Liquid crystalline polymeric ferroelectric properties

To produce novel LC phase behavior and properties, a variety of polymer/LC composites have been developed. These include systems which employ liquid crystal polymers (5), phase separation of LC droplets in polymer dispersed liquid crystals (PDLCs) (4), incorporating both nematic (5,6) and ferroelectric liquid crystals (6-10). Polymer/LC gels have also been studied which are formed by the polymerization of small amounts of monomer solutes in a liquid crystalline solvent (11). The polymer/LC gel systems are of particular interest, rendering bistable chiral nematic devices (12) and polymer stabilized ferroelectric liquid crystals (PSFLCs) (1,13), which combine fast electro-optic response (14) with the increased mechanical stabilization imparted by the polymer (75). 

Flexible spacers in the semirigid-rod molecule allow the molecule to orient with order parameter greater than 0.8 when coated and cured upon a rubbed polyimide layer. Kinetics of the photo-polymerization [62,63] and surface-induced orientation [49] as well as mechanical [64,65], optical [59,66,67], and ferroelectric properties [68-70] of the anisotropic networks were thoroughly examined. These investigations were mainly carried out by the Philip s research group and were applied to develop liquid crystalline display devices [58,69]. 

Cross-linked polymeric liquid crystals offer a wide variety of unique and in-tere.sting properties. Because of the interaction between the mesogens and the network backbone in liquid crystal elastomers, mechanical deformations can align the director, and these materials are piezoelectric. Industrial applications of liquid crystalline thermosets are driven by additional properties such as toughness, a tunable coefficient of thermal expansion, ferroelectricity, and nonlinear optical properties. Reviews on this topic are given by Barclay and Ober [4] and by Warner and Terentjev [5]. 

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