G. Bergman

Influence of Disclination Density and Crystallinity on the Transport Properties of a Liquid Crystalline Copolyester

The effect of annealing on the structure and transport properties of a compression‐molded liquid crystalline co‐polyester (Vectra® A950) consisting of 73mol% poly(hydroxybenzoic acid) and 27mol% poly(hydroxy‐naphthoic acid) was studied. Films were annealed above (310°C) or below (260°C) the melting point. The structure was studied with density measurements, optical microscopy, differential scanning calorimetry and wide‐angle X‐ray diffraction. It was observed that the density increased as a linear function of the logarithm of annealing time and that the crystallinity increased only on annealing below the crystal melting point. The increase in density above the melting point, and also to a large extent below the melting point, must have occurred through improved molecular packing but without any reduction in disclination density, as revealed by optical microscopy. The methanol diffusivity, obtained from desorption data, showed a moderate decrease with increasing density; the trend was only significant within a 60% confidence limit.