RELAXATION AND CONFORMATIONAL STUDIES ON POLYMERS WITH LARGE CONDUCTIVE CONTRIBUTIONS TO THE DIELECTRIC LOSS

This work focuses on the study of the dielectric behavior of asymmetri c molecular chains with high electronic unsaturation on the side group s, taking as a model poly(4-benzoylphenyl acrylate) (PBA). This polyme r presents a prominent glass-rubber relaxation, named alpha, followed by two secondary processes that under decreasing temperatures are call ed beta and gamma absorptions. Similar relaxations are found in the me chanical spectrum. At low frequencies, free charges and interfacial co ntributions to the dielectric a relaxation are dominant and a method i s proposed to determine each of them. The experimental intramolecular correlation coefficient g(intra) = 1 + SIGMA(i not-equal j) [cos gamma (ij)] for PBA chains, where gamma(ij) is the angle between the dipoles associated with i and j repeating units, is 0.81 at 30-degrees-C and its temperature coefficient d In g(intra)/d T has a value of 1.3 x 10( -3) K-1 in the interval 30-60-degrees-C. A 4 x 4 rotational states sch eme gives a good account of these experimental results. The correlatio n coefficient g, which includes both the intermolecular and intramolec ular interactions, is in very good agreement with the value of g(intra ), suggesting that intermolecular interactions are negligible in this polymer.