Photochemical switching between colloidal photonic crystals at the nematic-air interface

• Published in: Physical review. E, Statistical, nonlinear, and soft matter physics Vol. 78; no. 2 Pt 1; p. 020701
• Main Authors: Lev, B, Chernyshuk, S B, Yamamoto, T, Yamamoto, J, Yokoyama, H
• Format: Journal Article
• Language: English
• Published: United States 01.08.2008
• ISSN: 1539-3755
• DOI: 10.1103/physreve.78.020701

A direct observation of the photochemical switching between colloidal crystals with different lattice constants in a liquid-crystal (LC) emulsion is reported. Glycerol droplets introduced in a nematic liquid crystal form two-dimensional hexagonal colloidal crystal at the nematic-air interface with a lattice constant depending on the surface tension sigmaLCA. We dope an azobenzene derivative into the LC emulsion to modulate the colloidal structures by using cis-trans photoisomerization of the doped dye. The photoisomerization changes sigmaLCA and the lattice constant of colloidal crystals with a relaxation time T approximately 10s . A simple theoretical description, which qualitatively agrees with experimental results, has been proposed. Possible applications in infrared range photonic crystals are discussed. The number of different kinds of dyes N set the number of different possible photonic crystals as 2N, which may be transformed one into another by corresponding 2N light beams inducing cis-trans photoisomerization of the doped dyes.