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13th International Conference on Miniaturized Systems for Chemistry and Life sciences, MicroTAS 2009

作者： Tung, Yi-Chung Takayama, Shuichi Department of Biomedical Engineering University of Michigan United States Research Center for Applied Sciences Academia Sinica Taiwan Macromolecular Science and Engineering Program University of Michigan United States

ISBN: (纸本)9780979806421

This paper reports a novel fully-disposable, cost-effective microfluidic actuation system requires no fluidic interfacing, and minimal electric connections. The device is constructed of multiple polydimethylsiloxane (PDMS) layers and a glass substrate. Taking advantage of the unique material properties of ionic liquids (IL), the device has long shelf life (> 48 hours) and can be fully functioned in high humidity environments. The microfluidic single and multiple valve and pump devices are demonstrated in the paper. The developed system provides a promising actuation scheme for point-of-care μTAS used in the field. © 2009 CBMS.

关键词： Ionic liquids

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Probe size effects on the microrheology of associating polymer solutions

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Physical Review E 2002年第6期66卷 061504-061504页

作者： Qiang Lu Michael J. Solomon Department of Chemical Engineering and Macromolecular Science and Engineering Program University of Michigan Ann Arbor Michigan 48109-2136

Diffusing wave spectroscopy has been used to investigate the thermally driven displacement of colloidal particles dispersed in solutions of associating polymers (APs). The effect of varying colloidal probe size on the measured particle displacements is studied in particular. Recent theories of microrheology are examined in light of the observed effects. The associating polymer used in this research was a linear polyethylene oxide (PEO) chain (molecular weight 35 000 g/mole) with a Cl14 aliphatic group appended to each end of the PEO. Above a critical concentration, the associating polymers display linear viscoelasticity consistent with the Maxwell model. The concentration of aqueous AP solutions was varied from 0.25 to 4.0 wt. %. At low concentration of APs, the mean square displacement of the colloidal beads was indistinguishable from simple Brownian diffusion in the aqueous solvent. However, at concentrations greater than 0.5 wt. %, the mean square displacement differed from simple diffusion in a way that was found to be consistent with the Maxwell model linear viscoelasticity (LVE) of the AP solutions. Significantly, for the most concentrated solutions, as the probe particle size was varied from 0.3 to 2.2 μm, the observed mean square displacement deviated substantially from the generalized Stokes-Einstein behavior predicted by microrheological theories. Our experiments showed that these deviations could not be attributed to specific physicochemical interactions at the probe-matrix interface, since observed mean square displacements were independent of different probe surface chemistries studied. Moreover, this particle size effect was not observed in semidilute, high molecular weight PEO solutions (molecular weight 4.0×106g/mole). We concluded that possible effects of AP network compressibility and AP depletion at the probe surface could not account for the observed particle size effects. We examined recent reports of the structural heterogeneity in AP solutions

关键词： Colloids

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Influence of conformational change of chain unit on the intrinsic negative thermal expansion of polymers

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Chinese Chemical Letters 2021年第4期32卷 1515-1518页

作者： Qiangsheng Sun Ke Jin Yuhui Huang Jia Guo Thanyada Rungrotmongkol Phornphimon Maitarad Changchun Wang State Key Laboratory of Molecular Engineering of Polymers and Department of Macromolecular Science Fudan UniversityShanghai 200433.China Biocatalyst and Environmental Biotechnology Research Unit Department of BiochemistryFaculty of Science and Program in Bioinformatics and Computational BiologyGraduate SchoolChulalongkom UniversityBangkok 10330Thailand Research Center of Nano Science and Technology Shanghai UniversityShanghai 200444China

Negative thermal expansion(NTE) behavior has roused wide interest for the control of thermomechanical properties of functional *** NTE behaviors have been found in kinds of compounds,it remains challenging for polymers to achieve intrinsic NTE *** this work,we systematically studied the conformational change of dibenzocyclooctadiene(DBCOD) derivatives between chair(C) and twist-boat(TB) forms based on density-functional theo ry(DFT) calculations,and found clear evidence of the relationship between the structure of DBCOD units and the thermal contraction behavior of the related *** order to obtain the polymer with NTE property,two conditions should be met for the thermal contracting DBCOD related units as follows:(i) the TB conformation can turn into C conformation as the temperature increases,and(ii) the volume of C conformation is smaller than that of TB *** rule should offer a guidance to exploration of the new intrinsic NTE polymers in the future.

关键词： Negative thermal expansion Conformational change Polyarylamides Density-functional theory Dibenzocyclooctadiene

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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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2023 IEEE Symposium on Electromagnetic Compatibility and Signal/Power Integrity, EMC+SIPI 2023

作者： Anurakparadorn, Kanat Taub, Alan Michielssen, Eric University of Michigan Macromolecular Science and Engineering Program Department of Material Science and Engineering Ann ArborMI United States University of Michigan Department of Mechanical Engineering Ann ArborMI United States University of Michigan Department of Electrical Engineering and Computer Science Ann ArborMI United States

ISBN: (纸本)9798350309768

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. © 2023 IEEE.

关键词： Metamaterials

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A Comparative Study of the Effect of Compounding Methods and Processing of PLA/GNPs on the Micromorphology and Electrical Conductivity 38

A Comparative Study of the Effect of Compounding Methods and...

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38th Technical Conference of the American Society for Composites, ASC 2023

作者： Anurakparadorn, Kanat Taub, Alan Department of Materials Science and Engineering Macromolecular Science and Engineering Program University of Michigan 2300 Hayward St Ann ArborMI48109 United States Department of Mechanical Engineering University of Michigan 2350 Hayward St Ann ArborMI48109 United States

ISBN: (纸本)9781605956916

In this work, the effects of different compounding and processing techniques on the DC electrical conductivity and density of polylactic acid (PLA)/graphene nanoplatelets (GNPs) composites were studied. It is found from the study that compounding by solution mixing via an ultrasonication technique can provide slightly higher DC electrical conductivity after compression molding than mixing through a twin-screw extruder due to better dispersion quality. In addition, a composite pellet from twin screw extrusion showed a slight increase in DC electrical conductivity and anisotropy when processed by filament extrusion due to the shear alignment of GNPs during the extrusion. The fused deposition modeling (FDM) process yields high anisotropy because the crystallization along the printing path allows gaps and polymer coating between the extruded lines and layers. It was found that the 7.5 wt% GNPs composites exhibited the best properties because it provides the best dispersion quality to meet the percolation threshold. Furthermore, the micromorphology of each sample was also studied to observe the dispersion and porosity inside the composite provided by each fabrication technique. This study can be used as a reference for compounding and processing techniques. © 2023 by DEStech Publications, Inc. and American Society for Composites. All rights reserved.

关键词： Mixing

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Achieving fast discharge and low loss in poly(vinylidene fluoride-cochlorotrifluoroethylene)-graft-polystyrene films by confined ferroelectricity

Achieving fast discharge and low loss in poly(vinylidene flu...

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作者： Guan, Fangxiao Yuan, Zhongzhe Wang, Jing Zhu, Lei Polymer Program Institute of Materials Science and Department of Chemical Materials and Biomolecular Engineering University of Connecticut Storrs CT 06269-3136 United States Department of Macromolecular Science and Engineering Case Western Reserve University Cleveland OH 44106-7202 United States

Although a high electric energy density was recently reported for defect-modified poly(vinylidene fluoride) (PVDF) copolymers at millisecond discharge, they usually deliver less energy at a high pulse rate. In this work, a low loss polystyrene (PS) was grafted as side chains onto the P(VDF-CTFE) main chain. After crystallization of PVDF, dielectric PS side chains were segregated to the crystalline-amorphous interface, forming a finite confinement dielectric layer for ferroelectric PVDF crystals. We speculated that less space charge was induced during electric poling because of the nanoscale confinement effect. Consequently, a fast discharge speed and a relatively high energy density were achieved. © 2010 American Chemical Society.

关键词： Polystyrenes

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Assessment of Simple Adhesive Substrates for Quantifying Microplastics

SSRN

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SSRN 2022年

作者： Rieland, Julie M. Hu, Zeyuan Deese, Julian S. Love, Brian J. The University of Michigan United States Department of Materials Science and Engineering Department of Biomedical Engineering Macromolecular Science and Engineering Graduate Program

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 potential solutions in terms of collection efficiency, cost, ease of installation, etc. Expanding on our previous work, spray-coated PSAs were investigated as submerged surfaces as tools to assess MP binding in aqueous dispersions. Resins containing two differing molecular weights of poly(2-ethylhexyl acrylate) PSA (92k and 950k), and a 50:50 by weight mixture of the two resins were applied as spray-coated substrates to compare the effect of resin composition on MP-adhesive binding. 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 deionized water at concentrations between 0.01 and 5 mg mL -1 and agitated under ambient conditions to assess adhesive binding as quantitative comparisons of microparticle capture. Mixed assays were also performed comparing binding of common MP species including polyethylene (50, 200 µm), polystyrene (10 µm), and polyester fibers (1000 µm) to understand how varying composition, size, and form factor affect adsorption. The glass slide method showed increasing linear trends of particle binding with increased adhesive exposure time and MP concentration. The lower molecular weight 92K adhesive had lower viscosity, higher wettability for microplastics but also led to a less stable adhesive film complicating analysis. As a field-deployable scheme for mi

关键词： Aggregates

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Crystallization of POSS in a PEG-Based Multiblock Polyurethane: Toward A Hybrid Hydrogel

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MRS Online Proceedings Library 2021年第1期847卷 59-64页

作者： Jian Wu Qing Ge Kelly A. Burke Patrick T. Mather Chemical Engineering Department and Polymer Program Institute of Materials Science University of Connecticut Storrs USA Department of Macromolecular Science and Engineering Case Western Reserve University Cleveland USA

Building upon earlier success in forming materials with crystalline ordering of POSS via the telechelic architecture with POSS end-capping polyethylene glycols, here we report similar ordering in PEG-POSS thermoplastic polyurethane applicable to a novel hybrid hydrogel. Thus, a unique series of hybrid thermoplastic polyurethanes (TPUs) were synthesized using poly(ethylene glycol) (PEG) as soft segment and incorporating an isobutyl-functionalized POSS diol (TMP POSS diol) in the hard segment. The molecular weight of PEG was systematically varied to include 10, 20, and 35 kDa while the mole ratio of PEG to POSS diol (as chain extender) was chosen as 8:1. The diisocyanate employed for TPU polymerization was 4, 4'-methylenebis(phenyl-isocyanate) (MDI). Wide-angle X-ray diffraction (WAXD) studies revealed that both the hydrophilic soft segments (PEG) and hydrophobic hard segments (POSS) can form crystalline structures driven by micro-phase separation, itself due to thermodynamic incompatibility. Differential scanning calorimetry (DSC) and rheological studies revealed that thermal history is important in controlling the crystallization of a POSS-rich nanophase. Increasing the cooling rate monotonically decreases the crystallinity of POSS-rich phase and results in a decrease in the ultimate dynamic storage modulus following POSS crystallization and an increase of the loss angle for temperatures above Tm of PEG and below Tm of POSS. We conclude that both composition and thermal history are key factors in determing the internal network built by the POSS nanophase, which will have a significant influence on the properties of the resulting hybrid hydrogels now being studied.

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Photoresponse Characteristics of Archetypal Metal-Organic Frameworks (vol 116, pg 3112, 2012)

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JOURNAL OF PHYSICAL CHEMISTRY C 2012年第15期116卷 8858-8858页

作者： Feldblyum, Jeremy I. Keenan, Elizabeth A. Matzger, Adam J. Maldonado, Stephen Macromolecular Science and Engineering University of Michigan Ann Arbor MI 48109-2136 2300 Hayward Avenue United States Department of Chemistry University of Michigan Ann Arbor MI 48109-1055 930 North University United States Program in Applied Physics University of Michigan Ann Arbor MI 48109-1040 450 Church Street United States

The photoelectrochemical responses of two archetypal metal–organic frameworks (MOFs), MOF-5 and MOF-177, have been assessed. Films of MOF-5 and MOF-177 were grown on carboxylic-acid-terminated conductive fluorine-doped tin oxide substrates. Separate analyses by powder X-ray diffraction, Raman spectroscopy, and fluorescence spectroscopy collectively indicated these films prepared via a solvothermal method in diethylformamide were free of residual impurities such as ZnO clusters and residual organics. Exposure of these films to white light illumination while immersed in acetonitrile electrolytes elicited measurable photocurrents. Wavelength-dependent analysis of the photoresponses showed that the measured photocurrents were induced by ultraviolet light and that the spectral response profiles followed closely the light absorption profiles of each respective material. Attenuation of the induced photocurrents was noted after prolonged ultraviolet light illumination and/or exposure of the films to H2O(l), indicating that the observed photoresponse properties are directly related to the structural integrity of these MOFs. The cumulative data illustrate that such MOFs have innately light-sensitive properties that are atypical in high surface area materials.

关键词： Photonics Photoresponse Metal organic frameworks Quantum mechanics Materials

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Dispersion of cobalt ferrite functionalized graphene nanoplatelets in PLA for EMI shielding applications 36

Dispersion of cobalt ferrite functionalized graphene nanopla...

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36th Technical Conference of the American Society for Composites 2021: Composites Ingenuity Taking on Challenges in Environment-Energy-Economy, ASC 2021

作者： Anurakparadorn, Kanat Taub, Alan Michielssen, Eric Department of Materials Science and Engineering Macromolecular Science and Engineering Program University of Michigan 2300 Hayward St Ann ArborMI48109 United States Department of Mechanical Engineering University of Michigan 2350 Hayward St Ann ArborMI48109 United States Department of Electrical Engineering and Computer Science University of Michigan 1310 Beal Ave Ann ArborMI48109 United States

ISBN: (纸本)9781713837596

The proliferation of wireless technology calls for the development of cost-effective Electromagnetic Interference (EMI) shielding materials that reduce the susceptibility of high-speed electronic circuits to undesired incoming radiation. Ideally, such materials offer protection over wide frequency ranges and are insensitive to the polarization or angle of incidence of the impinging fields. Here, next-generation EMI shielding materials composed of polymer composites with conductive and magnetic fillers are introduced. It is shown that careful control of the concentration and dispersion of the polymers’ conductive and magnetic constituents permits tuning of the composites’ intrinsic electrical and magnetic properties. The resulting EMI shields are lightweight, cheap and offer greater protection than traditional metal gaskets and foams. In this work, cobalt ferrite magnetic nanoparticles (CoFe2O4) decorated on graphene-based material were dispersed in polylactic acid (PLA) matrix for high EM absorption level in X-band (8-12 GHz). The decoration of the magnetic particles was performed on the as-prepared conductive graphene nanoplatelets (GNP) and reduced graphene oxide (rGO). GNP composites exhibited higher DC conductivity, and permittivity than rGO composites. This is attributed to issues associated with the reduction process, including a lack of conductivity due to the insulated oxygen functional groups and the reduction in the lateral size. Compared with rGOs, the lack of out-plane functional groups causes the cobalt ferrite nanoparticles to agglomerate and not cover the entire surface of the GNPs. These morphological differences improve the magnetization and EM absorption of the composite system. The compatibilizer (pyrene-PLA-OH) was added to the composites to enhance dispersion of the GNPs in the polymer matrix which benefits in higher absorption of the shield. The influence of the compatibilizer on parameter, the reflection loss (RL) of the composite were determi

关键词： Cost effectiveness

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