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Properties of the surface-modified layer of plasma-oxidized poly(dimethylsiloxane)

MRS Online Proceedings Library 2006年第1期924卷 1-6页

作者： Kristen L. Mills Xiaoyue Zhu Donghee Lee Shuichi Takayama M. D. Thouless Department of Mechanical Engineering University of Michigan Ann Arbor USA Department of Biomedical Engineering University of Michigan Ann Arbor USA Macromolecular Science and Engineering Program University of Michigan Ann Arbor USA Department of Materials Science and Engineering University of Michigan Ann Arbor USA

Exposure of poly(dimethylsiloxane) (PDMS) to oxygen plasma creates a thin, stiff surface-modified layer that reaches a submicron depth. Due to a significant modulus mismatch between the stiff surface-modified layer and the compliant bulk PDMS the surface-modified layer forms intricate patterns of surface buckles when under compressive stress and nano-cracks when under tensile stress. It is desirable to be able to design patterns of nano-cracks, or at least to have an understanding of them. Among the properties necessary to do this are the thickness and elastic modulus of the surface-modified layer. Due to the very small length scale of the surface-modified layer, it is a significant challenge to measure these properties. In this proceedings paper, a two-step method is described for determining the thickness and elastic modulus of the surface-modified layer using the atomic force microscope (AFM). First, nanoindentation is performed from which the bending stiffness of the surface-modified layer is calculated. Second, the surface-modified layer thickness is determined by using phase imaging on the cross-section of oxidized PDMS to map the region of the relatively stiffer surface-modified layer.

关键词： nanoscale elastic properties film

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Assessment of Simple Adhesive Substrates as a Method for Quantifying Microplastics and the Factors Influencing Capture

SSRN

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SSRN 2022年

作者： Rieland, Julie M. Hu, Zeyuan Deese, Julian S. Love, Brian J. Department of Materials Science and Engineering United States Department of Biomedical Engineering United States Macromolecular Science and Engineering Graduate Program 2300 Hayward St Ann ArborMI48109 United States

Microplastics are a growing environmental concern, with a large body of evidence documenting substantial distribution of plastic material in virtually all environmental compartments. Countermeasures that help to bind, aggregate, or coalesce these distributed particles might result in lower human and animal exposures. Pressure sensitive adhesives (PSAs) have been identified as a viable microplastic (MP) capture mechanism with a range of potential use conditions. As with any countermeasure, there is a need to evaluate their collection efficiency, cost, ease of installation, etc. Expanding on previous work, submerged, spray-coated PSAs were investigated as a quick and low-cost quantitative method to assess MP binding in water. Two molecular weights of poly(2-ethylhexyl acrylate) PSA (92k, 950k, and 50:50 bimodal distribution) were applied as spray-coated substrates to compare MP-adhesive interactions. Thin films of PSA (92k 6 ± 1 μm, 950k 4 ± 2 μm, 50:50 BD 6.5 ± 1 μm) were sprayed on borosilicate glass slides using a commercial air brush. Polydisperse nylon-12 particles varying in size from 15-30 µm in diameter were dispersed in aqueous solution between 0.01 and 5 mg mL -1 and agitated under ambient conditions as quantitative comparisons of adhesive wettability and net capture. Mixed assays were also performed comparing binding of common MP species including polyethylene, polystyrene, and polyester particles and fibers to understand how varying composition, size, and form factor affect adsorption. The glass slide method demonstrated linear trends associated with the MP binding to glass slides with respect both to exposure time and MP concentration. The adhesive wettability demonstrates bounding parameters under which high wettability adhesives excel at MP capture but may compromise the integrity of the adhesive film. © 2022, The Authors. All rights reserved.

关键词： Adhesives

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Cross-linked low EW PFSA for high temperature fuel cell

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作者： Ghassemi, H. Zawodzinski, T. Schiraldi, D. Hamrock, S. Department of Macromolecular Science and Engineering Case Western Reserve University Cleveland OH 44106 United States Department of Chemical and Biomolecular Engineering University of Tennessee Knoxville TN 37996 United States 3M Fuel Cell Components Program 3M Company St. Paul MN 55144 United States

ISBN: (纸本)9780841226319

Several approaches have been studied to prepare ionomers for a high temperature proton exchange membrane (PEM) fuel cell. These ionomers were designed to be very low equivalent weight (EW), chemically stable, solvent resistant and highly conductive. The synthetic approaches include grafting, hybrid formation and cross-linking. The most interesting results were obtained from cross-linking of functionalized PFSA ionomers with various cross-linking compounds. New side-chain component multifunctional ionomers have been developed that were cross-linkable during or after membrane fabrication. As a result of this approach, a suite of polymers have been synthesized that, after membrane casting and cross linking show improved solvent resistant, low swelling and excellent proton conductivity. An obvious approach to increase proton conductivity in PSFA materials is to lower the equivalent weight (EW) by increasing the number of protogenic groups. PFSA membranes with EW

关键词： Ionomers

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Direct Interaction between the Transmembrane Helices Stabilize Cytochrome P450 2b4 and Cytochrome B5 Redox Complex

SSRN

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SSRN 2023年

作者： Ramamoorthy, Ayyalusamy Sahoo, Bikash R. Biophysics Program Department of Chemistry Macromolecular Science and Engineering Biomedical Engineering Michigan Neuroscience Institute The University of Michigan Ann ArborMI48109-1055 United States

The catalytic activity of cytochrome P450 2B4 (CYP2B4) is moderated by its cognate redox partner cytochrome b5 (Cyt-b5). The endoplasmic reticulum (ER) membrane and intermolecular transmembrane (TM) interaction between CYP2B4 and Cyt-b5 regulate the substrate catalysis and the reaction rate. This emphasizes the significance of elucidating the molecular basis of CYP2B4 and Cyt-b5 complexation in a membrane environment to better understand the enzymatic activity of CYP2B4. Our previous solid-state NMR studies revealed the membrane topology of the transmembrane domains of these proteins in the free and complex forms. Here, we show the cross-angle complex formation by the single-pass TM domains of CYP2B4 and Cyt-b5, which is mainly driven by several salt-bridges (E2-R128, R21-D104 and K25-D104), using a multimicrosecond molecular dynamic simulation. Additionally, the leucine-zipper residues (L8, L12, L15, L18 and L19 from CYP2B4) and π-stacking between H23 and F20 residues of CYP2B4 and W110 of Cyt-b5 are identified to stabilize the TM-TM complex in the ER membrane. The simulated tilts of the helices in the free and in the complex are in excellent agreement with solid-state NMR results. The TM-TM packing influences a higher order structural stability when compared to the complex formed by the truncated soluble domains of these two proteins. MM/PBSA based binding free energy estimates nearly 100-fold higher binding affinity (ΔG=-2810.68±696.44 kJ/mol) between the soluble domains of the full-length CYP2B4 and Cyt-b5 when embedded in lipid membrane as compared to the TM-domain-truncated soluble domains (ΔG=-27.406±10.32 kJ/mol). The high-resolution full-length CYP2B4-Cyt-b5 complex structure and its dynamics in a native ER membrane environment reported here could aid in the development of approaches to effectively modulate the drug-metabolism activity of CYP2B4. © 2023, The Authors. All rights reserved.

关键词： Lipid bilayers

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Fluorescence lifetime imaging microscopy (FLIM) measures oxygen gradients in microfluidic bioreactors

Fluorescence lifetime imaging microscopy (FLIM) measures oxy...

引用

Biomedical Topical Meeting, BIO 2006

作者： Sud, Dhruv Mehta, Geeta Mehta, Khamir Linderman, Jennifer Takayama, Shuichi Mycek, Mary-Ann Dept. of Biomedical Engineering University of Michigan Ann Arbor MI 48109-2099 United States Dept. of Chemical Engineering University of Michigan Ann Arbor MI 48109-2099 United States Macromolecular Science and Engineering Program University of Michigan Ann Arbor MI 48109-2099 United States Applied Physics Program University of Michigan Ann Arbor MI 48109-2099 United States Comprehensive Cancer Center University of Michigan Ann Arbor MI 48109-2099 United States

A unique FLIM system was employed to quantitatively image extracellular oxygen distributions in perfused micro-bioreactors. We report effects of cell density on oxygen consumption and the first such measurement of oxy... 详细信息

ISBN: (纸本)1557528071

关键词： Oxygen

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Kevlar-based nanocomposites with hierarchical structure

Kevlar-based nanocomposites with hierarchical structure

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15th European Conference on Composite Materials: Composites at Venice, ECCM 2012

作者： Cao, K. Siepermann, C.P. Yang, M. Waas, A.M. Kotov, N.A. Thouless, M.D. Arruda, E.M. Department of Mechanical Engineering University of Michigan Ann Arbor MI 48109 United States Department of Chemical Engineering University of Michigan Ann Arbor MI 48109 United States Department of Aerospace Engineering University of Michigan Ann Arbor MI 48109 United States Department of Materials Science and Engineering University of Michigan Ann Arbor MI 48109 United States Department of Biomedical Engineering University of Michigan Ann Arbor MI 48109 United States Program in Macromolecular Science and Engineering University of Michigan Ann Arbor MI 48109 United States

ISBN: (纸本)9788888785332

Stable dispersions of nanoscale Kevlar fibers with diameters between 3 and 30 nm were obtained by deprotonating macroscale, commercial Kevlar yarns with potassium hydroxide in dimethyl sulfoxide. Those aramid nanofibers were surface-treated with phosphoric acid (PA) and glutaraldehyde (GA), and assembled via layer-by-layer (LBL) and vacuum-assisted filtration method into transversely isotropic films. Through Fourier-transform infrared spectroscopy, transmission-electron microscopy, uniaxial tensile testing and thermo-gravimetric analysis, it was shown that PA hydrolyzes aramid nanofibers which created useful functional groups for surface bonding and GA polymerizes those PA-hydrolyzed nanofibers which served as an inter-fiber crosslinker to improve network properties. A hierarchically structured film made of alternating layers of the high-stiffness, PA/GA-treated, aramid-nanofiber network and high-ductility polyurethane/poly (acrylic acid) was demonstrated to have stiffness and strength exceeding those of commercial Kevlar fiber-woven mats.

关键词： Thermogravimetric analysis

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AI for organic and polymer synthesis

引用

science China Chemistry 2024年第8期67卷 2461-2496页

作者： Xin Hong Qi Yang Kuangbiao Liao Jianfeng Pei Mao Chen Fanyang Mo Hua Lu Wen-Bin Zhang Haisen Zhou Jiaxiao Chen Lebin Su Shuo-Qing Zhang Siyuan Liu Xu Huang Yi-Zhou Sun Yuxiang Wang Zexi Zhang Zhunzhun Yu Sanzhong Luo Xue-Feng Fu Shu-Li You Center of Chemistry for Frontier Technologies Department of ChemistryZhejiang UniversityHangzhou 310027China Center of Basic Molecular Science Department of ChemistryTsinghua UniversityBeijing 100084China Guangzhou National Laboratory Guangzhou 510005China Center for Quantitative Biology Academy for Advanced Interdisciplinary StudiesPeking UniversityBeijing 100871China State Key Laboratory of Molecular Engineering of Polymers Department of Macromolecular ScienceFudan UniversityShanghai 200433China School of Materials Science and Engineering Peking UniversityBeijing 100871China Beijing National Laboratory for Molecular Sciences Center for Soft Matter Science and EngineeringKey Laboratory of Polymer Chemistry and Physics of Ministry of EducationCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China AI for Science(AI4S)-Preferred Program Shenzhen Graduate SchoolPeking UniversityShenzhen 518055China State Key Laboratory of Chemical Biology Shanghai Institute of Organic ChemistryUniversity of Chinese Academy of SciencesChinese Academy of SciencesShanghai 200032China Department of Chemical Sciences National Natural Science Foundation of ChinaBeijing 100085China State Key Laboratory of Organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 200032China

Recent years have witnessed the transformative impact from the integration of artificial intelligence with organic and polymer synthesis. This synergy offers innovative and intelligent solutions to a range of classic problems in synthetic chemistry. These exciting advancements include the prediction of molecular property, multi-step retrosynthetic pathway planning, elucidation of the structure-performance relationship of single-step transformation, establishment of the quantitative linkage between polymer structures and their functions, design and optimization of polymerization process, prediction of the structure and sequence of biological macromolecules, as well as automated and intelligent synthesis platforms. Chemists can now explore synthetic chemistry with unprecedented precision and efficiency, creating novel reactions, catalysts, and polymer materials under the datadriven paradigm. Despite these thrilling developments, the field of artificial intelligence(AI) synthetic chemistry is still in its infancy, facing challenges and limitations in terms of data openness, model interpretability, as well as software and hardware support. This review aims to provide an overview of the current progress, key challenges, and future development suggestions in the interdisciplinary field between AI and synthetic chemistry. It is hoped that this overview will offer readers a comprehensive understanding of this emerging field, inspiring and promoting further scientific research and development.

关键词： organic synthesis polymer synthesis machine learning prediction chemical database automated synthesis

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Design and Optimization of the Porous Metamaterial EM Absorbers in X-band

Design and Optimization of the Porous Metamaterial EM Absorb...

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IEEE International Symposium on Electromagnetic Compatibility (EMC)

作者： Kanat Anurakparadorn Alan Taub Eric Michielssen Macromolecular Science and Engineering Program Department of Material Science and Engineering University of Michigan Ann Arbor Michigan USA Department of Mechanical Engineering University of Michigan Ann Arbor Michigan USA Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor Michigan USA

A strategy that combines experiment and simulation to design and optimize electromagnetic (EM) metamaterial absorbers containing a periodic porous structure is described. The approach provides the ability to produce absorbers that meet multiple user-specified objectives. Using the measured intrinsic properties of the baseline materials as an input to EM-field based computational modelling and optimization, absorption by the studied metamaterials measured by their reflection loss (RL) increases significantly. The resulting metamaterials have the potential for lower cost and lighter weight while providing greater protection than traditional metal gaskets and foams.

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The role of molecular properties on the dimerization of aromatic compounds

arXiv

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arXiv 2017年

作者： Elvati, Paolo Turrentine, Kirk Violi, Angela Department of Mechanical Engineering University of Michigan Ann ArborMI48109-2125 United States Departments of Chemical Engineering Biomedical Engineering Macromolecular Science and Engineering Biophysics Program University of Michigan Ann ArborMI United States

Recent results have shown the presence and importance of oxygen chemistry during the growth of aromatic compounds, leading to the formation of oxygenated structures that have been identified in various environments. Since the formation of polycyclic aromatic compounds (PAC) bridge the formation of gas-phase species with particle inception, in this work we report a detailed analysis of the effects of molecular characteristics on physical growth of PAC via dimerization. We have included oxygen content, mass, type of bonds (rigid versus rotatable), and shape as main properties of the molecules and studied their effect on the propensity of these structures to form homo-molecular and hetero-molecular dimers. Using enhanced sampling molecular dynamics techniques, we have computed the free energy of dimerization in the temperature range 500-1680 K. Initial structures used in this study were obtained from experimental data. The results show that although the effects of shape, presence of oxygen, mass, and internal bonds are tightly intertwined, and their relative importance changes with temperature. In general, mass and the presence of rotatable bonds are the best indicators. The results provide knowledge on the inception step and the role that particle characteristics play during inception. In addition, our study highlights the fact that current models that use stabilomers as monomers for physical aggregation are overestimating the importance of this process during particle nucleation. Copyright © 2017, The Authors. All rights reserved.

关键词： Molecular dynamics

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Terahertz time-domain polarimetry for generalized anistropic and chiral materials 12

Terahertz time-domain polarimetry for generalized anistropic...

引用

Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications XII 2019

作者： Cheng, Gong Choi, Won Jin Jang, Hee-Jeong Kotov, Nicholas A. Norris, Theodore B. Department of Physics University of Michigan Ann ArborMI48109 United States Center for Ultrafast Optical Science University of Michigan Ann ArborMI48109 United States Department of Materials Science and Engineering University of Michigan Ann ArborMI48109 United States Department of Chemical Engineering University of Michigan Ann ArborMI48109 United States Biointerfaces Institute University of Michigan Ann ArborMI48109 United States Program in Macromolecular Science and Engineering University of MI Ann ArborMI48109 United States Department of Electrical Engineering and Computer Science University of Michigan Ann ArborMI48109 United States

ISBN: (纸本)9781510624764

We have developed two terahertz (THz) polarimetric methodologies based on terahertz time-domain spectroscopy (THz-TDS) incorporating three wire-grid polarizers. They require no change to existing THz-TDS setups and are free of any complicated electronic controls and synchronizations. In addition to the standard quantities measured by THz-TDS such as transmission and optical constants, they provide complete information on the anisotropy and chirality for a generalized material through measurements of the full electric field vector and hence the Jones matrix, and calculating specific quantities. Thus terahertz time-domain polarimetry (THz-TDP) can be considered as an upgrade of the conventional THz-TDS, needed for full characterization of anisotropic and chiral materials. In this paper, we describe the details of the experimental settings, mathematical procedures and property quantifications in these methodologies. We present experimental results on an anisotropic polymer sheet showing the effectiveness of the methods, and preliminary data for chiral DNA molecules for the first time in the THz frequency range. © 2019 SPIE.

关键词： Polarimeters

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