The Synthesis and Liquid Crystal Transition Temperatures of a Broad Range of Mesogens Incorporating Four-Unit-Linking Groups I

Abstract

The vast majority of liquid crystals synthesized over the last one hundred years contain aromatic and/or aliphatic rings joined together either directly or by a central linking unit.¹ These central linkages have nearly always consisted of two units (e.g., ‒COO‒, ‒-CH₂CH₂‒, ‒CH₂O‒, ‒CH˭CH‒, ‒C≡C‒, ‒CH˭N‒, ‒N˭N‒, ‒N˭N(O)‒) of which only a few have found wide commercial acceptance for display device applications.² Various investigations^1–5 of compounds incorporating central linkages with four constituent elements (e.g., ‒CH₂CH₂COO‒, ‒CH˭CHCOO‒, ‒C₄H₈‒) reveal a pronounced tendency for smectic mesophase formation. As yet no compounds suitable for display devices have been prepared. We now report a systematic study of new mesogens incorporating four-unit-linkages which are eminently suitable for electrooptic display device applications (e.g., TN, STN, TFT, ECB, GH, SSFLCD, etc.) exhibiting wide-range enantiotropic smectic and nematic mesophases of positive as well as negative dielectric anisotropy.

Key Words:

• liquid crystals
• four-unit linking group
• synthesis
• electrooptic display