Dielectric Normal Mode Relaxation of Poly(lactone)s in Solution

Abstract

We studied the dielectric normal mode relaxation in dilute and semidilute solutions of poly-(e-caprolactone) (PCL) and poly(d-valerolactone) (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 was investigated by comparing the present results with those for cis-polyisoprene (PI) solutions reported previously. In dilute solutions, the longest relaxation time r for both PCL and PVL increased in proportion to AfL63±0•03. The double-logarithmic plots of r vs fytysM/RT for the dilute solutions as well as those of PI fell on the same universal straight line irrespective of the solvent quality. Here [ ] and 3 are the intrinsic viscosity and the solvent viscosity, respectively. The dielectric loss factor e" vs frequency f curves for the dilute PCL and PVL solutions agreed with the Zimm theory. In the semidilute solutions, log increased linearly with respect to C as predicted by the Muthukumar-Freed theory. The e" curve broadened with C as observed previously for PI semidilute solutions. The dynamical behavior is independent of the local structure. The dielectric relaxation strength <=, which is proportional to the mean square end-to-end distance (r2), increased with M in dilute solution but decreased with C above the overlap concentration.

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

“…14, 16 The deviation of the present data of dilute solution from the Zimm theory can be attributed to a broader distribution of MW than used previously (M w =M n < 1:1). We also note in Figures 1 and 2 that the loss curves broaden with increasing C. Similar behavior was observed previously for semidilute solutions of polyisoprene, poly("-caprolactone), poly-(varelolacton), and poly(DL-lactic acid).…”

“…The results of Á"=C for PPO and PBO solutions are shown in Figures 7a and 7b, respectively. As observed for solutions of polyisoprene, [12][13][14] poly("-caprolactone), 16 and poly-(lactic acid), 17 the relaxation strength decreases with increasing concentration due to the screening of the excluded volume effect on the chain dimension. The horizontal lines indicate the levels of Á"= of the bulk PPO and PBO where is the bulk density.…”

“…Previously we found for semidilute polyisoprene solutions that A 0 ¼ 0:29, irrespective of the MW and solvent quality. [12][13][14] We also reported that A 0 for semidilute solutions of poly("-caprolactone) (PCL), poly(varelo lactone), and poly(DL-lactic acid) (PLA) in benzene were 0. 26 By extrapolating the log n vs. C½ plots to zero concentration as shown in Figure 3, we determined the relaxation time n0 at infinite dilution for PPO and PBO solutions.…”

“…Although many dielectric studies of the normal mode relaxation have been reported for bulk polymers, relatively small numbers of the studies on the normal mode relaxation in solution have been reported for polyisoprene, [12][13][14] poly("-caprolactone)(PCL), 15,16 poly(varelolactone), 16 and others. [17][18][19] In those studies, the effects of MW, concentration C, and solvent quality on the average relaxation time n , the relaxation spectrum, and relaxation strength Á" were investigated.…”

Dielectric Relaxation of Type-A Polymers in Melts and Solutions

“…A similar result was found also for the other type-A polymer, poly(e-caprolactone). [15] From these results, Adachi et al [15] concluded that the model describes the dielectric mode broadening (on the increase of c up to 3c*) and thus the broadening results from changes in the s p /s 1 ratio with c PI . However, the s 2 /s 2,0 and s 3 /s 3,0 ratios increase with c PI more rapidly than the model prediction ( Figure 14 a).…”