Photochromism of Hemithioindigo Derivatives. II. Photochromic Behaviors in Bilayer Membranes and Related Systems

Photochromic behaviors of hemithioindigo (HT) derivatives in bilayer membrane matrices and related aqueous system are investigated. HT derivatives were incorporated into bilayer membrane matrices at a molar ratio to bilayer amphiphiles of 0.01. Under these conditions, HT amphiphiles having an ammonio group disperse molecularly in the array bilayer membranes, and show the simple photochromism as in the organic solutions. For a HT derivative having no hydrophilic group, on the other hand, irreversible photobleaching proceeds in addition to the photochromic reaction possibly as a result of cluster formation in the bilayer membranes. E-Form conversion at the photostationary state and the E to Z thermal isomerization rate is largely influenced by the crystal to liquid crystal phase transition of the bilayer matrices.