Temperature Dependence of Flow Alignment in Nematic Liquid Crystals

The temperature dependence of the flow alignment angle has been measured in two nematic liquid crystals, $p^{\prime }$-methoxybenzylidene-$p-n$-butylaniline and $p-n$-hexyloxybenzylidene-$p^{\prime }$-aminobenzonitrile. For both compounds this angle reaches a peak value at the nematic-isotropic transition point. Experimental evidence is reported for the first time that flow alignment does not occur over the entire mesophase of certain nematics.