QUASI-ELASTIC LIGHT-SCATTERING INVESTIGATION OF CONCENTRATION FLUCTUATIONS AND COUPLING TO STRESS-RELAXATION IN A POLYMER-SOLUTION - POLYSTYRENE IN CCL4

A detailed light scattering study of the polystyrene (PS) in carbon tetrachloride (CCl4) solution at various scattering angles and PS concentrations has been carried out. Both static and dynamic light scattering measurements have been made on the solution covering dilute, semidilute, and concentrated concentration regimes. The dynamic light scattering measurement spans a time scale of 10(-6)-10(2) s. The static light scattering measurement provides osmotic modulus and static correlation length data at various PS concentrations. The homodyne intensity-intensity time correlation function is single exponential in the dilute concentration regime, but it deviates from single exponential in the semidilute and concentrated concentration regimes. The deviation is interpreted as due to the coupling of the concentration fluctuation to longitudinal stress relaxation modes. With the help of a theory, recently developed in this laboratory, information concerning the cooperative diffusion coefficient, longitudinal stress modulus, the distribution of stress relaxation times, dynamic correlation length, and friction coefficient associated with the concentration fluctuation is obtained as a function of PS concentration. Much of the experimental data for the PS/CCl4 system is new.