Reorientation of liquid-crystal (LC) molecules in mixed surfactant/LC Langmuir films

Abstract The molecular orientation of 4- n -octyl-4′ -cyanobiphenyl (8CB) liquid crystal molecules in a pentadecanoic acid (PDA) surfactant matrix at the air—water interface is studied with the use of optical second-harmonic generation. The results indicate a significant reorientation of the biphenyl core upon compression of the films, due to interactions between the PDA and 8CB molecules. The final molecular orientation is consistent with that of a fully stretched perpendicularly aligned alkyl chain of the LC molecules.