Sequentially ordered,thermotropic aromatic copolyesters: Synthesis and comparison of their properties with random copolyesters

Synthetic methods of aromatic copolyesters having ordered comonomer sequence are described. In order to obtain a regular sequence copolyester, one first has to prepare a dimeric or trimeric compound with a predesigned sequence via a multistep route and then polycondense it with another difunctional compound. Low reaction temperature is required to avoid the occurrence of undesired interchange reactions that would lead to randomization of the comonomer sequence. Sequentially ordered copolyesters exhibit significant differences in thermal transitions, crystalline properties, and occasionally even in liquid crystallinity when compared with the properties of the corresponding random copolyesters. According to the preliminary results randomization in comonomer sequence of sequentially regular aromatic copolyesters above their melting points is rather rapid.