Structure–Property Relationship of Highly π-Conjugated Schiff-Base Moiety in Liquid Crystal Diepoxide Polymerization and Mesophases Stabilization

A study of the structure–property relationship of the highly π-conjugated Schiff-base moiety in polymerization of a liquid crystal (LC) diepoxide oligomer (PBMBA) and mesophases stabilization has been investigated. We first proposed two exothermic peaks distinctly observed in nonisothermal polymerization curves for thermal copolymerization of PBMBA monomer with a diamine comonomer that corresponded to two different reactions, namely, an epoxy-amine polymerization and anionic polymerization. For PBMBA, note that an unexpected homopolymerization accompanying an appearance of enantiotropic mesophase transitions had taken place in the absence of any initiators, evidencing the possibility of an anionic mechanism yielding a homopolymer. A novel Schiff-base model compound (SBM) was synthesized and used to induce the polymerization of different types of epoxies. Based on the structure–property relationship, we considered a specific role of highly π-conjugated Schiff-base moieties in the anionic polymerization of PBMBA and hoped the mesophases could be stabilized using this mechanism, which may provide a key strategy for design of the polymer-dispersed liquid crystal (PDLC) materials via a chemical process.