LANGMUIR-BLODGETT-FILMS OF PHOTOCHROMIC POLYGLUTAMATES .4. SPECTROSCOPIC AND STRUCTURAL STUDIES ON LANGMUIR-BLODGETT-FILMS OF COPOLYGLUTAMATES BEARING AZOBENZENE MOIETIES AND LONG ALKYL CHAINS

Langmuir-Blodgett (LB) films of photochromic poly(5-(4-phenylazo)benzyl L-glutamate-co-5-(4-hexadecyloxy)benzyl L-glutamate) were investigated by means of FT-IR, GIR, and UV-vis spectroscopic methods and by X-ray reflection. A preliminary model for the structure and the structural changes upon irradiation is deduced. The structure is characterized by deformed ''hairy rods'', i.e., with a nonsymmetrical distribution of the side chains around the main chain. The hairy rods are arranged in layers with the main-chain helices preferentially oriented in the dipping direction. The deformation is a result of the interactions at the air/water interface and the surface pressure applied to the monolayer and is retained in the transfer process. The chromophores in the LB film are separated from each other by alkyl chains such that no aggregation occurs. Upon irradiation there are only minor changes in the structure. Upon prolonged irradiation and/or heating of the LB film, a relaxation of the deformed hairy rods toward a more symmetrical distribution of the side chains occurs.