SYNTHESIS AND TRANSITION-TEMPERATURES OF SOME BRANCHED ALKYLOXYCARBONYLPHENYL ESTERS OF 3-(4'-N-ALKYL-BIPHENYL-4-YL)PROPANOIC ACID AND 3-(4'-N-ALKOXY-BIPHENYL-4-YL)PROPANOIC ACID AND THEIR LATERALLY FLUORINATED ANALOGS

A number of three ring diesters based on 4'-n-alkoxy- and 4'-n-alkyl-b iphenyl-4-ylpropanoic acid have been prepared to investigate the effec t on the liquid crystalline behaviour of these compounds of(a) incorpo ration of branched (achiral) end groups, and (b) laterally positioned fluorine atoms. Many of these diesters exhibited wide temperature rang e S-C and S-I phases, especially for compounds containing the 2-methyl pentyl end group. Lateral fluorination in both the 2- and 3-positions of the phenolic moiety reduced the melting point and smectic thermal s tabilities of the diesters. The reduction in S-C thermal stability by incorporation of a laterally positioned fluorine atom in the 2-positio n was very small, giving rise to compounds with very wide S-C ranges ( 40-50 degrees C). Unexpectedly, compounds containing a laterally posit ioned fluorine atom in the 3-position gave a number of crystal phases. Whether the diesters incorporated a branched terminal group or a late rally positioned fluorine atom, no nematic phase was observed.