the photoreactive moiety. Thus, the polymer network retains its mechanical properties even at the photostationary point. We hypothesize that the application of an additional stimulus could serve as a second gate for inducing network disintegration by spacing the [2 + 2] units during ultraviolet irradiation.

  View details for DOI 10.1021/acsmacrolett.2c00097

  View details for Web of Science ID 000790005700019

  View details for PubMedID 35575324

• A versatile and straightforward process to turn plastics into antibacterial materials POLYMER CHEMISTRY Hadiouch, S., Maresca, M., Gigmes, D., Machado, G., Maurel-Pantel, A., Frik, S., Saunier, J., Deniset-Besseau, A., Yagoubi, N., Michalek, L., Barner-Kowollik, C., Guillaneuf, Y., Lefay, C. 2021; 13 (1): 69-79

  View details for DOI 10.1039/d1py01344k

  View details for Web of Science ID 000724952500001

• A Versatile Light-Triggered Radical-Releasing Surface Coating Technology ADVANCED MATERIALS TECHNOLOGIES Boase, N. R. B., Michalek, L., Hooker, J. P., Fairfull-Smith, K. E. 2022; 7 (4)

  View details for DOI 10.1002/admt.202100898

  View details for Web of Science ID 000707837600001

• Light-Gated Control of Conformational Changes in Polymer Brushes ADVANCED MATERIALS TECHNOLOGIES Bialas, S., Krappitz, T., Walden, S. L., Kalayci, K., Kodura, D., Frisch, H., MacLeod, J. M., Nelson, A., Michalek, L., Barner-Kowollik, C. 2022; 7 (4)

  View details for DOI 10.1002/admt.202100347

  View details for Web of Science ID 000671534700001

• Chain-Length-Dependent Photolysis of <i>ortho</i>-Nitrobenzyl-Centered Polymers ACS MACRO LETTERS Bachmann, J., Petit, C., Michalek, L., Catel, Y., Blasco, E., Blinco, J. P., Unterreiner, A., Barner-Kowollik, C. 2021; 10 (4): 447-452

  Abstract

  Herein, we demonstrate that the photochemical cleavage of linear polymers containing a midchain photocleavable moiety strongly depends on the chain length. Based on an ortho-nitrobenzyl (oNB) difunctional reversible addition-fragmentation chain-transfer agent, well-defined poly(methyl acrylate)s (Mn = 1.59-67.6 kg mol-1, Đ = 1.3-1.4) were synthesized following a core-first approach. Photolysis at λmax = 350 nm of the ortho-nitrobenzyl moiety led to the generation of equally sized polymer segments. The rate of oNB-driven polymer fragmentation, which can be well described by first-order kinetics, strongly increases with increasing molecular weight in a nonlinear fashion, potentially caused by entropic considerations and is compared to the ideal chain model. The current study thus demonstrates that polymer photolysis is dependent on the polymer chain length, with critical implications for photocleavable network design.

  View details for DOI 10.1021/acsmacrolett.1c00057

  View details for Web of Science ID 000643543200008

  View details for PubMedID 35549234

• UV-induced photolysis of polyurethanes CHEMICAL COMMUNICATIONS Petit, C., Bachmann, J., Michalek, L., Catel, Y., Blasco, E., Blinco, J. P., Unterreiner, A., Barner-Kowollik, C. 2021; 57 (23): 2911-2914

  Abstract

  Waste production associated with the use of non-degradable materials in packaging is a growing cause of environmental concern, with the polyurethane (PU) class being notorious for their lack of degradability. Herein, we incorporate photosensitive ortho-Nitrobenzyl units into PUs to achieve controllable photodegradability. We performed their photolysis in solution and thin films which can inform the design of degradable adhesives.

  View details for DOI 10.1039/d1cc00124h

  View details for Web of Science ID 000630134800014

  View details for PubMedID 33616594

• Mapping Photochemical Reactivity Profiles on Surfaces JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Michalek, L., Krappitz, T., Mundsinger, K., Walden, S. L., Barner, L., Barner-Kowollik, C. 2020; 142 (52): 21651-21655

  Abstract

  Herein, we introduce a comprehensive methodology to map the reactivity of photochemical systems on surfaces. The reactivity of photoreactive groups in solution often departs from their corresponding solution absorption spectra. On surfaces, the relationship between the surface absorption spectra and reactivity remains unexplored. Thus, herein, the reactivity of an o-methylbenzaldehyde and a tetrazole, as ligation partners for maleimide functionalized polymers, was investigated when the reactive moieties are tethered to a surface. The ligation reaction of tetrazole functionalized surfaces was found to proceed rapidly leading to high grafting densities, while o-methylbenzaldehyde functionalized substrates required longer irradiation times and resulted in lower surface coverage at the same wavelength (330 nm). Critically, wavelength resolved reactivity profiles were found to closely match the surface absorption spectra, contrary to previously reported red shifts in solution for the same chromophores.

  View details for DOI 10.1021/jacs.0c11485

  View details for Web of Science ID 000605189000009

  View details for PubMedID 33337866

• Two Grapes Short of a Fruit Salad: Raspberry-, Strawberry-, and Seedpod-Like Organic Microspheres via Colloidal Nanotemplating ACS MACRO LETTERS Mundsinger, K., Schmitt, C. W., Michalek, L., Susewind, M., Hofe, T., Barner-Kowollik, C., Barner, L. 2020; 9 (12): 1785-1792

  Abstract

  The morphology of surfaces critically influences their interaction with the surrounding phase. Herein, we report a modular approach for the synthesis of organic-inorganic raspberry-, strawberry-, and seedpod-like particles to template the porosity of superficially porous particles. Divinylbenzene (DVB) microspheres were employed as core particles, which were modified with polar and nonpolar polymer shells. Subsequently, silica nanoparticle templates were covalently tethered to said particles. Further grafting of polymer shells and subsequent template removal yielded superficially porous core-shell particles. In addition, we introduce a facile procedure for the synthesis of superficially porous particles without distinguishable core-shell morphology. Organic seedpod-like particles were prepared from DVB and silica templates, yielding superficially porous particles after template removal. The surface morphology of the templated particles was investigated via scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) was performed to prove the chemical modification of the particle surfaces.

  View details for DOI 10.1021/acsmacrolett.0c00688

  View details for Web of Science ID 000600159500011

  View details for PubMedID 35653683

• 2D Fabrication of Tunable Responsive Interpenetrating Polymer Networks from a Single Photoresist ADVANCED FUNCTIONAL MATERIALS Michalek, L., Bialas, S., Walden, S. L., Bloesser, F. R., Frisch, H., Barner-Kowollik, C. 2020; 30 (48)

  View details for DOI 10.1002/adfm.202005328

  View details for Web of Science ID 000569136000001

• Wavelength-Selective Folding of Single Polymer Chains with Different Colors of Visible Light MACROMOLECULAR RAPID COMMUNICATIONS Frisch, H., Kodura, D., Bloesser, F. R., Michalek, L., Barner-Kowollik, C. 2020; 41 (1): e1900414

  Abstract

  Photochemistry allows chemists to exert control over chemical reactions with spatiotemporal precision. Furthermore, light holds the potential to not only gate when and where but also which reaction takes place. Herein, two photocycloaddition reactions-initiated by different colors of visible light-are utilized to control the intramolecular crosslinking of single polymer chains. Irradiation with blue light (λmax = 470 nm) triggers a [2 + 2] photocycloaddition inducing an initial intramolecular crosslinking reaction, whereas subsequent irradiation with violet light (λmax = 415 nm) induces a [4 + 4] photocycloaddition, fully compacting the dual photoreactive polymer into a single-chain nanoparticle. Importantly, both crosslinked states are accessible under ultra-mild conditions requiring nothing but two different colors of visible light. The reported strategy of wavelength-selective crosslinking degrees provides key potential to be translated into materials applications for the remote control of mechanical properties on the molecular level.

  View details for DOI 10.1002/marc.201900414

  View details for Web of Science ID 000485624700001

  View details for PubMedID 31507017

• Adaptable and Reprogrammable Surfaces ADVANCED MATERIALS Goldmann, A. S., Boase, N. R. B., Michalek, L., Blinco, J. P., Welle, A., Barner-Kowollik, C. 2019; 31 (40): e1902665

  Abstract

  Establishing control over chemical reactions on interfaces is a key challenge in contemporary surface and materials science, in particular when introducing well-defined functionalities in a reversible fashion. Reprogrammable, adaptable and functional interfaces require sophisticated chemistries to precisely equip them with specific functionalities having tailored properties. In the last decade, reversible chemistries-both covalent and noncovalent-have paved the way to precision functionalize 2 or 3D structures that provide both spatial and temporal control. A critical literature assessment reveals that methodologies for writing and erasing substrates exist, yet are still far from reaching their full potential. It is thus critical to assess the current status and to identify avenues to overcome the existing limitations. Herein, the current state-of-the-art in the field of reversible chemistry on surfaces is surveyed, while concomitantly identifying the challenges-not only synthetic but also in current surface characterization methods. The potential within reversible chemistry on surfaces to function as true writeable memories devices is identified, and the latest developments in readout technologies are discussed. Finally, we explore how spatial and temporal control over reversible, light-induced chemistries has the potential to drive the future of functional interface design, especially when combined with powerful laser lithographic applications.

  View details for DOI 10.1002/adma.201902665

  View details for Web of Science ID 000481228500001

  View details for PubMedID 31414512

• Quantifying Solvent Effects on Polymer Surface Grafting ACS MACRO LETTERS Michalek, L., Mundsinger, K., Barner, L., Barner-Kowollik, C. 2019; 8 (7): 800-805

  Abstract

  When grafting polymers onto surfaces, the reaction conditions critically influence the resulting interface properties, including the grafting density and molar mass distribution (MMD) on the surface. Herein, we show theoretically and experimentally that the application of poor solvents is beneficial for the "grafting-to" approach. We demonstrate the effect by grafting poly(methyl methacrylate) chains on silica nanoparticles in different solvents and compare the MMD of the polymer in solution before and after grafting via size exclusion chromatography (SEC). The shorter polymer chains are preferentially grafted onto the surface, leading to a distortion effect between the MMD in solution and on surfaces. The molecular weight distortion effect is significantly higher for ethyl acetate (good solvent quality, difference in Mw surface to solution 14%) than for N,N-dimethylacetamide (poor solvent quality, 6%). The difference in MMD on the surface to the solution significantly affects both the surface properties (e.g. the grafting densities) and their determination.

  View details for DOI 10.1021/acsmacrolett.9b00336

  View details for Web of Science ID 000477073700008

  View details for PubMedID 35619509

• Access to Disparate Soft Matter Materials by Curing with Two Colors of Light ADVANCED MATERIALS Bialas, S., Michalek, L., Marschner, D. E., Krappitz, T., Wegener, M., Blinco, J., Blasco, E., Frisch, H., Barner-Kowollik, C. 2019; 31 (8): e1807288

  Abstract

  A platform technology for multimaterial photoresists that can be orthogonally cured by disparate colors of light is introduced. The resist's photochemistry is designed such that one wavelength selectively activates the crosslinking of one set of macromolecules, while a different wavelength initiates network formation of a different set of chains. Each wavelength is thus highly selective towards a specific photoligation reaction within the resist. Critically, the shorter wavelength does not induce ligation of the longer wavelength selective species within the same resist mixture, defined as "wavelength orthogonality." Uniquely, this dual-color addressable resist system allows generating spatially resolved soft matter materials by simply selecting the curing wavelength, thus constituting a wavelength-orthogonal multimaterial resist with applications ranging from coatings to 3D additive manufacturing of multimaterial architectures.

  View details for DOI 10.1002/adma.201807288

  View details for Web of Science ID 000459798700024

  View details for PubMedID 30614578

• The long and the short of polymer grafting POLYMER CHEMISTRY Michalek, L., Mundsinger, K., Barner-Kowollik, C., Barner, L. 2019; 10 (1): 54-59

  View details for DOI 10.1039/c8py01470a

  View details for Web of Science ID 000453816000004

• Polyselenoureas via Multicomponent Polymerizations Using Elemental Selenium as Monomer ACS MACRO LETTERS Tuten, B. T., Bloesser, F. R., Marshall, D. L., Michalek, L., Schmitt, C. W., Blanksby, S. J., Barner-Kowollik, C. 2018; 7 (8): 898-903

  Abstract

  Multicomponent polymerizations (MCPs) have emerged as a powerful tool in the synthesis of advanced, sequence-regulated polymers based on their mild reaction conditions, ease of use, and high atom economy. Herein, we exploit MCP methodology to introduce elemental selenium into a polymer chain, accessing a unique polymer class,i.e., polyselenoureas. These polyselenoureas can be synthesized from a broad range of commercially available starting materials, in a simple ambient temperature one-step procedure. The incorporation of selenium directly into the polymer backbone provides a unique handle for polymer characterization based on the distinctive isotope profiles exposed by high-resolution mass spectrometry, along with diagnostic signals observed in infrared and X-ray photoelectron spectroscopies. In addition, diffusion ordered spectroscopy provides access to hydrodynamic diameter information on the generated unique polymer class.

  View details for DOI 10.1021/acsmacrolett.8b00428

  View details for Web of Science ID 000444659000002

  View details for PubMedID 35650962

• A Subtractive Photoresist Platform for Micro- and Macroscopic 3D Printed Structures ADVANCED FUNCTIONAL MATERIALS Zieger, M. M., Mueller, P., Blasco, E., Petit, C., Hahn, V., Michalek, L., Mutlu, H., Wegener, M., Barner-Kowollik, C. 2018; 28 (29)

  View details for DOI 10.1002/adfm.201801405

  View details for Web of Science ID 000438708600019

• The role of surface oxides on hydrogen sorption kinetics in titanium thin films APPLIED SURFACE SCIENCE Hadjixenophontos, E., Michalek, L., Roussel, M., Hirscher, M., Schmitz, G. 2018; 441: 324-330

  View details for DOI 10.1016/j.apsusc.2018.02.044

  View details for Web of Science ID 000427816400039

• Polymer on Top: Current Limits and Future Perspectives of Quantitatively Evaluating Surface Grafting ADVANCED MATERIALS Michalek, L., Barner, L., Barner-Kowollik, C. 2018; 30 (21): e1706321

  Abstract

  Well-defined polymer strands covalently tethered onto solid substrates determine the properties of the resulting functional interface. Herein, the current approaches to determine quantitative grafting densities are assessed. Based on a brief introduction into the key theories describing polymer brush regimes, a user's guide is provided to estimating maximum chain coverage and-importantly-examine the most frequently employed approaches for determining grafting densities, i.e., dry thickness measurements, gravimetric assessment, and swelling experiments. An estimation of the reliability of these determination methods is provided via carefully evaluating their assumptions and assessing the stability of the underpinning equations. A practical access guide for comparatively and quantitatively evaluating the reliability of a given approach is thus provided, enabling the field to critically judge experimentally determined grafting densities and to avoid the reporting of grafting densities that fall outside the physically realistic parameter space. The assessment is concluded with a perspective on the development of advanced approaches for determination of grafting density, in particular, on single-chain methodologies.

  View details for DOI 10.1002/adma.201706321

  View details for Web of Science ID 000434032600009

  View details for PubMedID 29512237

• Engineering Nitroxide Functional Surfaces Using Bioinspired Adhesion LANGMUIR Woehlk, H., Steinkoenig, J., Lang, C., Michalek, L., Trouillet, V., Krolla, P., Goldmann, A. S., Barner, L., Blinco, J. P., Barner-Kowollik, C., Fairfull-Smith, K. E. 2018; 34 (10): 3264-3274

  Abstract

  We pioneer a versatile surface modification strategy based on mussel-inspired oxidative catecholamine polymerization for the design of nitroxide-containing thin polymer films. A 3,4-dihydroxy-l-phenylalanine (l-DOPA) monomer equipped with a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-derived oxidation-labile hydroxylamine functional group is employed as a universal coating agent to generate polymer scaffolds with persistent radical character. Various types of materials including silicon, titanium, ceramic alumina, and inert poly(tetrafluoroethylene) (PTFE) were successfully coated with poly(DOPA-TEMPO) thin films in a one-step dip-coating procedure under aerobic, slightly alkaline (pH 8.5) conditions. Steadily growing polymer films (∼1.1 nm h-1) were monitored by ellipsometry, and their thicknesses were critically compared with those obtained from atomic force microscopic cross-sectional profiles. The heterogeneous composition of surface-adherent nitroxide scaffolds examined by X-ray photoelectron spectroscopy was correlated to that examined by in-solution polymer analysis via high-resolution electrospray ionization mass spectrometry, revealing oligomeric structures with up to six repeating units, mainly composed of covalently linked dihydroxyindole along the polymer backbone. Critically, the reversible redox-active character of the nitroxide-containing polymer scaffolds was investigated by cyclic voltammetric measurements, revealing a convenient and facile access route to electrochemically active nitroxide polymer coatings with potential application in electronic devices such as organic radical batteries.

  View details for DOI 10.1021/acs.langmuir.7b03755

  View details for Web of Science ID 000427661100013

  View details for PubMedID 29442516