Photo-controlled diffusion in reacting liquid crystals: A new tool for the creation of complex molecular architectures

Diffusion enforced photo-assembling during polymerization of a chiral-nematic monomer blend yields a cholesteric network in which the helical pitch gradually changes over the cross-section of the film. The polarization selective reflection band of cholesterics can be made much wider than those of single pitch materials and may expand over the whole visible wavelength. The paper discusses the photo-controlled diffusion process in thin films, the important process parameters and some of the properties of the molecular architectures obtained.