Ionization-liquid-crystalline polymer synergistically reinforced poly(ethylene terephthalate) due to interfacial compatibilization by ion-dipole interactions

To enhance the compatibility of poly(ethylene terephthalate) (PET)/liquid crystalline polymer (LCP) composite, thereby mechanically strengthening the PET matrix, an optimally compatibilized composite of chain-extended and -carboxylated PET ionomer and poly(4-hydroxybenzoic acid-ran-6-hydroxy-2-naphthoic acid) (HBA-HNA) was successfully prepared. Upon PET carboxylated chain extension with pyromellitic dianhydride and subsequent ionization with Zn(OH)(2), the compatibility of the composite was distinctly improved, as verified by the refined dispersed-phase morphology, increased number of refined HBA-HNA fibrils, reduced crystallinity, and improved complex viscosity. Compared with PET, the optimally compatibilized composite displayed a 70.1 and 148.7% increase in Young's modulus and tensile strength, respectively. Tentatively mechanistically, the interfacial interaction may change from weak hydrogen bonding to strong ion-dipole interactions due to the introduction of ionic groups, which remarkably boosts the interfacial compatibility, thereby achieving synergistic effects of the ionization and HBA-HNA inclusion to maximally strengthen PET. It seems that the synergistic ionization/LCP inclusion by a one-pot method establishes a promising preparation approach to commercial PET engineering resins.