DIELECTRIC-RELAXATION STUDIES OF AROMATIC POLYAMIDES

Dielectric relaxation spectroscopy (DRS) is presented for a family of four aromatic polyamides trying to relate the structure of the lateral groups to the molecular mobility. A prominent sub-T-g, absorption is always seen followed in some cases by remanent dielectric activity at room temperature and a subsequent increase of the loss permittivity. T he low temperature relaxation is analyzed in terms of a Fuoss-Kirkwood equation to obtain the broadness and the strength of these relaxation s as well as the activation energy (ranging from 10 to 11 Kcal/mol). T he low frequency conductive peak shows in each case a half-width highe r (1.30) than those corresponding to a single relaxation time peak (1. 144). These values of the half-width are an indication of the complex character of these phenomena. A final discussion of the rotational bar riers of the lateral chains rules out that such motions are the only m olecular origin for the gamma relaxation. Instead, some kind of motion involving the main chain and where the interchain interactions play a significant role should be considered as responsible for that relaxat ion. (C) 1997 John Wiley & Sons, Inc.