Andrew Teh Hu

Thermotropic copolyesters modified with nonmesogenic rigid groups

SummaryTwo series of copolyesters of sebacic acid, 4,4′-biphenol and a nonmesogenic rigid diol which was either bisphenol A (BPA series) or hydroquinone (HQ series) were prepared by melt polycondensation. The thermal transitions and melt birefringence which were investigated by DSC and polarized microscope respectively. Homopolyester of 4,4-biphenol and sebacic acid (PB8) was found to show two transition temperatures corresponded to Tm and Ti respectively. For the BPA series, the incorporation of amorphous bisphenol A unit by copolymerization decreased both Tm and Ti and completely destroyed the mesophase as the content of bisphenol A unit was over 50 mole%. For the HQ series, the incorporation of crystalline hydroquinone unit decreased Tm to more extent, but decreased Ti to less extent as compared to the BPA series. When the hydroquinone unit was as high as 80 mole%, the mesophase was completely destroyed.