Thermal properties of blends of a thermotropic liquid crystalline copolyester of poly(hydroxy benzoic acid-co-ethylene terephthalate) and polyarylate

Summary Thermal properties and transesterification reaction of blends of polyarylate (PAr) and a thermotropic liquid crystalline polymer (LCP) were investigated by differential scanning calorimetry (DSC) and Fourier Transform infrared (FT-IR) spectroscopy. In the thermogram of PAr-LCP blends, two glass transition temperatures (T_gs) were observed. Phase behavior of the blends revealed that the LCP dissolved more in the PAr-rich phase than did the PAr in the LCP-rich phase, indicating partial miscibility between two polymers. The polymer-polymer interaction parameter (χ₁₂) was calculated, and ranged from 0.069 to 0.076. In the calculation of the χ₁₂, the anisotropy of the LCP was considered. After annealing, the two T_gs of the blends were shifted toward the center. In the FT-IR spectroscopy study of the annealed PAr-LCP blends, three new characteristic peaks of the ester group were detected. The DSC and FT-IR results suggested that transesterification reaction between PAr and LCP occurred under the annealed condition. Received: 12 May 2000/Revised version: 11 July 2000/Accepted: 24 July 2000