Effects of the composition and nematic–isotropic phase transition on the electro‐optical responses of unaligned polymer‐dispersed liquid crystals. I. Composites of poly(methyl methacrylate) and E8

Composite films composed of poly(methyl methacrylate) (PMMA) and the nematic‐type liquid crystal (LC) E8 were prepared by solution casting in chloroform. The electro‐optical performance characteristics were studied for a wide range of PMMA/E8 compositions (10–80 wt % E8). At two specific levels of LC (70 and 80 wt %), the effects of temperature, voltage, and frequency of the applied electric field on the optical transmittance of films were extensively measured with a He–Ne laser (λ = 632.8 nm) as a light source. Scanning electron microscopy observations showed the formation of large E8 droplets in PMMA due to phase separation, and the homogeneous distribution increased with increasing E8 content. The results were interpreted in terms of aggregation structure, interfacial interaction, LC loading, and the solubility of LC in the polymer matrix. The results obtained indicate that under the experimental conditions imposed, the output could be continuously controlled to the desired level by the selection of a suitable loading of LC to prepare polymer‐dispersed LC electro‐optical active composite films with response times on the order of only a few milliseconds.