The Effect of Methyl Group Position in Branched Alkyl Chains on the Phenolic End of 4,4′-Disubstituted Phenylbenzoates on Mesomorphic Properties and Some Optically Active Analogs as Ferroelectric Liquid Crystals

Abstract

A select number of homologs of the branched chain (BC) Cs ester series: n in which m = 0-3 and n = 0-2, and X = R, RO, and &C02 have been synthesized to study the effect of branching and the position of the branching methyl group on mesomorphic properties. This effect was also determined for the BC cyclohexane diesters: Me to test the generality of any trends observed in a different structural series. Mesomorphic properties of the esters were determined by hot-stage polarizing microscopy. Nematic, S,, S,, and S(,?, phases in various combinations were observed. Both clearing and melting temperatures for the BC phenylbenzoates, when X = RO and C&O, were always lower than for the analogous straight chain (SC) esters containing the same number of carbon atoms, as were in the backbone of the BC.Comparisons of the effect of the BC on the mesomorphic properties of these esters are made with the effect observed in a variety of other thioesters, substituted phenylbenzoates, and the analogous biphenyl compounds. Often Sc phases are enhanced at the expense of the SA phase, and N phases seem most preferred when the methyl group is in the 2-position on the chain of the phenol/thiol. Clearing temperatures are always lower than in the analogous SC compounds and melting temperatures are usually lower. However, enough discrepancies occur to make the melting trend a less general one. The effect of location of the methyl group on transition temperatures in C5 BC phenylbenzoates is similar to that observed previously for the C4 BC esters, i.e. they tend to increase as the methyl group is moved further from the benzene ring. This trend, however, does not always occur in other systems such as the thioesters.Mesophase ranges were good among the BC phenylbenzoates with X = RO and room temperature SA-Sc combinations were found in this series when rn = n = 2. Therefore, several homologs were prepared with an optical isomer of this chain to determine their usefulness in mixtures as ferroelectric materials.

<title>Influence of length of alkyl terminal chain on mesomorphic properties of new chiral liquid crystalline homologous series of thiobenzoates</title>

“…4,4'-biphenyl disubstituted (2) was obtained in the reaction of on the original substance 4-hydroxybiphenylcarboxylic methyl ester (1) with (R)-(-)-2-octanol (Mitsunobu reaction) in the presence of dry ether. The compound (2) was isolated from the reaction mixture using chromatographic column.…”