Poly copolymers relaxation times

Homopolymers and copolymers made from 3-vinylpyridinium salts form compact coils in solution media" while different isomers of dimethylamino-stilbazolium dyes exhibit different emitting states with a temperature dependent population." Using fluorescence depolarisation the relaxation time of poly-(styrene) chains has been found to decrease with expansion of the chain coils." " ... 

Effects of addition of a compatibilizing block copolymer, poly(styrene-b-methyl methacrylate), P(S-b-MMA) on the rheological behavior of an immiscible blend of PS with SAN were studied by dynamic mechanical spectroscopy [Gleisner et al., 1994]. Upon addition of the compatibilizer, the average diameter of PS particles decreased from d = 400 to 120 nm. The data were analyzed using weighted relaxation-time spectra. A modified emulsion model, originally proposed by Choi and Schowalter [1975], made it possible to correlate the particle size and the interfacial tension coefficient with the compatibilizer concentration. It was reported that the particle size reduction and the reduction of occur at different block-copolymer concentrations. 

Spin diffusion measurements of poly(phthalainide)/poly(diniethylsiloxane) block copolymers having separated phases (rigid poly(phthalamide) part, mobile PDMS part) showed different domain sizes depending on the length of the PDMS chain. The shorter the chain, the smaller is the domain size of the separated PDMS phase. To determine the spin diffusion coefficient of the mobile phase spin-spin, relaxation time T2 was measured. It showed the big mobility difference between the sample with the short chain (PAioPDMSn) and the other two samples (PA10PDMS50 and PAioPDMSioo) — one order of magnitude. Therefore, the PDMS chain with 11 links is fairly restricted in its mobility compared with the other two chains with 50 and 100 links. 

A random copolymer based on poly(L-lactide) with poly(E-caprolactone) was prepared and characterized by mechanical testing and solid state NMR, compared with a polymer blends, this was studied by using the relaxation times. Tic and Tip. ... 

VanderHart et al. (2001a-c) studied different clay nanocomposites measuring clay exfoliation by relaxation times of hydrogen that sees iron in the montmorillonite clay. They used Fe atoms in montmorillonite clay to determine clay dispersion in Nylon-6 matrix, and degraded alkyl ammoniums (from thermal processing above 200 C) were observed by NMR technique. Hou et al. (2002,2003) studied clay intercalation of poly(styrene-ethylene oxide)-b/ocfe-copolymers using multinuclear solid-state NMR. Hrobarikova et al. (2004) prepared polycaprolactone with laponite or saponite nanocomposites by in sitn polymerization and characterized by CAP NMR to understand how surfactants at clay surface interacted with polymer matrix. Hrobarikova et al. (2004) used solid-state NMR to study intercalated species in poly(e-caprolactone)/clay nanocomposites. 

Figure 42 Concentration dependence of the terminal modulus calculated from steady shear relaxation time (filled symbols) and from the oscillatory shear relaxation time (open symbols) at 25 °C in ethylene glycol solvent of random copolymer 2-vinyl pyridine and /V-methyl-2-vinyl pyridinium chloride (PMVP-CI) with various charge densities (numbers in the legend correspond to the extent (mol.%) of quaternization) and the uncharged neutral parent poly(2-vinyl pyridine) (P2VP) of 44=364 000 Da (open circles). Data provided by Dou, S. Colby, R. H.

Two-component systems have received some attention. - Poly(vinyl-idene fluoride>-poly(methyl or ethyl methacrylate)s blends have been mentioned in the previous section. A study of compatibility in blends of poly(vinyl chloride) and ethylene-vinyl acetate copolymer (EVA) has been reported. Spin-lattice relaxation time measurements were bi-exponential corresponding to rigid [poly(vinyl chloride)] and mobile (EVA) phases. A precipitated mixture showed intermingling of EVA in the poly(vinyl chloride) phase, but phase separation occurred on heating. Cashell et a/. have contributed a short note on the effects of magnetic susceptibility inhomogeneities of lincwidths in carbon black-filled... 

The characteristic relaxation times obtained by the HN fit to the data, after conversion to Tnjax (Equation 20.3), are plotted versus the inverse of temperature in Figure 20.15 for poly(ATRIF) homopolymer and poly(AN-co-ATRIF) copolymer. 

FIGURE 20.15 Temperature dependence of the relaxation times of both poly(ATRIF) homopolymer (squares) and poly(AN- faf-ATRIF) copolymer (circles) the arrows indicate the glass transition temperatures estimated from the VFTH equations at x = 100 s [68],... 

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