Oxybenzoate-ethylene terephthalate copolyesters

Copolyesters of poly(ethylene terephthalate) and 4-acetoxybenzoic acid (PET / oxybenzoate) were synthesized by Jackson et al. through high temperature melt transesterification. However intricate details pertaining to the polyesterification kinetics have remained unexamined. In this system, insertion of 4-oxybenzoate moieties, with stiff rod like conformations, into flexible PET chains fosters the development of thermotropic character within a definite range of copolyester composition. 

EI-MS was used to analyze an aromatic copolyester with units of p-oxybenzoate (PO) and of ethylene terephthalate (ET). The El mass spectra were recorded up to 480°C. At these temperatures, the chain cleavage is totally selective, since PO units are stable and ET units are not. Chain statistics was applied to the El mass spectra and a good agreement was foimd between the computed and the known composition. ... 

Shinn Ted-Hong, Lin Chen-Chong, Lin David, C. (1995). Studies on Co [Poly( Ethylene Terephthalate-p-oxybenzoate)] Thermotropic Copolyester Sequence Distribution Evaluated from TSC Measurements. Polym, 36(2), 283-289. 

All of the reactions listed above can be equally applied to the preparation of aromatic copolyesters from almost any combination of hydroxyacids, dicarboxylic acids and biphenols of the types listed in Table 3. In general, the copolymers so obtained are random or statistical in composition. Furthermore, the acidolysis reaction has been successfully applied to preparation of random copolyesters by interchanging monomers and high molecular weight polymers, most notably in the preparation of poly(ethylene terephthalate-co-oxybenzoate) by the insertion reaction of /7-acetoxybenzoic acid with preformed poly(ethylene terephthalate), as follows... 

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