Mikhailenko V. Chiral diesters of p-terphenyl dicarboxylic acid and fluorinated alcohols as effective components of ferroelectric liquid crystals with a short helical pitch

Ferroelectric liquid crystal (FLC) materials are promising alternative to nematic LCs, due to their fast switching in the range of hundreds to microseconds under moderate driving voltages. For the realization of modern electro-optical effects from FLC materials, it is required to induce a nanoscale pitch of the helicoid and high spontaneous polishing. We have stated suitability criteria of chiral organic compounds for practical use in the short-pitch FLC materials: first one is high helical twisting power (HTP) which is characteristic of CCs and is inversely proportional to a value of the pitch of a supramolecular helix. HTP is to be not less than 35 μm–1. Second, effective induction of spontaneous polarization (PS) in a FLC at the level at least 150 nC/cm2 should take place. Relying on some regularities found in literature, we have stated primary structural criteria which may affect effectivity of chiral components intended for use in the short-pitch FLC materials: (1) presence of two flexible polar groups separated by p-terphenyl core in a CC molecule; (2) presence of polar trifluoromethyl groups at chiral centers; (3) presence of two flexible terminal alkyl substitutes which may take an effect by strengthening interaction between molecules in adjacent smectic layers; (4) substitution of an alkyl at the chiral center with more polarizable aryl moiety; (5) introduction of a bifunctional lactate moiety to CC molecules. The thesis is aimed at synthesis and study of new efficient fluorine-containing chiral components of ferroelectric LC materials with short helical pitch. Preparative synthetic methods for new chiral diesters of p-terphenyldicarboxylic acid and fluorine-containing alcohols are developed. Systematic series of chiral symmetric of p-terphenyldicarboxylic acid diesters containing 1,1,1-trifluoroalkane-2-olic and 2,2,2-trifluoro-1-p-tolylethanolic residues as well as combination of chiral lactate and 1,1,1-trifluoroalkane-2-ol fragments are obtained. New chiral derivatizing reagent l-methyl-phthalate is proposed for determining enantiomeric purity of chiral secondary fluorine-containing alcohols being key intermediates for the synthesis of the target diesters. Using l-menthylphthalate, synthetic methods for enatiomerically pure (R)- and (S)-enantiomeric 1,1,1-trifluoroalkane-2-ols are developed. Properties of the target compounds as chiral components of ferroelectric LC materials are investigated. The effect of molecular structure of chiral diesters of p-terphenyldicarboxylic acid on the properties of short-helix FLCs is obtained. Based on the new chiral components, FLC materials for use in modern photonic devices were developed. An effective method for the resolution of racemic trifluorolactic acid is proposed.