Nematic,smectic and columnar phases of main-chain liquid crystal polyethers

A number of interesting thermotropic mesophases and transitions occur in main-chain polyethers and copolyethers based on aliphatic spacers and various semi-flexible mesogens of the general 1-(4'-hydroxyphenyl)-2-(2-R-4-hydroxyphenyl)ethane (RBPE) or 1-(4'-hydroxybiphenyl-4-yl)-2-(4-hydroxyphenyl)propane (TPP) type. The unusual effects described here are (i) nematic-nematic transition, (ii) smectic-B (crystal-B) phase and its shear-induced orientation, (iii) calamitic columnar phase, and (iv) nematic-columnar phase sequence.