Competition of Alignment and Aggregation? Phenomena in Constrained Films of LC Poly (Olefin Ulfone)s and Maleic Anhydride Co- and Terpolymers

Abstract

Anisotropic films of functionalised polymers such as the liquid crystalline poly (olefin sulfone)s (POS) and maleic anhydride co- and terpolymers (MAC, containing azobenzene side-groups too) are studied. Starting from isotropic spin-coated films annealing results in homeotropically aligned films by spontaneous self-assembling. X-ray specular scattering (XRS) and X-ray grazing incidence diffraction (GIXD) indicate a layered structure across the film parallel to the interface and significant in-plane order in thin films. Polarised UV-VIS spectroscopy investigations show that the homeotropic orientation of the side groups causes the formation of “card packed” or H-aggregates. For azobenzene containing MAC terpolymer an initial UV-irradiation followed by a polarised VIS-irradiation causes a light-induced co-operative reorientation of both types of side-groups and results in a lamellar stacking which is tilted. Orientation and aggregation are therefore driven by the liquid crystallinity and the segregation tendency of POS and MAC in constrained films. This seems to be an important factor for such spontaneous ordering processes.