MISCIBILITY AND TRANSESTERIFICATION IN BLENDS OF LIQUID-CRYSTALLINE COPOLYESTERS AND POLYARYLATE

Blends of poly(oxybenzoate-p-ethylene terephthalate) (POB-PET) and pol yarylate were confirmed to be a partially miscible system by different ial scanning calorimetry. When 60/40 POB-PET/PAr blend was annealed at high temperature (above 270 degrees C) for several minutes, the ester -ester interchange( transesterification)in the blend took place immedi ately, as evidenced by Fourier Transformed infrared analyses. The anal ysis of the blend annealed at 290 degrees C by H-1-C-13 nuclear magnet ic resonance disclosed that there were four new diads appearing in 15 min and an additional one produced in 60 min during the heat treatment . The miscibility between POB-PET and polyarylate increased with the m ol concentration of these new diads judging from differential scanning calorimetry. The evolution of the concentration of the diad ethylene glycol-isophthalate during the annealing can be described by a second- order reaction. The activation energy of forming the diad ethylene gly col-isophthalate was 26.5 kcal/mol, and the preexponential factor for the transesterification reaction is 3.7 x 10(8) min(-1). (C) 1998 John Wiley & Sons, Inc.