Complex formation in mixtures of 4,4'-disubstituted diphenyldiacetylenes with cyanobiphenyls
Title:
Complex formation in mixtures of 4,4'-disubstituted diphenyldiacetylenes with cyanobiphenyls
Author:
Neubert, M. E. Keast, S. S. Humeniuk, E. E. Walsh, M. E. Petschek, R. G.
Appeared in:
Liquid crystals
Paging:
Volume 26 (1999) nr. 11 pages 1695-1706
Year:
1999-11-01
Contents:
We investigated 1 : 1 mixtures of a variety of 4,4'-disubstituted diphenyldiacetylenes (PTTP series) and cyano-containing mesogens for possible complex formation. Complexes were formed when alkyl/alkoxy cyanobiphenyls (CB series) were mixed with alkyl/alkoxy PTTP homologues. We found complexes having a melting temperature higher than that for either component, and complexes with lower melting temperatures. A fluoro substituent on the PTTP gave an enhanced nematic phase and a cyclohexane ring in place of a benzene ring yielded an enhanced smectic A phase, but a cyano on the PTTP gave poor liquid crystalline properties. Phase diagrams were constructed for PTTP-2415-CB and PTTP-24180-CB mixtures. Both complexes formed had melting temperatures higher than those f o ~eit her component. These complexes were recrystallized and shown by X-ray studies to be 1: 1 complexes. The PTTP-2415-CB complex showed only a monotropic nematic phase, but the PTTP-24180-CB complex showed induced smectic A and hexatic B phases in addition to an enantiotropic nematic phase.