INTERNAL STRUCTURE AND DYNAMICS OF DILUTE LINEAR-POLYMERS

We report measurements of the internal structure and dynamics of a dilute high molecular weight polymer in good and 0 solvents, with a special emphasis on the form of the decay of internal modes. Intermediate elastic light scattering measurements show that the static structure exhibits the expected self-avoiding walk and random-walk fractal dimensions in good and theta-solvents, respectively. Quasielastic light scattering studies of the relaxation of internal "Zimm" modes demonstrate the universal q3 dependence of the initial decay rate on the scattering wavevector. However, the primary goal of this work, to observe the expected stretched exponential time decay exp[-(t/tau)b] with the Zimm exponent b = 2/3, was difficult to achieve, even though we used the lambda = 331.6 nm UV line of an argon ion laser to monitor relaxations on length scales much smaller than the polymer radius. In a good solvent we obtained b congruent-to 0.72, and in a theta-solvent we obtained b congruent-to 0.71. We compare these results to extant experimental and theoretical work.