A transient phase separated structure during the photo-polymerization induced-phase separation process of liquid crystal/polymer composites consisting of a continuous phase of nematic liquid crystal and a three-dimensional polymer network was successfully observed by interrupting UV light irradiation for photo-polymerization. Those transient composites were characterized by a difference in temperature for nematic-isotropic transition point (Tn-i) of the liquid crystal phase, a comparison of morphology for polymer phase between an initial stage and the last stage of phase separation, and an electro-optical performance at each period of phase separation process. It was found that the composite even at an initial stage of phase separation showed a transparent-turbid (light scattering) operation with an electric field and the UV irradiation period required to attain the final voltage-transmittance curve accorded well with that to give a saturation of Tn-i of the liquid crystal phase. A schematic diagram for photo-polymerization induced-phase separation process was proposed according to investigation into characteristics of the liquid crystal/polymer composites having a transient phase separated structure.
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