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The model of the rotational diffusion of the azo-dye molecules under the action of polarized uv light was used to explain the formation of the photoinduced order in azo-dye layers. We consider both the approximations of negligible and strong molecular interaction during the process of the reorientation under the field of a polarized light. We constructed an experimental setup, based on a photoelastic modulator, that allows accurate in situ measurements of the phase retardation ␦ of thin film as a function of the exposure time t exp and exposure power W ͑W/cm 2 ͒. A good agreement with experiment was observed. Fitting the experimental curves ␦͑t exp ͒ for different power values W, we can estimate the coefficient of rotational diffusion D, azo-dye order parameter S͑t exp ͒, and other parameters of the rotational diffusion model.

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Force-distance curves were obtained using a home-built atomic force microscope (AFM) at different temperatures (T ) 30-65°C) and probe rates (f ) 31.25-50 000 Hz) on a 150 nm thick film of a model sample, poly(tert-butyl acrylate) (M w ) 148K Da, Mw/Mn ) 17, and Tg bulk ) 50°C according to DSC). The pull-off force, Fad, at which detachment between the AFM tip and the sample occurred was measured as adhesion. By limiting the loading force, F, to ∼2.5 nN, the tip penetrated by no more than 2 nm into the sample in the glassy state. Therefore, evolution of the rheological properties of the polymer at the free surface with increasing T could be studied. In the vicinity of Tg bulk , Fad was seen to increase rapidly with increasing T or decreasing f. Equivalence between T and f was found using time-temperature superposition in which, upon rescale of f by a temperature-dependent shift factor aT AFM (T), a master curve Fad(aT AFM (T) f) resulted. We showed that Fad(aT AFM (T)f) could be fully accounted for by using an approach based on fracture mechanics of viscoelastic solids. No noticeable enhancement in the surface relaxation could be deduced according to our findings.