Effect of a Photopolymerizable Monomer Containing a Hydrogen Bond on Near-Infrared Radiation Transmittance of Nematic Liquid Crystal/Monomers Composites

Abstract

Polymer dispersed liquid crystal (PDLC) films were prepared by ultraviolet (UV) radiation induced polymerization of photopolymerizable monomers in nematic liquid crystal (LC)/monomers composites. The effect of a photopolymerizable monomer 2-hydroxyethylmethacrylate (HEMA) containing a hydrogen bond on the transmittance of the PDLC films in the wavelength region of 300−2500 nm was investigated by UV−visible (VIS)−near-infrared (NIR) spectrophotometers, scanning electron microscopy, and an infrared spectrometer. It was surprisingly found that the addition of a small amount of HEMA monomer containing a hydrogen bond could dramatically decrease the off-state transmittance in the NIR region partially due to the formation of a compact and thick-border polymer network. Then the conceivable mechanism concerning the effect of HEMA monomers containing a hydrogen bond on the microstructure of the polymer network was investigated experimentally and theoretically. This provided a potential approach for the electrically controlled modulation of NIR radiation.