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Several different solvent systems are commonly used to dissolve Bombyx mori silk fibroin to prepare regenerated silk membranes and fibers though differences in the behavior of these solvents have not been fully investigated. Here we compare the effects of four of these on the rheology of silk fibroin solutions and on protein secondary structure as revealed by FTIR spectroscopy of cast membranes. The...
Syndiotactic polystyrene/modified-clay nanocomposites have been prepared by solution blending by mixing pure s-PS and organophilic clay with adsorbed cetyl pyridium chloride (CPC) in dichlorobenzene. The dispersability of the clay in syndiotactic polystyrene/modified-clay nanocomposites was studied using X-ray and transmission electron microscopy. The clay is well dispersed into the s-PS matrix using...
Two topics relating to banded polymer spherulites are discussed thoroughly and brought up to date. They are: (a) origins of secondary effects of rhythmic character in thin films and (b) generation of isochiral dislocations and torsions in twisted lamellae. Physical principles of broad applicability are also emphasized.
A mass spectrometric method has been used to study transmission of noble gases (He, Ne, Ar, Kr, Xe) through thin polymer membranes of OPP and PET. The transmission of gas originating from a confined volume in a gas cell through the membrane is measured by a mass spectrometer. Due to depletion of gas inside the gas cell, transmission decreases as a function of time, which is taken as a measure for...
The effect of curing conditions such as time and temperature on the morphology developed in a diglycidyl ether of bisphenol-A epoxy resin cured with diamino diphenyl methane, and modified with 15wt% poly(methyl methacrylate), has been investigated. The reacting mixtures were precured at 80 o C for a period of time ranging from 2 to 7h, afterwards they were cured at 140 o C and finally...
The reductive dechlorination of poly(vinyl chloride) (PVC) with lithium aluminium hydride, tri-n-butyl tin hydride and lithium triethyl borohydride as reducing agents has been performed in the solution of tetrahydrofuran. A comparative study of the microstructural evolution with conversion using the three different reducing agents was carried out. The quantitative microstructural analysis with conversion...
Long chain branches (LCB) were added to initially linear polypropylene (PP) using reactive extrusion in the presence of selected organic peroxydicarbonates (PODIC). The LCB structure was confirmed by high temperature size exclusion chromatography combined with on-line intrinsic viscosity measurements. Compared to the initial linear PP, the branched samples showed distinct strain hardening of the elongational...
In the electrospinning process, polymer fibers with submicron-scale diameters are formed by subjecting a fluid jet to a high electric field. We report an experimental investigation of the electrically forced jet and its instabilities. The results are interpreted within the framework of a recently developed theory for electrified fluid jets. We find that the process can be described by a small set...
Solubility and diffusivity of sodium chloride were determined in a series of dense films of phase-separated diblock and triblock copolymers composed of poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) and either poly(1,1'-dihydroperfluorooctyl methacrylate (PFOMA) or poly(1,1,2,2-tetrahydroperfluorooctyl acrylate) (PTAN). As the content of hydrophilic PDMAEMA increases in PDMAEMA-b-PFOMA films, total...
Polyethylene and other polyolefins have not been amenable to mass spectrometric characterization of molecular mass distribution due to the ineffectiveness of conventional methods of cationization. The lack of polar groups, unsaturation, and aromaticity excludes cationization methods that are used commonly for polymers. A new method is introduced in which an organic cation is covalently bonded to the...
When transition metal cations coordinate to ligands in the sidegroup of a polymer and modify the thermal response of a macromolecular complex, the enhancement in T g can be explained by focusing on ligand field stabilization of the metal d-electrons. The methodology to identify attractive coordination complexes and predict relative increases in T g is described in terms of the local...
Poly( -caprolactone)-perfluoropolyether-poly( -caprolactone) block copolymers (TXCL) synthesised from Fomblin Z-DOL TX (TX) have been mixed with conventional unsaturated polyester resins (UPR) to prepare fluorine modified UPR (FUPR). A preliminary investigation on the compatibility of uncured FUPR systems has shown that the presence of PCL blocks leads to an enhancement of compatibility with respect...
Photon transmission experiments were performed using a UV-visible (UVV) spectrometer during the swelling of polyacrylamide (PAAm) gels. These gels were prepared from acrylamide (AAm) with various N,N'-methylenebisacrylamide (Bis) contents by free-radical crosslinking copolymerization (FCC) in water and dried before use for swelling experiments. Transmitted light intensity, I tr increased...
The FT-IR spectra for three polyglutamates containing different side chains, poly(γ-methyl α, l-glutamate) (PMLG), poly(γ-hexyl α, l-glutamate) (PHLG), and poly(γ-stearyl α, l-glutamate) (PSLG), were measured and analyzed. Experimental data show that longer side chains induce weaker hydrogen bonds between the carbonyl groups and the amide linkages of the α-helical backbone. Simulated infrared spectra...
Poly(ethylene oxide) PEO/Na + -montmorillonite and polyethylene-poly(ethylene glycol) (PE-PEG) diblock copolymer/Na + -montmorillonite nanocomposites have been prepared by melt intercalation method. The effect of thermal treatment on the amount of PEO and PE-PEG diblock copolymer intercalated into layers of Na + -montmorillonite and on ionic conductivity of PEO/Na + ...
Novel copolymers carrying N-hexyl-3,8-iminodibenzyl chromophores have been synthesized by polycondenzation of N-hexyl-3,8-diformylminodibenzyl with 1,4-xylylene-bis(diethylphosphonate) via the Horner reaction (P1) or with 1,4-phenylenediacetonitrile via the Knoevenagel reaction (P2). The reduced viscosities of P1 and P2 are 1.17 and 0.43dl/g, respectively. The P2 with electron-withdrawing CN groups...
Multiple phase behavior was found in copolymer gels consisting of dimethylacrylamide and methacrylic acid. They are characterized by distinct degrees of swelling; the gel can take one of a set of swelling values, but none of the intermediate values. Three different phases, denoted as phase051 (as-prepared), phase376 (swollen at high pH), phase440 (swollen after treatment by pH 12) were clearly resolved,...
Organoclay nanocomposites based on three different molecular weight grades of nylon 6 were prepared by melt processing using a twin screw extruder. Mechanical properties, transmission electron microscopy, wide-angle X-ray diffraction, and rheological measurements were used to characterize the three types of composites. Tensile modulus and yield strength were found to increase with increasing concentration...
The aim of this work is to study the miscibility of poly(methyl acrylate)/poly(methyl methacrylate), (PMA/PMMA), sequential interpenetrating networks, (IPNs), as a function of the crosslink density using dielectric and dynamic-mechanical techniques. The PMA/PMMA system is immiscible and so, for low crosslink densities, phase separation appears, as detected by the occurrence of two clearly differentiated...
The dielectric relaxation was determined in a time-domain spectrometer between 100 and 295K and from 0.1 to 1000Hz for series of dendritic liquid crystalline polymers with scaffolds based on 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) of generations 0-3 with 4''-((R)-1-methylheptyloxy)phenyl 4-{4'-[10-(hydroxy-carbonyl)decyloxy]-phenyl} benzoate as mesogen and for the second generation of dendrimers...
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