Photoorientation in Lb Multilayers of Thermotropic Polymers

Abstract

The photoreorientation of azobenzene side groups is studied in LB multilayers of different order and compared to the process in spin-coated films of the same smectic polyacrylate and “hairy rod” polyglutamates. The photochemically induced reorientation process depends on the aggregation of the azobenzene moieties, the supramolecular order of the films, the enthalpic stability of the mesophase in the case of the LB multilayers of thermotropic polyglutamates and on the irradiation conditions. The stable nematic-like order of the “hairy rod” polyglutamate backbones influences the photoreorientation of the azobenzene side groups in the LB films. In all cases the photoreorientation process becomes more efficient after weakening the intermolecular interactions by a suitable preparation of the films, on irradiation in the viscous-elastic state or by a temporary photochemical decoupling of the supramolecular order.