Synthesis And Characterization Of Reactive Liquid Crystal Compounds

Liquid crystal elastomer(LCE), a novel liquid crystal polymer which combine the properties of oriented order of liquid crystals with rubberlike entropy elasticity, have attracted considerable interest due to its outstanding properties. Currently mesogenic units of most LCEs are attached to the molecular backbone along the director n. But their response to external stimulation is not well, so preparation of novel liquid crystals used as LCE is very necessary.Two new intermediates 2-allyloxy-4-octyloxy benzoic acid and 4-propyl -4'-hydroxybiphenyl were firstly synthesized, their synthetic procedures and processes were investigated and optimized. On the basis of the above stated works, two novel reactive liquid crystal monomers: 4'-propylbiphenyl-4-yl 2-allyloxy-4-octyloxy benzoate, 4-(4-propylcyclohexyl)phenyl 2-allyloxy-4-octyloxybenzoate were synthesized by esterification catalized by 4-pyrrolidinopyridine. There is an allyl in side chain of each liquid crystal monomer, so they are reactive. These liquid cystal monomers can produce polymerization or be branched on macromolecular chains. The optimized synthetic procedures summarized as follows:(1) A steric group was firstly introduced on -COOH group of 2,4-dihydroxybenzoic acid, in succession, bromooctane reacted with p-hydroxy, and 3-bromopropene reacted with n-hydroxy, at last 2-allyloxy-4-octyloxybenzoic acid was prepared by hydrolyzation reaction. Through comparison and analysis of different esterification and catalysis, it was concluded that ethyl esterification was the most effective and the yield of ethyl 2,4-dihydroxybenzate was 90.4% and the content was 99.7%. The second step was a alkyloxy substitution reaction that the yield (90.4%) was more 15% using wet acetone as solvent than dry acetone, and the product content was 99.7%. The yield of ethyl 2-allyloxy-4-octyloxybenzoate was 81.1%, higher than preceding reactiong due to the decrease of reaction energy induced by the delocalized π-electron of allyl group and the content was 99.9%. 2-allyloxy-4-octyloxybenzoate was prepared catalyzed by alkali in the solvent of methanol and water, the content was 99.3%, and the yield was 92.3%.(2) There were three methods, based on the principles of Friedel-Crafts and Кишнр- Wolff reaction, which could prepare 4-propyl-4'- hydroxybiphenyl: the use of anhydrous zinc chloride and propanoic acid; p- or p'- of bisphenyl was respectively...