We investigated the effects of the different content ratios of 2-ethylhexylacrylate (2-EHA) and 2-ethylhexylmethacrylate (2-EHMA) on the relationships among the photopolymerization rate, morphology of liquid crystals (LCs) droplets, and electrooptical properties of trifunctional urethane acrylate-based polymer-dispersed liquid crystal (PDLC) systems. Photo-differential scanning calorimetry (DSC) analysis and resistivity measurement revealed that increasing 2-EHMA content gradually decreased the photocure rate of trifunctional urethane acrylate-based PDLCs, which prolonged the phase separation between the LC molecules and the prepolymers. Morphological observations and electro-optical measurements demonstrated that trifunctional urethane acrylate-based PDLCs with the 2-EHA:2-EHMA ratios from 4:1 to 3:2 in weight percent formed the favorable microstructures of LC droplets being within the range of 1-5 mm to scatter light efficiently and showed the satisfactory off-state opacity and on-state transmittance and the relatively low-driving voltage. The microstructures of LC droplets and electro-optical properties of trifunctional urethane acrylatebased PDLCs could be usefully optimized by controlling the photocure rate using the different 2-EHA/2-EHMA content ratios.

We synthesized tetrafunctional allyl ether monomer (4-AE) and investigated the effects of the different molar ratios of trimethylolpropane tris-(3-mercaptopropionate) (3-SH) to 4-AE on the photopolymerization behavior, morphology, and electro-optical properties of thiol-ene-based PDLC films. Photo-DSC and DSC analyses revealed that the PDLC sample containing 45 wt% 3-SH and 45 wt% 4-AE gave the highest exotherm, the fastest photocure rate, and the highest T g due to the matched stoichiometry. Morphological observations and electro-optical measurements showed that the PDLC sample with the matched molar ratio gave the smallest LC droplet size, the highest threshold, driving voltages, and lowest saturation transmittance because the orientation of LC molecules got difficulty in small droplets. The stoichiometric ratios of 3-SH to 4-AE played an important role in controlling the photocure rate, phase separation rate, microstructures of LC droplets, and electro-optical properties of thiol-ene-based PDLC systems.