Kinetics of photoisomerization and time evolution of ordering in azobenzene-containing materials are studied theoretically and by using computer simulations. Starting from kinetic equations of photoisomerization, we show that the influence of light is equivalent to the action of the effective potential, which reorients chromophores perpendicularly to polarization direction. The strength of the potential is defined by optical and viscous characteristics of the material. The potential generates photomechanical stress of giant values ∼GPa, in accordance with recent experimental findings for azobenzene materials deep in a glassy state. The proposed approach has a great predictive strength for deeper understanding and further development of the photocontrollable smart compounds.