INFLUENCE OF PHASE AND CHAIN-LENGTH OF LIQUID-CRYSTALS ON WETTING PHENOMENA OF GRAPHITE

Several homologous series of liquid crystalline compounds were used to investigate wetting on the basal plane of highly oriented pyrolytic graphite at different temperatures. The wetting behavior was independent of the chemical structure of the rigid core segment or the polar head group. Within a particular homologous series, compounds with a long alkyl chain showed complete wetting in the nematic or cholesteric phase. The same compounds in the isotropic phase exhibited partial wetting. Partial wetting was observed on those with no chain or short chains in both nematic (cholesteric) and isotropic phases. A model of the wetting mechanism on the graphite surface by a liquid crystalline compound with an alkyl chain is suggested.