Poly(vinyl benzoate)-backbone mesogen-jacketed liquid crystalline polymers

Abstract

Previously reported polymer backbone structures of mesogen-jacketed liquid crystalline polymers (MJLCPs) are still limited to polyacrylate, polystyrene, polyacetylene, polysiloxane, polythiophene and polynorbornene. In this manuscript, we describe a new system of MJLCPs with poly(vinyl benzoate)-backbone (PVBnB), which were synthesized by solution polymerization and bulk photo-polymerization methods. Due to the low reactivity of the vinylbenzoate group, we cannot achieve a high degree of polymerization. Ironically, benefiting from this low reactivity, we successfully prepared several loosely cross-linked MJLCP (xPVBnB) films with homogeneous- or homeotropic-alignment, for the first time by using UV-illumination on a unidirectional oriented mixture of vinylbenzoate monomers, crosslinkers and photo-initiators to perform polymerization and cross-linking at the same time, which are however extremely difficult for the much more reactive acrylate-type or styrene-type MJLCPs’ precursor monomers due to the spontaneous thermal-polymerization reactions occurring at high temperatures. Experimental results show that PVBnB can form nematic or smectic phases depending on the alkyl chain length, xPVBnB films present very small elastomeric transformations (i.e. shrinkage/wrinkle) during the LC-to-isotropic phase transition.