Competition of alignment and aggregation? Phenomena in constrained films of LC poly(olefin ulfone)s and maleic anhydride co- and terpolymers

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 isotropi c spin-coated films annealing results in homeotropically aligned films by s pontaneous self-assembling. X-ray specular scattering (XRS) and X-ray grazi ng incidence diffraction (GIXD) indicate a layered structure across the fil m parallel to the interface and significant in-plane order in thin films. P olarised UV-VIS spectroscopy investigations show that the homeotropic orien tation of the side groups causes the formation of "card packed" or H-aggreg ates. For azobenzene containing MAC terpolymer an initial UV-irradiation fo llowed by a polarised VIS-irradiation causes a light-induced co-operative r eorientation of both types of side-groups and results in a lamellar stackin g which is tilted. Orientation and aggregation are therefore driven by the liquid crystallinity and the segregation tendency of POS and MAC in constra ined films. This seems to be an important factor for such spontaneous order ing processes.