Molecular alignments in liquid crystal mixtures of 8CB with 10CB determined by scanning tunneling microscopy

We observed the specific structures of molecular alignments in the liquid crystal mixtures of n-alkylcyanobiphenyl (mCB: m=8 and 10) on highly oriented pyrolytic graphite (HOPG) substrates by scanning tunneling microscopy (STM). The alignment structures, which were quite different from previously reported alignments for each monophase 8CB and 10CB, showed two different alignments and packings of both molecules depending on the mixing rate of 8CB and 10CB. One was observed in a mixture with a rather low mixing rate of 8CB in 10CB, in which the unit structure was composed of two 8CB molecules and four 10CBs with bilayer conformations. The other was a unit structure that consisted of four 8CBs and of six 10CBs in the mixture with a rather high mixing rate of 8CB. No other combination was observed.