Control of the microstructure of polymer network and effects of the microstructures on light scattering properties of UV-cured polymer-dispersed liquid crystal films

Polymer-dispersed liquid crystals (PDLC) films were prepared from ultraviolet (UV) irradiation-induced polymerization of the photopolymerizable monomers in photopolymerizable monomers/nematic liquid crystal (LC) mixtures. The effects of the composition of the mixtures, the curing temperature, and the UV light intensity on the microstructure of the polymer network in the PDLC films were investigated. Furthermore, the effects of the microstructures on the light scattering properties of the PDLC films in the wavelength region of 300-2500 nm were studied experimentally and theoretically based on the combination of three kinds of classical light scattering theories: the Rayleigh-Gans (RG) approach, the anomalous diffraction (AD) approach, and the geometrical optics (GO) approach. It was found that the sizes of LC domain in PDLC films increased with the increase of the LC content as well as the decrease of the UV curing intensity, while increased at first and then decreased with the increase of the curing temperature. Moreover, smaller LC domain sizes could exhibit strong scattering properties in a smaller VIS wavelength region and the transmittance in NIR region (especially in the wavelength range of 1300-2500 nm) obviously decreased with the increasing sizes of LC domain. (C) 2008 Wiley Periodicals, Inc.