Light-scattering analysis of the temperature-dependent transmittance of a polymer-dispersed liquid-crystal film in its isotropic phase

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Abstract
We have measured the temperature-dependent transmittance of a polymer-dispersed liquid-crystal (PDLC) film in its isotropic phase. We show that the measured transmittance can be quantitatively described within experimental error over a wide temperature range using Rayleigh-Gans light-scattering theory with film parameters previously determined from refractive-index studies and scanning electron microscopy; no freely adjustable parameters or normalization constants are necessary to describe the measured transmittance data. We obtained equally good agreement between theory and experiment regardless of whether or not we included droplet correlation effects in our transmittance calculations. The precision with which the refractive index of the matrix material in a cured PDLC film can be determined is the main factor preventing us from quantitatively assessing the role of droplet correlation effects in PDLC films at this time. We have also compared the transmittance characteristics of our PDLC film with the published transmittance of a film composed of liquid crystal in the pores of a solid matrix. We find that the published results are consistent with the form of the equations of scattering theory; however, quantitative agreement between measured and calculated transmittance would require film parameters different from those published.