Synthesis and Mesomorphic Properties of Biphenyl Derivatives with Central Unit Based on 1,6-Hexamethylene Diisocyanate Oligomers

A number of compounds with biphenyl as a mesogenic fragment and a structure simulating LC dimers, polymers with mesogenic side chain groups and a star-shaped structure have been synthesized. An approach for the synthesis of such compounds under mild conditions and without a complex purification procedure with a quantitative yield, has been developed. The approach is the implementation of “click chemistry” methods for the synthesis of LC compounds. It has been shown that the LC state is observed only if there are three biphenyls in one molecule, i.e., the compounds appear to be similar to polyesters with biphenyl as a mesogenic moiety. The determining factor in the formation of the LC state and particularly smectic mesomorphism of compounds with such a potentially “weak” mesogen as biphenyl is the formation of intermolecular hydrogen bonds.