New thermotropic chiral nematic copolymers using (1S,2S,3S,5R)-(+)- and (1R,2R,3R,5S)-(-)-isopinocampheol as building blocks

Abstract

Thermotropic chiral nematic side-chain copolymers were synthesized and characterized by using (1S,2S,3S,5R)-(+)- and (1R,2R,3R,5S)-([minus])-isopinocampheol as the chiral building blocks. The helical twisting power was found to correlate with the volume swept out by the chiral pendant group via rotation for a given nematogenic monomer. However, the enhanced mesomorphic order introduced in both the nematogenic and chiral monomers as a result of an increased extent of conjugation or a shortened spacer length was found to reduce the helical twisting power of the resultant copolymer. Hence, both factors have to be taken into account as the helical twisting power of a copolymer system is to be optimized for a specific application. The present work also generalized the previous observation that the inversion of chirality of the pendant group results in helical sense reversal, although the role of the absolute configuration of the chiral moiety is not yet clearly understood.