A thermally stimulated current/relaxation map analysis of the relaxation processes in aromatic polyester, liquid crystal polymer film

Abstract

AbstractThermally stimulated current (TSC) and relaxation map analysis (RMA) have been applied to the examination of dynamics of thermally induced relaxation processes in highly oriented, wholly aromatic, polyester liquid crystalline polymer films. Films of two compositions were examined. A primary distinction in composition was the difference in level of 6‐hydroxy‐2‐napthoic acid. Following an analysis protocol developed by Sauer et al., it was found that values of activation enthalpy were well above the zero entropy value at temperatures well below the Sauer “Tg.” This indicates a high level of cooperativity in rotational relaxation processes even at low temperatures. Cooperative rotational relaxation domains were postulated to account for this behavior. The persistence of cooperativity above the Sauer “Tg.” is evidence that these materials did not undergo a conventional glass transition at any temperature in the range–80 to 200°C. The behavior of these materials as a model system of “loosely bundled rods” was examined using a modified Barker–Crine analysis. This type of model behavior seemed to fall off at relatively low temperatures. The occurrence of rotational processes at high temperatures with little or no loss in orientation suggests that polymer chains are physically constrained to maintain their relative positions. © 1994 John Wiley & Sons, Inc.