Chiral nematic order in liquid crystals imposed by an engineered inorganicnanostructure

Control over the orientational order of liquid crystals (LCs) is critical t o optical switching and display applications. Porous polymer networks have been used to influence the orientation of embedded chiral liquid crystals(1 ), yielding for example reflective displays. Here we show that inorganic fi lms with a porous structure engineered on the submicrometre scale by glanci ng-angle deposition(2,3) can be used to control the orientation of LCs impr egnated into the voids. The inorganic material contains helical columns tha t orient rod-like nematic LCs into a phase similar to a chiral nematic(1,4) but with direct control of the local molecular arrangement (for example, t he helical pitch) imposed by the inorganic microstructure. We also show tha t reactive LC molecules in this composite material can be crosslinked by ph otopolymerization while retaining the imposed structure.