SELF-DIFFUSION COEFFICIENT STUDIES IN POLYSTYRENE POLYSTYRENE/TOLUENESOLUTIONS - DYNAMIC LIGHT-SCATTERING AND FLUORESCENCE RECOVERY AFTER PHOTOBLEACHING EXPERIMENTS/

The dynamical behavior of a polystyrene(M-w1)/polystyrene(M-w2)/toluen e ternary mixture has been investigated by Dynamic Light Scattering (D LS) and Fluorescence Recovery After Photobleaching (FRAP). The experim ents were made at several total polymer concentrations C-T from dilute to semi-dilute range of concentration. In FRAP experiments, the dynam ic of such a system is characterized by the existence of one relaxatio n mode identified to the self-diffusion coefficient D-s of the labelle d polymer. This mode has been compared to the corresponding extracted D-s value from the two relaxation modes observed in DLS. The compariso n between the results shows that in the semi-dilute range of concentra tion the agreement is good between both D-s values. As the concentrati on decreases, the agreement becomes less and less satisfactory, showin g the limitation of the theory used to extract D-s from DLS measuremen ts to the semi-dilute regime.