Co[poly(ethylene terephthalate‐p‐oxybenzoate)] thermotropic copolyester. II. X‐ray diffraction analysis

Abstract A series of co[poly(ethylene terephthalate‐ p ‐oxybenzoate)] thermotropic copolyester with different compositions were prepared by the copolymerization of either poly(ethylene terephthalate) (PET) polymer or its oligomer with p ‐acetoxy‐benzoic acid. The polymeric products were subjected to solid‐state polymerization for various time intervals. Effects of composition ratio and solid‐state polymerization time on X‐ray diffraction behavior were investigated. It is found that the effect of transesterification induced by solid‐state polymerization causes an increase in crystallinity with the copolyesters having high mol % of p ‐oxybenzoic acid (POB) moiety and causes a decrease in crystallinity with the copolyesters having high mol % of PET moiety. In general, the crystallinity of copolyesters is first increased and then decreased as solid‐state polymerization time proceeds. However, the crystallinity of copolyester having POB/PET = 80/20 composition is increased generally at 4‐h solid‐state polymerization. It is also found that the crystallinity of copolyesters is decreased by quenching. The copolyester based upon either PET oligomer with 4‐h solid‐state polymerization or PET polymer with 8‐h solid‐state polymerization shows the most similar X‐ray diffraction pattern with that of Eastman 10109. © 1993 John Wiley & Sons, Inc.