ИСТИНА

Photoorientation, photofluidization and photoinduced mass-transfer processes observed in polymer and low-molar-mass materials attract a great attention due to the promising potential for application in holography, optoelectronics, as well as for the creation of different nanodevices, microlasers, etc. In this work photooptical properties of films of two novel azobenzene-containing LC polymethacrylates were studied: A special attention is focused on the investigations of the photoinduced processes under polarized light action and influence of LC state on these processes. Two different phenomena were investigated: irradiation by polarized unfocused light results in orientation of chromophores in direction perpendicular to the polarization plane; on the other hand, irradiation by highly focused laser beam induces mass transfer processes. The presence of the lateral methyl substituents in azobenzene chromophores causes extreme increase in their photosensitivity in comparison with nonsubstituted analogues. Thus, irradiation even with red light (633 nm) induces photoorientation process and enables to uniaxially align chromophores. The effect of the highly focused green (532 nm) and red (633 nm) laser light on the surface topography of the films was investigated. It is shown that focused polarized green light irradiation induces craters formation in the polymer films (Fig. 1a), whereas red laser beam leads to completely different behaviour, i.e. to the formation of the hills (Fig. 1b). The observed mass-transfer process is polarization sensitive and occurs in the direction along the polarization plane of the laser beams. Possible mechanisms of the observed photoinduced phenomena have been suggested and discussed.