LANGMUIR-BLODGETT-KUHN MULTILAYERS OF POLYGLUTAMATES WITH AZOBENZENE MOIETIES - INVESTIGATIONS OF PHOTOINDUCED CHANGES IN THE OPTICAL-PROPERTIES AND STRUCTURE OF THE FILMS

Langmuir-Blodgett-Kuhn (LBK) multilayer assemblies of ''hairy-rod'' po lyglutamates with stiff main chains and flexible side chains containin g photochromic azo units exhibit a highly optically anisotropic struct ure when the azo molecules are in the trans form and a nearly opticall y isotropic structure when the azo molecules are in the cis form. The trans <-> cis photoisomerization of the azo molecules switches them be tween a highly oriented trans cofiguration and a bend cis configuratio n, thus turning the anisotropy ''on'' and ''off''; the corresponding o ptical order parameter changes by about 1 order of magnitude. In contr ast to spun-cast polymer films containing azobenzene units, photoselec tion under polarized light irradiation does not occur in these LBK str uctures. The study of the electronic density distribution of these fil ms shows that-a remarkable variation in the LBK structures' stability comes with a seemingly small change in the side-chain structure. A sta ble LBK double-layer structure has been prepared, and its physical ori gin has been discussed.