New series of 4-(4 '-octyloxybiphenyl-4-yloxymethyl)benzoic acid derivatives with mesogenic properties

Three homologous series of (4'-octyloxybiphenyl-4-yloxymethyl)benzoic acid derivatives were synthesised and studied. The compounds, substituted by n-a lkyl esters, reveal strong discrimination of the tilted phases formation up on elongation of the alkyl group. In compounds with 2 methylalkyl chains, t ilted phases were exclusively observed with both ferroelectric and antiferr oelectric properties. It has been observed that for chiral derivatives an e longation of the chiral chain leads to odd-even effect on the polar propert ies. Also elongation of non-chiral alkoxy terminal chains affects the polar properties. For short homologues the antiferroelectric phases dominate, wh ile for long homologues only ferroelectric behaviour is observed. The influ ence of strongly polar lateral groups (Cl, Br, NO2) attached to the bipheny l ring on LC phase properties was also determined. It was detected that mon osubstituted compounds have lower mesogenic stability then their disubtitut ed counterparts. The effect is probably related to restricted rotation arou nd the phenyl-O bond that leads to a more rigid core structure.