Studies on Nematic Liquid Crystal Composite Langmuir Blodgett Films: Effects of SiO2 Nano-Particles

Abstract

Langmuir Blodgett monolayers of eutectic nematic liquid crystal and its mixture with polyvinyl alcohol (PVA) capped SiO2 nanoparticles were deposited on quartz substrate in Y-type mode. PVA capped SiO2 nanoparticles were characterized by Fourier Transformation Infrared Spectroscopy (FTIR). Surface pressure-area isotherm profiles were studied for each monolayer, as various phase changes were observed during constant compression of barriers. The Langmuir monolayer of nematic liquid crystal mixture showed hysteresis during multiple isotherms because of the mixed amphiphilic nature of nematic liquid crystal molecules while PVA capped SiO2 nanoparticles showed no hysteresis during isotherm cycles due to elastic nature of the polymer. Elasticity profile of monolayer has been studied as a function of mean molecular area (MMA). Normalized area profiles decrease constantly with time ensuring about constant film compression. Equilibrium stabilized surface pressure (ESP) was attained during each deposition. Topography of monolayer has been investigated through Atomic Force Microscope (AFM).