Polystyrene concentration regimes

Confocal Raman microspectroscopy was used to measure local compositions along a direction that was perpendicular to the original interface. Composition profiles generated by interdiffusion in the concentrated regime between polyphenylene oxide-polystyrene blend pairs were determined (128). 

Composition profiles generated by interdiffusion in the concentrated regime between polyphenylene oxide-polystyrene blend pairs were experimentally determined by two techniques. Three-point bending moment measurements over a convenient temperature range (dynamic mechanical analysis (DMA)) were used to determine interphase composition profiles. Confocal micro-Raman spectroscopy was also used to measure local compositions along a direction which was perpendicular to the original interface. The study included some limiting cases to test accuracy, precision and flexibility of the DMA method. 4 refs. 

The existence of different concentration regimes in semidilute polyelectrolyte solutions was confirmed by the experiments of Essafl et al. on partially sulfonated polystyrene sulfonate in water. It was reported by Essafi that the exponent of the... 

Investigation of the force profile between two surfaces covered by adsorbed polystyrene brushes [57] showed that the profile can be described by Eq. (68), obtained for a semidilute concentration regime [57] ... 

N. Nemoto, T. Kojima, T. Inoue, and M. Kurata. Self-diffusion of polymers in the concentrated regime I. Temperature dependence of the self-diffusion coefficient and the steady viscosity of polystyrene in dibutyl phthalate. Polym. /., 20 (1988), 875-881. 

Another range of matrix molecule sizes P=88-3173 was used in our study [251] on PI (polyisoprene, NA=114)-dPS (N=893) diblock copolymer segregating to interfaces created by polystyrene P-mer with vacuum and silicon substrate. The used PS molecular weights covers the wet and dry brush regime. In Fig. 40a we present typical composition-depth profiles of Pl-dPS obtained at the vacuum ( external ) interface of PS host matrix with P varied (P=88,495, and 3173), but constant bulk diblock concentration < )00=3.2(5)%. The surface peak and a related surface excess z (and coverage a) increases with P. This is even... 

Experimental data were obtained for solutions with polymer concentrations varying from w = 0.50% to w = 4.00% or, equivalently, from c = 0.00431 to c = 0.0348 g cm to be compared with the estimated overlap concentration c = 0.0274 g cm-3 [22]. Hence, the experimental results correspond to polystyrene-toluene solutions in the dilute and semidilute solution regime. 

Since D in the semi-dilute regime does not depend on M, its concentration dependence for monodisperse polymers and that for their blends should become coincident in this regime. Recent work of Nemoto et al. [39] on polystyrene in benzene confirmed the prediction. In fact, their Dc data for monodisperse and binary blended samples fell on a single line with slope 0.67 on a log-log graph. This slope value agrees with that obtained by Adam and Delsanti [38] for monodisperse samples. 

Let us start with single coils at the 0 point, with a radius / = and an internal concentration d>c [eq. (IV. 14)] let us then increase the concentration d>. When 4> becomes higher than c (but still smaller than 1), the coils overlap, and we reach a well-defined semi-dilute regime, which differs strongly from the semi-dilute regime in good solvents discussed in Chapter III. Neutron data on the system polystyrene-cyclohexane near T =... 

The semidilute regime is often specified by c c< c. With c at around 10 g/L for polystyrene of = 6 X 10 g/mol, for instance, and c at around 300 g/L, the double inequality may appear to impose a severe restriction on the accessibility by an ordinary polymer. In practice, however, solutions several times as concentrated as c already qualify as semidilute solutions. With ambiguity in the definition of c (Eqs. 1.108-1.110), it does not make sense to ask how high the concentration should be for the solution to be semidilute. As we will see in many experimental results, there is an easy way to find whether or not the concentration is sufficiently high. 

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