High molecular weight polystyrene fractions

The following intrinsic viscosity values of some high molecular weight polystyrene fractions have been reportedf ... 

Janca, J. Martin, M. Influence of operational parameters on retention of ultra-high molecular weight polystyrenes in thermal field-flow fractionation. Chromatographia 1992,34,125. Semyonov, S.N. Kuznetsov, A. A. Zolotaryov, P.P. Theoretical examination of focusing field-flow ftactionation. J. Chromatogr. 1986, 364, 389. 

Field flow techniques have been reviewed in a number of articles [148-150]. Sedimentation field flow fractionation has found use in the separation of PVC [151, 152], polystyrene [151-153], poly(methyl methacrylate) [153, 154], poly (vinyl toluene) [155] and poly(glycidyl methacrylate) latexes [156] to produce particle-size distributions and particle densities. It has also been applied in polymer-aggregation studies [157], pigment [157] quality control and in the separation of silica particles [158] and its performance has been compared with that of ultracentrifugation [159]. Thermal field flow fractionation has been used successfully in the characterisation of ultra-high-molecular-weight polystyrenes [160, 161], poly(methyl methacrylate), polyisoprene, polysulphane, polycarbonate, nitrocellulose, polybutadiene and polyolefins [162]. In the difficult area of water-soluble polymers, poly(ethylene glycol), poly(ethylene oxide), poly(vinyl pyrrolidone) and poly(styrene sulphonate) have been analysed [163, 164]. In addition, compositional separations have been achieved for polystyrene-poly(methyl methacrylate) mixes [165] and comparisons between TFFF and SEC have been made [166]. 

Typical results of lightscattering measurements are shown in Figs. 47 and 48 for polystyrene fractions of medium and of very high molecular weight, respectively. The small dissymmetry correction for the former was calculated from the measured dissymmetry coefficient 45°( l-2) using Eqs. (31) and (32). 

Like SEC/LALLS, the viscosity detector is sensitive to high molecular weight fractions as shown in Fig, 7. A shoulder at 3,000,000 molecular weight detected by the DRI becomes a peak when detected by the viscometer detector. The usefulness of the SEC/Viscometer method is exemplified by the study of branched polymers. Fig. 8 shows a log [ ] vs. log M plot for a randomly branched polystyrene obtained from the SEC/ iscometer technique. 

Fig. 5.1. Flow birefringence An vs. shear rate q for solutions of a polystyrene fraction of high molecular weight (ikf = 1.7 X 10 ) in dioxane according to Frisman and Syto Mao (139). Concentrations in g/100 cm3 are given near the curves...

Fig. 5.9. Comparison of extinction angle curves of high molecular weight fractions of polystyrene and cellulose tricarbanilate, using linear scales and reduced shear rate For data on polystyrene Taps. No. 5 and solvents see Table 3.2. (n) Taps. No. 5 in methyl (4-bromo-phenyl carbinol) at 18° C (theta-temperature), (V) the same at 50° C, (o) Taps. No. 5 in monobromo benzene at 25° C, ( ) cellulose tricarbanilate M = 720,000 in benzophenone at 55° C (jy = 4.70 cps) and (a) at...

Very recently, Gramain and Myard84 investigated the effect of the shear rate on LH, using high molecular weight fractions of polyacrylamide and polystyrene. Polyacrylamide was hydrolyzed to various degrees. Five commercial filters of pore radii from 1.5 to 6 fim were used as porous media. Measurements were carried out on polyacrylamide in water and polystyrene in toluene. 

A semidilute solution [42] of high molecular weight deuterated polystyrene (Mw = 1.95 x 106 g/mole, Mw/M = 1.64) in dioctyl phthalate (DOP) at a volume fraction of 2.83% of polystyrene was measured by SANS at room temperature. A characteristic intensity behavior I(Q) was obtained after data correction (solvent incoherent scattering, empty cell scattering and usual background corrections, etc.) and was circularly averaged. The reduced I(Q) data was then fitted to the following form ... 

As already noted, the measured nonlinear shear relaxation modulus, for linear molecules with little polydispersity, is in excellent agreement with the Doi-Edwards model at long times. However, for melts or concentrated solutions of very high molecular weight (e.g., 10 for polystyrene, where 0 is the polymer volume fraction), the measuredfiamping function, h(y), is drastically lower than the Doi-Edwards prediction (Einaga et al. 1971 Vrentas and Graessley 1982 Larson etal. 1988 Morrison and Larson 1992). This anomalous... 

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