关键词: 4'-酰基-4-羟基联苯酯, 液晶, 近晶相

Abstract: Biphenyl esters are useful and important materials for liquid crystal dispiays. Re cently it is well known that the presence of an acyl terminal group which atteched with its carbonyl carbon atom directly to an aromatic core,in liquid crystalline compounds would usually increase both the molecular rigidity and polarity, and as a result, the compounds could show some better mesomorphic properties than those that contain the same molecular backbone but carry only R-or RO-terminal chains.Thus, we synthesized eight new 4'-acyl-4-biphenylol esters 5_a-hwith 4-biphenylol as starting material to study the effect of molecular structure on phase behavior of these esters. Chemical structures of these com pounds were determined by IR, ¹HNMR, MS and elementary anaiysis. Their liquid crystal properties were tested by hot stage polarizing microscopy and differential scanning calorime try. Except compound 5_h, these compounds have a wide tempetature range of mesophase and high thermostability. Some of them show a monotropic phase transition in the S_cphase. The S_A-S_cphase transition of compound 5_cis a second type phase transition. Compound 5_g,though there is no chiral carbon in the molecule, displays a stripped focal conic texture in the S_cphase.The effect of molecular structure on liquid crystal properties was discussed.

Key words: 4'-Acyl-4-biphenylol esters, Liquid crystallines, Smectic phase