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

Abstract

A series of compounds with biphenyl as a mesogenic fragment having a structure that models LC dimers and polymers with mesogenic groups of the side chain and a star-shaped structure have been synthesized. An approach to the synthesis of such compounds under soft conditions without a complex procedure of purification with quantitative yield has been developed; it is an implementation of the click chemistry methods for synthesizing LC compounds. It is shown for compounds with biphenyl as a mesogenic fragment that the LC state is observed only when the number of biphenyls in one compound is 3 (i.e., the compounds are similar to polyesters with biphenyl as a mesogenic fragment, which exhibit LC behavior). For compounds with the potentially weak mesogen such as biphenyl, the decisive factor in the formation of the LC state and smectic mesomorphism is the formation of intermolecular hydrogen bonds.