Dielectric Normal Mode Relaxation of Poly(propylene oxide) and Poly(butylene oxide) in Dilute and Semidilute Solutions.

We investigated the dielectric normal mode relaxation in dilute and semidilute solutions of poly(propylene oxide)(PPO) and poly(butylene oxide)(PBO) in benzene which is a good solvent for PPO but a marginal solvent for PBO. The results indicate that the normal mode relaxation times τ_n in dilute solutions of PPO and PBO are proportional to [η]M in agreement with the Rouse-Zimm theory where [η] and M denotes the intrinsic viscosity and the molecular weight, respectively. With increasing concentration C, τ_n increases in proportion to C[η]. The dynamic crossover concentration between the dilute and semidilute regimes is about four times higher than the static crossover concentration C^*. The relaxation strength Δε divided by C decreases with increasing concentration indicating that the mean square end-to-end distance (r²) decreases on account of the screening of the excluded volume effect. The concentration dependence of (r²) agrees approximately with the scaling theory. [ABSTRACT FROM AUTHOR]