Chiral nematic order in liquid crystals imposed by an engineered inorganic nanostructure

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