SYNTHESIS AND CHARACTERIZATION OF NOVEL AROMATIC POLYESTERS DERIVED FROM THIOPHENES

Novel aromatic polyesters have been synthesized by solution condensati on reactions between hydroquinone and 3,4-disubstituted 2,5-thiophened icarbonyl chlorides. The introduction of phenyl substituents in these poly(p-phenylene 3,4-disubstituted 2,5-thiophendicarboxylate)s did not enhance the fusibility nor the solubility of the resulting material w hen compared to the unsubstituted parent polyester. The presence of et hyl groups led to the formation of an insoluble semicrystalline aromat ic polyester with a melting transition at 304 degrees C. Poly(p-phenyl ene 3-methyl-4-propyl-2,5-thiophenedicarboxylate) was found to be solu ble in chloroform and exhibited a melting transition at 242 degrees C. All these polyesters are stable up to 350-400 degrees C. However, in contrast to the unsubstituted parent polymer, all these aromatic polye sters did not show any evidence of liquid crystallinity in the melt. O n the basis of theoretical calculations, this behaviour can be related to the ca. 143 degrees core angle of 3,4-disubstituted thiophenes.