DIFFUSION DYNAMICS OF HAIRY-ROD POLYMERS IN CONCENTRATED-SOLUTIONS

Photon correlation spectroscopy was employed in the polarized geometry in order to investigate the dynamics of solutions of substituted poly (p-phenylenes) at high concentrations. The total concentration fluctua tions were found to exhibit a two-step decay. The fast dominant relaxa tion was the classical cooperative diffusion, controlled by the osmoti c pressure of the system, exhibiting a stronger concentration dependen ce compared to flexible polymers, and discussed in the framework of th e wormlike model. On the other hand, the second diffusive process was not related to self-diffusion (as confirmed by independent pulsed fiel d gradient NMR measurements) and could not be accounted for by the exi sting theories. The self-friction coefficient was found to exhibit a s tronger concentration dependence than the cooperative friction coeffic ient. At high concentrations, a diffusive cluster process was detected , despite the high solubility of these polymers in different solvents. The characteristics of this mode depended strongly on the molecular w eight.