THE KINETICS OF TRANSESTERIFICATION IN BLENDS OF LIQUID-CRYSTALLINE COPOLYESTER AND POLYCARBONATE

The kinetics of transesterification in blends of thermotropic copoly(o xybenzoate-ethylene terephthalate) and polycarbonate at melt state wer e analysed quantitatively with C-13 nuclear magnetic resonance, and we re then modelled by a phenomenological equation. It was found that the activation energy for the transesterification reaction between the po ly(oxybenzoate) segment in copoly(oxybenzoate-ethylene terephthalate) and polycarbonate was more than twice that for the transesterification reaction between the poly(ethylene terephthalate) segment and polycar bonate (i.e. 94.6 versus 41.8 kcal/mol). This is probably due to the s tronger chemical bond in oxybenzoate-oxybenzoate that in ethylene-tere phthalate. Additionally, owing to the rigid-rod nature of the poly(oxy benzoate) segment, the frequency factor in the transesterification rea ction in poly(oxybenzoate) segment and polycarbonate is much higher th an that in poly(ethylene terephthalate) segment and polycarbonate (i.e . 10(36) versus 10(14) min(-1)). (C) 1998 Elsevier Science Ltd. All ri ghts reserved.