Thermophysical and thermomechanical properties of Norland Optical Adhesives and liquid crystal composites

Thermophysical and thermomechanical properties of UV-cured Norland Optical Adhesives (NOA65) and low molecular weight Liquid Crystal E7 systems were investigated. Thin films of Polymer Dispersed Liquid Crystal were prepared by Polymerization Induced Phase Separation and UV-curing. Phase diagrams were established using Polarized Optical Microscopy and DSC to determine the lines of nematic to isotropic phase transition as well as the glass transition temperature changes with the system composition. Mechanical measurements were performed in the static and dynamic modes to determine the moduli in terms of the curing time, the temperature and the amount of low molecular weight liquid crystal molecules. Thermomechanical measurements were found to overestimate the glass transition temperature as compared to calorimetric data. Variations of the Young's modulus and the molecular weight defining the mesh size of the network were analyzed in terms of the curing time and liquid crystal concentration. (C) 2008 Wiley Periodicals, Inc.