Langmuir-Blodgett (LB) films of poly (5-(2-(4-((4-hexylphenyl)azo)phenoxy)ethyl) L-glutamate) (P2) and poly (5-(6-(4-((4-hexylphenyl)azo)phenoxy)hexyl) L-glutamate) (P6) polymers with a stiff backbone and flexible side chains ("hairy rods"), have been investigated at different steps of the photoisomerization and annealing process by means of X-ray reflection and U V-vis spectroscopy. From the absorption spectra the amount of aggregated chromophores was estimated using a peak-fitting procedure. The original LB structure, which is characterized by deformed "hairy rods" arranged in bilayers, is destroyed upon photoisomerization or annealing. The side chains relax to a more symmetrical distribution around the main chain helix. Furthermore the aggregation of the chromophores as well as their orientation in respect to the main chain helix is changed. The changes are more pronounced upon irradiation and depend on the length of the spacer used to tether the chromophores to the polymer backbone.

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The paper presents a study of the evolution of the tilt angle with time in ''command-surface'' liquid crystal cells under irradiation with UV light. In these cells, the liquid crystal orientation can be switched via a photoinduced isomerization of azo moieties attached to the surface. The trans and the cis state induce homeotropic and homogeneous alignment, respectively. Polymeric systems assembled with the Langmuir-Blodgett ͑LB͒ technique were employed. Not only homeotropic and homogeneous alignment, but also tilted alignment is found. The azimuthal direction of tilt is given by the dipping direction during LB transfer. In order to study the underlying microscopic mechanisms, we investigated the switching kinetics, performed in situ evanescent UV-visible spectroscopy, and measured the anchoring energy. The material parameters of both the command layer and the liquid crystal were systematically varied. The well defined azimuthal direction of tilt is ascribed to packing anisotropies in the command layer induced during LB transfer. The polar tilt angle is determined by the competition between interfacial entropy, on the one hand, which favors mixing and thereby homeotropic alignment, and a polar interaction, on the other hand, favoring homogeneous alignment.

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