Helical pitch dependence of the electro-optic characteristics in polymer/cholesteric liquid crystal nanocomposites

The helical pitch (p) dependence of the electro-optic characteristics in low monomer concentration polymer/cholesteric liquid crystal (PChLC) nanocomposites is reported. Four mixtures with different helical pitches were prepared by mixing a ChLC and a mesogenic monomer with a photoinitiator, and polymerized at room (20 °C) or low (−20 °C) temperatures to fabricate samples exhibiting the 'polymer-stabilized' and 'deformation-free' responses, respectively. Reflecting the difference in the electro-optic response modes, the threshold electric field showed different dependencies on the helical pitch. The 'polymer-stabilized' PChLCs showed a p-0.57 dependence on the pitch, which is a consequence of the response being dominated by the Helfrich deformation. The 'deformation-free' samples, on the other hand, showed a smaller dependence on pitch of approximately p-0.33. The decrease in the pitch dependence is described as a consequence of the nano-confined LC molecules undergoing a Fredericks-type reorientation instead of a helix deformation.