DIELECTRIC NORMAL-MODE RELAXATION OF POLY(LACTONE)S IN SOLUTION

We studied the dielectric normal mode relaxation in dilute and semidil ute solutions of poly(epsilon-caprolactone) (PCL) and poly(delta-valer olactone) (PVL) in benzene using narrow distribution samples prepared with an initiator of a lanthanoid complex. The effect of long nonpolar groups separating the polar ester groups on the dielectric behavior w as investigated by comparing the present results with those for cis-po lyisoprene (PI) solutions reported previously. In dilute solutions, th e longest relaxation time tau for both PCL and PVL increased in propor tion to M(1.63+/-0.03) . Th, double-logarithmic plots of tau vs [eta]e ta(s)M/RT for the dilute solutions as well as those of PI fell on the same universal straight Line irrespective of the solvent quality. Here [eta] and eta(s) are the intrinsic viscosity and the solvent viscosit y, respectively. The, dielectric loss factor epsilon'' vs frequency f curves for the dilute PCL and PVL solutions agreed with the Zimm theor y. In the semidilute solutions, log tau increased linearly with respec t to C as predicted by the Muthukumar-Freed theory. The epsilon'' curv e broadened with C as observed previously for PI semidilute solutions. The dynamical behavior is independent of the local structure. The die lectric relaxation strength Delta epsilon, which is proportional to th e mean square end-to-end distance (r(2)), increased with M in dilute s olution but decreased with C above the overlap concentration.