Novel liquid crystalline copolyester containing amphi-mesogenic units toward multiple stimuli-response behaviors

Abstract

Novel liquid crystalline copolyesters named as P(BH-co-BPn)PS, with azobenzene and biphenyl group mesogenic units, were designed and synthesized conveniently by one pot melt polycondensation. All P(BH-co-BPn)PS copolyesters showed good thermal stability, smectic liquid crystalline behavior with π–π interactions in the polymer chains. As the three different functional building blocks (azobenzene and biphenyl chromophores, liquid crystals, π–π interactions) work together, P(BH-co-BPn)PS were responsive to external stimuli at the molecular level, exhibiting thermal shape memory, photo-induced bending and self-healing behaviors at the macroscopic level. It was noteworthy that the different responsive properties of the photo-active azobenzene and photo-inert biphenyl mesogenic units made a great contribution in the photo responsive behavior of these copolyesters, resulting in reversible bending and unbending behaviors for P(BH-co-BP30)PS. In addition, without the chemical crosslink, these copolyesters could be reshaped and reprocessed. Taking advantage of the features, these copolyesters containing amphi-mesogenic units can help to facilitate numerous applications like soft actuators and smart materials.