Synthesis And Properties Of Diolefin Liquid Crystal Compound

Above all the literatures, we designed to a new synthesize method of diolefin liquid crystal compound, and synthesis four compounds of diolefin fluorous liquid crystal compound which were not reported (E)-1,2-difluoro-4-(4-(2-(4-(4-vinylcyclohexyl)cyclohexyl)vinyl)Cy- clohexyl)benzene,(E)-1-methyl-4-(4-(2-(4-(4-vinylcyclohexyl)cyclohexyl)vinyl)cyclohexyl)benzene,(E)-1-methoxy-4-(4-(2-(4-(4-vinylcyclohexyl)cyclohexyl)vinyl)cyclohexyl)benzene,(E)-1-methoxy-4-(4-(2-(4-(4-vinylcyclohexyl)cyclohexyl)propenyl)cyclohexyl)benzene. Structures of the liquid crystal compounds were confirmed by 1HNMR, MS. The properties of liquid crystal compounds were observed by Differential Scanning Calorimeter(DSC) and Polarizing Optical Microscope (POM).This thesis containsists of five parts:Part one, the elementary knowledge about liquid crystal materials was briefly introduced,and the important progress made in the fild of diolefin liquid crystal compound was reviewed.Part two, the three triphenylphosphonium of trans-substitued-phenylcyclohexyl iodomethane were synthesized from substitued-bromobenzene and 1,4-cyclohexanedione monoethylene acetal via ten step reactions, namely Grignard reaction, dehydration reaction, catalytic hydrogenation, hydrolysis, Wittig reaction, hydrolysis, isomerization, aldehyde reduction, substitution of hydroxyl by iodine, addition. The important intermediate compounds was identified by 1HNMR.Part three, the two E-4-(4- substituted-vinylcyclohexyl)cyclohexanecarbaldehyde were synthesized from bicyclohexane-4,4'-dione mono-neopentyleneacetals via seven step reactions, namely Wittig reaction, hydrolysis, Wittig reaction, hydrolysis, isomerization, Wittig reaction, hydrolysis. The important intermediate compounds was identified by 1HNMR.Part four, the triphenylphosphonium of trans-substitued-phenylcyclohexyl iodometh- ane and E-4-(4- substituedvinylcyclohexyl)cyclohexanecarbaldehyde can be used to synthesize many liquid crystal monomers via Wittig reaction, hydrolysis. Four liquid crystal monomers have been synthesized:(E)-1,2-difluoro-4-(4-(2-(4-(4-vinylcyclohexyl)cyclohexyl)vinyl)Cy-clohexyl)benzene, (E)-1-methyl-4-(4-(2-(4-(4-vinylcyclohexyl)cyclohexyl)vinyl)cyclohexyl)benzene, (E)-1-methoxy-4-(4-(2-(4-(4-vinylcyclohexyl)cyclohexyl)vinyl)cyclohexyl)benzene, (E)-1-methoxy-4-(4-(2-(4-(4-vinylcyclohexyl)cyclohexyl)propenyl)cyclohexyl)benzene. The purity of all of the products were analyzed by gas chromatography. The target compounds were identified by 1HNMR and MS.Part five, we surveyed their phase-transition temperature and chemical stability by DSC-TG, and obtained their POM patterns. The results showed that these liquid crystal compound exihibit high clearing points(>300℃), good chemical stability and broad temperature range of mesomorphic phase(>180℃). They were thermotropic tantomeric liquid crystals.