Light scattering from dilute polystyrene in mixtures of semidilute poly(dimethylsiloxane) and tetrahydrofuran

Abstract

Ternary solutions of tetrahydrofuran (THF), polystyrene (PS), and poly(dimethylsiloxane) (PDMS) were studied using total low-angle light scattering and dynamic light scattering. The PS concentration, c2, was varied but was always kept very dilute. The PDMS concentration was held constant at the semidilute concentration of 15 vol %, corresponding to 3c3*, where c3* is the entanglement concentration. The range of PS molecular weights investigated was such that Rh.z/Ís' where RH 2 is the hydrodynamic radius of PS in pure THF and f3 is the dynamic correlation length of the semidilute PDMS matrix, fell in the "crossover" regime between 0.7 and 3.0. The tracer diffusion coefficient of PS at infinite dilution, D22(0), was determined from the "measured" mutual diffusion coefficient, X2(c2), according to X2(c2) = D22(0)(1 + kBc2). D22(0) in the examined system scales with molecular weight according to D22(0) ~Mw2~°m. Similar to a binary mixture, we show that kO defined above may be represented by two terms, one arising from thermodynamic interactions and the other from hydrodynamic interactions. The dependence of kO on molecular weight is found to be kD--A/w20"57 and is dominated here by the thermodynamic term.

Quasielastic Light Scattering from Semidilute Ternary Polymer Solutions of Polystyrene and Poly(methyl methacrylate) in Benzene

“…Under such a condition, the interdiffusion coefficient is approximately equal to the self-diffusion coefficient of the visible polymer. By using this method, a number of researchers have investigated the dynamics of the visible polymer chain in the ternary solutions, [15][16][17][18][19][20][21] with the objective to test whether the dynamics of single chains assumes the Rouse-like or a reptation mechanism. 22 QEL scattering experiments from semidilute ternary polymer solutions have also recently been carried out.…”

Dynamic light scattering experiments on poly(vinyl methyl ether) (PVME)-polystyrene-toluene and PVME-polystyrene-carbon tetrachloride solutions

“…The second theory of dynamic light scattering from ternary polymer solutions was developed by Cohen et al18,19 This theory assumes that the majority polymer has no contrast with the solvent, and it further assumes that the concentration of the visible polymer is low and the solution is semidilute. There is no restriction on solvent quality.…”

Static and dynamic light scattering from multicomponent polymer mixtures PS/PDMS/PMMA/toluene

“…These dynamical models are well documented in the literature [3,5,11,17, 181 and they are not discussed in more detail here because the analysis of the data considered in this work does not require such a level of sophistication. Various investigations by quasi-elastic light scattering [12][13][14][15][16], including the one reported in [l], indicate that the long range hydrodynamic interactions between different chains are substantially reduced and Rouse-like behavior prevails. However, results for the single chain properties, and in particular for the selfdiffusion coefficient 0, exploring different molecular weights of the polymers, indicate that the dynamics within chains is characteristic of the Zimm model, meaning that the intramolecular hydrodynamic interactions remain important.…”