Novel azobenzene-containing polyamic acids as Langmuir-Blodgett-Kuhn multilayer films and for liquid crystal alignment switching

New azobenzene-containing polyamic acids (PAAs) with systematically tailored architectures were synthesized and assembled as Langmuir-Blodgett-Kuhn (LBK) multilayers. Surface plasmon resonance (SPR) spectroscopy was employed to measure the film thickness and its dependence upon the number of layers deposited. The pronounced Bragg peak in the X-ray reflectivity scans indicated the films' regularly repeated internal layer structure. Photoisomerization studies confirmed the excellent reversibility of the trans-cis and cis-trans isomerization reactions of the azobenzene sidegroups within the multilayer structures. Further, these films were found to be able to switch the orientation of liquid crystalline layers between homeotropic and planar alignment by the reversible photoisomerization of the azobenzene moieties.