Optimization of the photo-orientation rate of an azobenzene-containing polymer based on a kinetic model of photoinduced ordering.

The explicit dependence of the rate of photoinduced ordering (photo-orientation) of an azobenzene-containing liquid-crystalline polymer on the photostationary concentration of cis-azobenzene has been predicted theoretically and found experimentally. The employed kinetic model based on the photoinduced rearrangement of the domain structure of a liquid-crystalline material predicts the maximum rate of photo-orientation at ca. 50% content of the cis-isomer in the photostationary state of irradiation.

Direct Observation of Changes in Focal Conic Domains of Cholesteric Films Induced by Ultraviolet Irradiation.

The helical supramolecular structure of cholesteric liquid crystalline (LC) films predetermines their outstanding optical properties and the unique nanostructure of their surface. The introduction of photochromic dopants in these films opens up an interesting possibility for creation of smart cholesteric materials with photocontrollable optical and photovariable surface properties. Using atomic force microscopy (AFM), we performed in situ measurements of the surface topography of cyclosiloxane LC cholesteric oligomer films during the cholesteric helix twisting caused by their preliminary ultraviolet (UV) irradiation.

Surface Relief Changes in Cholesteric Cyclosiloxane Oligomer Films at Different Temperatures.

The development of new approaches for the surface topography control is an important topic as the relief significantly affects physical and chemical properties of surfaces. We studied cholesteric cyclosiloxane oligomeric films on which surface focal conic domains with double-helix pattern were observed by means of AFM. In situ investigation of the dependence of the films topography on temperature showed that the surface relief formation can be effectively managed by varying conditions of thermal treatment.