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)benzy l L-glutamate-co-5-(4-hexadecyloxy)benzyl L-glutamate) were investigat ed by means of FT-IR, GIR, and UV-vis spectroscopic methods and by X-r ay reflection. A preliminary model for the structure and the structura l changes upon irradiation is deduced. The structure is characterized by deformed ''hairy rods'', i.e., with a nonsymmetrical distribution o f the side chains around the main chain. The hairy rods are arranged i n layers with the main-chain helices preferentially oriented in the di pping direction. The deformation is a result of the interactions at th e air/water interface and the surface pressure applied to the monolaye r and is retained in the transfer process. The chromophores in the LB film are separated from each other by alkyl chains such that no aggreg ation occurs. Upon irradiation there are only minor changes in the str ucture. Upon prolonged irradiation and/or heating of the LB film, a re laxation of the deformed hairy rods toward a more symmetrical distribu tion of the side chains occurs.