Effect of Dielectric Titanium, Yttrium, and Silicon Oxide Nanoparticles on Electro-Optical Characteristics of Polymer-Dispersed Liquid Crystals

Resumo

Electro-optical characteristics of composite polymer-dispersed liquid crystals doped (implanted) with inorganic SiO₂, TiO₂, and Y₂O₃ nanoparticles in strong electric fields are studied. The composites were obtained by the method of phase separation of liquid crystals (5CB) and polymer (polyvinyl acetate). It is revealed that implantation of up to 1 wt.% of nanoparticles does not noticeably affect the morphology of the composites. The implanted particles change the mismatch between the refractive indices of the polymer and the liquid crystal, and the strong particle aggregation increases the light scattering that can improve the electrooptical contrast of the composites. Changes of the dielectric permittivity with the field are correlated with the light transmittance. It is found that the yttrium and silicon oxides decrease and the titanium oxides increase the Fredericks threshold field. The titanium oxides and to a greater extent the silicon oxides decrease the dependence of the light transmittance on the changes in the dielectric permittivity.