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

Abstract

A detailed quasieslatic light (QEL) scattering study of the polystyrene-poly(methyl methacrylate) (PS-PMMA)/benzene ternary solution with both polymers in the semidilute concentration regime was carried out. Two types of the PS-PMMA/benzene solution have been studied: one at fixed composition but different total polymer concentrations, and the other at fixed total polymer concentration but different compositions. Two diffusion modes in the intensity-intensity time correlation function of the scattered light were observed in these solutions. These two modes correspond to the eigenmodes of the diffusivity matrix that governs the time evolution of the concentration fluctuations of the polymers in the ternary solution. The concentration and composition dependencies of the relaxation rates and the amplitudes of these modes were investigated. From the relaxation rates and amplitude factors, the elements of the diffusivity matrix were determined as a function of polymer concentration and composition. By using the diffusivity data, the self-diffusion coefficients of PS and PMMA and the Flory-Huggins interaction parameter F, between PS and PMMA were deduced. The concentration and composition dependencies of these quantities were studied. At fixed composition, the self-diffusion coefficients of PS and PMMA were found to decrease with increasing total polymer concentration, whereas at fixed concentration they decreased with decreasing fraction of its own kind. The value of the Flory-Huggins interaction parameter, F, between PS and PMMA was found to range from 0.008 to 0.026, depending on concentration and composition. The F values obtained by our method are in good agreement with those obtained by other techniques, indicating the reliability of our method.

Light Scattering Studies on Ternary Polymer Blend Solutions Comprising Poly(hydroxybutyrate)

“…The inequality of Equation (17) reveals that the interpenetration function for PEO/PHB decreases as compared to the perfect system, i.e. interpenetration of the chains increases.…”

“…The opposite conclusion can be drawn for the PCL/PHB blends. Moreover, we can formulate a completely analogous inequality as in (17) for the coil volume. The corresponding quantity is always negative for the blends under discussion as Figure 3 shows:…”

“…[12][13][14][15][16][17][18][19] Light scattering data yield the second virial coefficient. In the Flory-Huggins approximation, the second virial coefficient for polymer blend solutions can be represented by an additivity term and an excess term with respect to blend composition.…”

Quasielastic Light Scattering Study of Self-Diffusion and Interaction of Two Homopolymers in an Arbitrary Solvent

“…For example, most of the early work dealt mainly with one polymer as a tracer in a polymer of high concentration which is refractive index matched to the solvent. The object in those studies was to test the reptation model by probing the self- (or tracer) diffusion coefficient of the dilute polymer which is not refractive index matched. − Recently, more experimental work has been carried out on polymer solutions in the semidilute and concentrated regimes; however, most experiments have utilized the condition that one polymer is isorefractive with the solvent to simplify data analysis. − …”

“…In actual cases, this assumption may not be valid. Recently, we have proposed a method to obtain these important quantities without the need for making this assumtion. ,, When applied to the ternary solution having one polymer isorefractive with the solvent, such as PDMS/PMMA/toluene and PS/PMMA/benzene solutions, , our method allows one to obtain the elements of the diffusivity matrix without needing the RPA. Therefore, our method, which removes the assumption introduced by Desbrieres et al, is general and more versatile.…”