Synthesis and polymerization kinetics of bio-based liquid crystal polyesters based on plant-derived phenolic acid

Liquid crystal polyesters (LCPs) have been employed in various applications, however, their sustainability of the replacement of petroleum-based materials by biomass resources remains a challenge. In particular, using low-cost, readily available bio-based monomers to synthesize LCPs is rarely explored. Herein, vanillic acid and ferulic acid as easily accessible plant-derived phenolic acids are used to prepare bio-based LCPs. Liquid crystal behaviors of the as-prepared LCPs can be observed through a polarized optical microscope, and their polymerization kinetics are studied by thin-film polymerization technique to reveal the relationship between the copolymerization composition and liquid crystal (LC) behaviors. The formation of LC for the as-prepared LCPs can be promoted by the increase of vanillic acid composition but inhibited by the increased ferulic acid composition. The prepared bio-based LCPs show high thermal stability with high glass transition temperatures of over 80 °C and high decomposition temperature of about 300 °C. This work develops two available bio-based monomers for preparing LCPs, showing a good promise in sustainability.