Photoreactive Langmuir–Blodgett–Kuhn multilayer assemblies from functionalized liquid‐crystalline side chain polymers, I. Homopolymers containing azobenzene chromophores

Abstract

Abstract Stable monomolecular layers of a liquid‐crystalline homopolymer bearing azobenzene chromophores in the mesogenic side groups could be prepared at the water–air interface by slow compression at room temperature. From the area per monomer unit of A 0 ≈0.25 nm 2 a structural model with tightly packed azobenzene groups oriented nearly parallel to the surface normal was deduced. After transfer to a solid support in a Y‐type mode the obtained Langmuir–Blodgett–Kuhn (LBK) multilayer assemblies of varying thicknesses (from a double layer to a thick film of d = 238 nm, capable of guiding optical modes) were prepared and analyzed by X‐ray reflection and optical evanescent wave techniques. A monolayer thickness of d 0 = 2.52 nm, as well as the anisotropic index of refraction of these layers, could thus be evaluated. Photo‐isomerization by UV‐irradiation (at λ = (360±30)nm) was examined by UV‐VIS absorption spectroscopy. X‐ray reflectivity data of samples illuminated for 30 min showed a complete loss of the layered structure of the LBK samples. As a result strongly light‐scattering films were obtained. Surface plasmon microscopy was used to demonstrate the usefulness of this photo‐induced order–disorder transition for optical information storage.