Electro-Optical, Spectroscopical and Morphological Properties of Ultraviolet Cured Polymer/Liquid Crystal Films

The electro-optical behavior of Polymer Dispersed Liquid Crystal (PDLC) films was studied to understand the relationship between the conditions of preparation in terms of the extent of curing, the morphology, and the response to an external electrical field. The PDLC films were prepared by phase separation of a diacrylate/nematic low molecular weight liquid crystal mixture induced by Ultraviolet (UV) curing as a function of irradiation dose. The polymerization/crosslinking process was monitored by Fourier Transform Infrared Spectroscopy (FTIR) in terms of the radiation dose and LC concentration. The conversion of double bonds of the acrylic monomer shows a rapid increase at low dose values followed by a plateau. The transmission vs voltage curves were investigated as a function of wavelength and sample thickness, and show low transmission in the off-state and high transmission in the on-state. The analysis was accomplished by a proper morphology consideration