Conformational Peculiarities Of Alcohols Incorporated In Lyotropic And Thermotropic Liquid Crystals

Conformational characteristics of 1-butanol incorporated not only in hexagonal and lamellar aggregates formed by a lyotropic liquid crystal composed of sodium octanoate, 1-butanol, and water but also in a thermotropic liquid crystal, 4'-methoxybenzylidene-4-n-butylaniline (MBBA), have been investigated from H-2 NMR quadrupolar splittings of the perdeuterated and partially deuterated compounds. In the lyotropic phases, 1-butanol shows strong trans preferences and renders itself extended, and octanoate decreases the trans fraction toward the methyl terminal to fill the inner space of the aggregate on behalf of 1-butanol. In MBBA, 1-butanol prefers globular conformations. This tendency was also indicated from the phase behaviors of 1-butanol/MBBA and 1-decanol/MBBA systems. In the nematic field, two successive C-C bonds of 1-butanol mostly adopt g(+/-)g(+/-) conformations, which are formed in the vicinity of the headgroup of 1-decanol in the lamella of the sodium octanoate/1-decanol/water system. A large degree of conformational freedom near the hydroxyl group of alcohols, being shown by ab initio molecular orbital calculations at the Gaussian-2 level, permits them to change conformation for each environment.