LIQUID-CRYSTALLIZATION INDUCED REACTIONS - MICROSTRUCTURE AND MORPHOLOGY OF COPOLYESTERS SYNTHESIZED BY TRANSESTERIFICATION OF PET WITH SOME LCP MONOMERS

The transesterification of poly(ethylene terephthalate) (PET) with a m ixture of sebacic acid (S), 4,4'-diacetoxybiphenyl (B) and 4-acetoxybe nzoic acid (H), carried out under conditions expectedly favoring the f ormation of a p(ET-SBH) random copolyester, produces biphasic material s with an isotropic matrix and a highly fibrous, liquid-crystalline di spersed phase. Spectroscopic, calorimetric, microscopic and diffractom etric characterization of the fractions separated by solvent extractio n has shown that the two phases consist of practically random copolyes ters having different average composition. Interestingly, the degree o f aromaticity of the matrix is even lower than that of PET, whereas th at of the minor phase is appreciably higher than that calculated for t he SBH copolyester that would be produced from the monomer mixture in the absence of FET. This unexpected result is interpreted on the basis of an enthalpy-driven progressive diffusion of aromatic-rich material toward the mesophase which segregates at an early stage of the polyco ndensation within the isotropic mixture of low molar mass oligomers in itially produced by the PET acidolysis. Thus, an increasing differenti ation, rather than an equilibration, of the composition of the two pha ses takes place. It is noteworthy that, despite the strong composition al difference, the two phases of these products show fairly good compa tibility and interfacial adhesion.