DETERMINATION OF CHAIN CONFORMATION OF STIFF POLYMERS BY DEPOLARIZED RAYLEIGH-SCATTERING IN SOLUTION

The chain conformation of a series of polydisperse polyesters and poly (p-phenylenes) has been investigated by means of depolarized Rayleigh scattering in solution. By considering polydisperse worm-like chains, using a Schultz-Zimm distribution, the persistence length, q, was dete rmined from the specific depolarized Rayleigh ratio at infinite diluti on and the weight average chain contour length, without involving opti cal anisotropies or the internal field problem. This general analysis showed that the effect of polymer nonuniformity is nearly negligible. For the polyester, q was found to be approximately 19 nm, whereas for the poly(p-phenylene) it was about 28 nm; these values exhibit the cor rect trend, but are higher than the corresponding ones from other tech niques. Deviations are mainly attributed to the limited range of molec ular weights available; this restricts the polyesters near the coil li mit and the poly(p-phenylenes) near the rod Limit. Using optical aniso tropy data of the monomers and Various oligomers, the validity of Flor y's addivity scheme is verified for these systems.