We describe a new polymer patterning technique that produces controllable morphological and optical anisotropy in a polymer network. This technique is based on the use of pattern-forming states of nematic and cholesteric liquid crystals as templates for forming ordered polymer networks. One and two-dimensional optical patterns are induced by applying an electric field across a narrow gap of an electro-optical cell. These field-induced optical patterns are then stabilized by UV-induced polymerization of a typically 5 wt% reactive monomer in liquid crystal host. Depending on specific conditions (e.g., thickness to pitch ratio of a cholesteric, applied electric field, and wavelength of UV illumination), the polymer captures various degrees of the orientational order and spatial periodicity of the pattern-forming states of liquid crystals. The fidelity of the templating effect is explored using polarizing optical microscopy and SEM. We also describe the effect of UV wavelength on the network morphology and the morphological control over the "third" dimension (normal to the cell substrates).
Advances in Liquid Crystalline Materials and Technologies
Copyright 2002 Materials Research Society. Available on publisher's site at http://www.cambridge.org/th/academic/subjects/engineering/series/mrs-proceedings.