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Quasielastic light scattering studies on diffusion and interaction of polymers in solutions
Abstract
The dynamic behavior of the mixture polymer-1/polymer-2/solvent was studied by quasielastic light scattering. Theoretically, based on random phase approximation, we have proposed a new method that allows one to obtain the self-diffusion coefficients of the homopolymers and the polymer-polymer interaction parameter in the ternary polymer solution from the quasielastic light scattering experiment. The method removes stringent conditions previously imposed on the polymer systems to utilize the theory and is useful for ternary polymer solutions consisting of homopolymers with arbitrary molecular weights and solvent interactions. The method has been used to study different ternary systems, such as PS/PMMA/benzene, where PMMA is isorefractive with benzene, PS-1/PS-2/toluene, where PS-1 and PS-2 are only different in molecular weight, and arbitrary ternary systems PS/PMMA/dioxane and PS/PIP/chloroform. The results obtained from those studies indicate that the self-diffusion coefficients of two polymers depend on total polymer concentration and polymer composition, but the polymerpolymer interaction parameter has a weak concentration and composition dependencies. The effect of an applied electric field(E-field) on the dynamics of polystyrene (PS) in tetrahydrofuran (THF) was also studied by quasielastic light scattering. The concentration of the PS/THF solution was varied from very dilute to semidilute, and the applied E-field was up to 714V/mm. In the dilute regime, the relaxation rate of PS increases sharply with the increase of applied E-field, and the effect magnitude of E-field on the dynamics of PS in THF is nearly constant in the dilute regime. However, in the semidilute regime, the applied E-field has little effect on the dynamics of PS in PS/THF solution. The above results confirm that the electrorheological (ER) effect and the change in free energy due to the applied E-field are not factors in the effect of the E-field on the dynamics of PS in PS/THF. From our study, the induced current, which is due to the conductive electrodes used in our and previous experiments, can account for the effect of E-field on the dynamics of PS in THF.
Subject Area
Polymers
Recommended Citation
Sun, Zhenhua, "Quasielastic light scattering studies on diffusion and interaction of polymers in solutions" (1999). ETD collection for University of Nebraska-Lincoln. AAI9929236.
https://digitalcommons.unl.edu/dissertations/AAI9929236