Polymer dispersed liquid crystals

Low molar mass liquid crystals (LCs) are typically not soluble in polymer systems to any great degree. When the two different materials are mixed, this leads to two-phase systems whose morphology depends on a variety of factors including, primarily, the concentration. The resulting two-phase structures can have inclusions with nanometer through macroscopic dimensions. Although there are a large number of variants, these structures are generically called 'polymer dispersed liquid crystals' (PDLCs) when the resulting morphologies lead to systems that scatter light. This is often achieved in the intermediate concentration region (30-70% LC), in which morphologies with large mesoscale inclusions are typically formed. If the refractive index matching is done correctly, upon application of an electric field, the scattering can be turned off by an electric field, leading to dynamic transparency. This is a review of past literature with a focus on the type of morphologies that can be exhibited. Basic electro-optic properties are discussed as is the large variety of morphologies that can be induced. Also included is the related research area of 'periodic' PDLC systems, wherein the phase separation process is induced spatially. This leads to anisotropic systems where an electric field can control diffraction, instead of scattering.