Liquid crystalline behaviour of photochromic LB multilayer films

Amphotropic copolymers containing rod-like side groups combine the ability to form Langmuir-Blodgett multilayer assemblies with thermotropic liquid crystalline self-organization on temperature changes. Photochromic azobenzene side groups hereby affect the supramolecular structure of LB multilayer structures in dependence on irradiation wavelength and polarization of the incident light beam as well as on temperature. A phase transition from the constrained LB film into a liquid crystalline like layer structure can be easily reached upon annealing at a temperature where the bulk polymer performs a smectic liquid crystalline phase and/or different irradiation procedures. Thus, changes in the structure of LB multilayers of the observed copolymers were studied in dependence on temperature within the existence range of different glassy, crystalline and liquid crystalline states by means of energy-dispersive small angle X-ray scattering and X-ray grazing incidence diffraction using synchrotron radiation due to the excellent compatibility with the observed polymer materials and the measuring problems.