Photoisomerization Processes of Azobenzene Compounds in Thin Poymer Films

Abstract

One of the most important properties of the molecular switches is turning of a molecule by external action, e.g. by irradiation with light of definite wavelength. The molecules of promise for the molecular switches are those with azobenzene moiety. When azobenzene is irradiated with light of definite wavelength, it is possible to observe the process of trans/cis isomerisation. In this work, the influence of photoisomerisation processes on the changes in the surface potential of a novel azobenzene compound is investigated.We have studied the surface potential of a PMMA polymer film with polar azobenzene derivative of different concentrations. To orient azobenzene molecules in the film the corona poling method was used, and for studying the surface potential variations -the Kelvin probe method. The photoreaction time constant of the fast response (several seconds) was found to be almost independent of the molecular concentration in the polymer film and of the absorbed light intensity in the bulk of a sample. In contrast, the amplitude of photoinduced changes in the surface potential depends both on the concentration of azobenzene molecules and on the absorbed light intensity in bulk of the host-guest polymer film.

Optically Induced Surface Relief Gratings in Polymer Films Doped With Sulphonyl Group Containing Azobenzene

“…The azobenzene molecules A-45 and A-48 have strong dipole moments − both in trans-and cis-isomers. According to the RHF ab initio calculations with the basis set 6-31G** by Gaussian G09W software package, the dipole moment of an azobenzene A-45 trans-isomer is 5.11 D, and that of a cis-isomer − 7.14 D [7]. This means that such dipoles tend to associate and could make aggregates in a polymer matrix.…”