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Interface characteristics of polystyrene (PS) melts in free-standing thin films and on a graphite surface were investigated by molecular dynamics simulations employing an explicit all-atom force field. The calculated surface tension is in good agreement with experiment, which provides good support for the force field parameters employed. In the polymer/vacuum free-surface region, the density profile...
Cholesterol self-assembles into weakly ordered aggregates when tethered to a crosslinked hydrogel network of poly(ethylene glycol) (PEG). PEG-diacrylate and cholesterol-PEG-acrylamide (PEG-chol) were co-polymerized in organic solvent and transferred to water for equilibrium swelling. Small-angle x-ray scattering revealed self-assembled cholesterol structures not present during network synthesis. At...
A class of tunable, mesostructured self-assembled hydrogels has been developed based on a library of π–π stacking ABA-type telechelic triblock copolymers prepared by organocatalytic ring-opening polymerization (ROP). Poly(ethylene glycol) (PEG) served as a macroinitiator for ROP of methylene tricarbonate-benzyl ester (MTC-OBn), a benzyl-ester functionalized cyclic carbonate monomer, resulting in polymers...
A small molecule nucleating agent, orotic acid (OA), was investigated to enhance crystallinity and crystallization kinetics in poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) for the purpose of addressing embrittlement and reducing solidification time after thermal processing. In particular, the effectiveness of monohydrated (OA-m) and anhydrous (OA-a) forms of OA as nucleating agents for isothermal...
The governing kinetic behavior of water transport in a biopolymeric composite material derived from poly(β-hydroxybutyrate)-co-poly(β-hydroxyvalerate) and lignocellulosic wood flour were investigated along with the influence of temperature, wood flour content, and chemical modification (silane, maleic anhydride) on polymer and composite diffusivity. The water absorption process in both untreated and...
Films of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB-co-3HHx) containing 3.8–10 mol% of 3-hydroxyhexanoate (3HHx) comonomer were subjected to anaerobic biodegradation to explore the effects of copolymer composition, crystallinity, and morphology on biodegradation. As biodegradation proceeded, samples with higher HHx fraction tended to have faster weight loss; on Day 7 of the degradation experiment,...
Diffusion coefficients of small oligosaccharides within high strength poly(ethylene glycol)/poly(acrylic acid) interpenetrating network (PEG/PAA IPN) hydrogels were measured by diffusion through hydrogel slabs. The ability of hindered diffusion models previously presented in the literature to fit the experimental data is examined. A model based solely on effects due to hydrodynamics is compared to...
The rheological properties of a series of microbially synthesized poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)s (PHB-HHxs), with varying comonomer (HHx) content, were systematically investigated. Shear viscosities show dependence on the rate of deformation, temperature, molecular weight, and copolymer compositions. The zero-shear viscosity η 0 follows the classical Mw3.4 power-law relationship...
In this paper, we present the systematic development of mechanically enhanced interpenetrating polymer network (IPN) hydrogels with Young's moduli rivaling those of natural load-bearing tissues. The IPNs were formed by synthesis of a crosslinked poly(acrylic acid) (PAA) network within an end-linked poly(ethylene glycol) (PEG) macromonomer network. The strain-hardening behavior of these PEG/PAA IPNs...
The composition of semi-interpenetrating polymer networks (semi-IPNs) based on responsive N-isopropylacrylamide (NIPAAm) hydrogels has been shown to affect the kinetics of the volume phase transition. Several N-alkyl-substituted acrylamides were used as the linear polymers in a crosslinked NIPAAm network, and the kinetics was observed as a function of crosslinking density and linear polymer concentration...
We have evaluated the potential use of thermoresponsive hydrogels based on N-isopropylacrylamide as actuators in microfluidic and lab-on-a-chip devices. This required fabrication of hydrogel actuators on the μm length scale, anisotropic swelling of the resulting materials, and control over the kinetics of the hydrogel volume phase transition. The fabrication procedure combined gel polymerization and...
We have evaluated the mechanical strength of a series of composites consisting of carbon particles bound together by poly(vinylidene fluoride) (PVDF), which is closely related to the carbonaceous anode in a lithium ion battery. We used a balanced beam scrape adhesion tester and evaluated the influence of carbon particle structure, the chemical properties of PVDF, and the processing parameters of annealing...
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