Electrooptic studies on polymer-dispersed liquid-crystal composite films. III. Poly(methyl methacrylate-co-butyl acrylate)/E7 and poly(methyl methacrylate-co-butyl acrylate)/E8 composites

Composite films composed of poly(methyl methacrylate-co-butyl acrylate) (PMMABA) and nematic-type liquid crystals E7 and E8 (commercial products from E. Merck, Darmstadt, Germany) were prepared through solvent casting in chloroform. The morphology and electrooptic responses were studied. Scanning electron microscopy observations showed that the liquid-crystal phase (E7 or E8), as larger, elongated, interconnected cavities, was continuously embedded in a spongelike PMMABA matrix. At a specific level of the liquid-crystal (E7 or E8) loading (30/70 wt %), the effects of the voltage, temperature, and frequency of an applied alternating-current electric field on the transmittance of the composite films were measured with a He-Ne laser (wavelength = 632.8 nm). The results were interpreted in terms of the aggregation structure, interfacial interaction, and solubility of the liquid crystal in the matrix polymer. The results indicated that, under these experimental conditions, the output could be controlled to a desired level by the selection of suitable liquid crystals to prepare polymer-dispersed liquid-crystal, electrooptic, active composite films with a response time of the order of only milliseconds or less. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008