Switchable Gratings from Polymerized Nematic Emulsions

• Published in: Advanced functional materials 2001-12, Vol.11 (6), p.457-460
• Main Authors: De Filpo, G., Nicoletta, F. P., Macchione, M., Cupelli, D., Chidichimo, G.
• Format: Article
• Language: English
• Subjects: Emulsions; Liquid crystals; Liquid crystals, polmer dispersed; Phase separations; polmer dispersed
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/1616-3028(200112)11:6<457::AID-ADFM457>3.0.CO;2-H

Permanent diffraction gratings can be built in polymer dispersed liquid crystals by using either photomasks or crossed laser beams, in order to modulate the light intensity across the film during the curing process. The intensity of light diffracted from these gratings can be controlled with an applied electric field. In this paper, we report our results on the formation of permanent gratings in nematic emulsions, photopolymerized through a photomask. The gratings are permanently stored and the diffraction efficiency can be modulated with an electric field. The grating structure has been investigated by optical and scanning electron microscopy. The advantages of using nematic emulsions in photopatterning are discussed. Electrically switchable gratings have been built from nematic emulsion films via an easy two‐step photopolymerization. In the first step the substrate is partially covered by a photomask, affording an array of liquid crystal (LC) droplets within a polymer matrix (see Figure). Nematic emulsions allow control of the reaction by varying the temperature and monomer/LC ratio, and yield low‐price devices controllable by weak electric fields.