REORIENTATION OF LIQUID-CRYSTAL (LC) MOLECULES IN MIXED SURFACTANT LCLANGMUIR FILMS

The molecular orientation of 4-n-octyl-4'-cyanobiphenyl (8CB) liquid-c rystal molecules in a pentadecanoic acid (PDA) surfactant matrix at th e air-water interface is studied with the use of optical second-harmon ic generation. The results indicate a significant reorientation of the biphenyl core upon compression of the films, due to interactions betw een the PDA and 8CB molecules. The final molecular orientation is cons istent with that of a fully stretched perpendicularly aligned alkyl ch ain of the LC molecules.