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E. Schab-Balcerzak

Photoinduced properties of polyesterimides containing azobenzene groups

Polimery 2006, No 7-8, 524


Summary

A series of polyesterimides (PEI) containing photochromic azobenzene groups substituted with either F atom or NO2, CH3 or OCF3 ligands, were presented. They were obtained from various diesterdianhydrides and two amines: 1,3-phenylenediamine or 2,4-diamino-4'-fluoroazobenzene (Scheme B and C). PEI products show good solubility in some typical organic solvents and high glass transition temperature (141-212°C). Elemental analysis, FTIR, 1H NMR and UV-VIS methods have confirmed the chemical structure of the products obtained. Their thermal stability was also determined (by TGA). PEI products showed reversible photoisomerization trans-cis-trans in NMP solutions while exposed to non-polarized light (Hg lamp, λ=365nm) (Fig. 1, Scheme A). Exposure to polarized light (laser Ar+, λ=488nm) caused reorientation of the azobenzene groups what led to induction of optical anisotropy in the initially isotropic polymers. Photoinduced optical anisotropy in PEI films was examined by calculation of the value of dichroism generated (Fig. 3 and 4). The value of photoinduced dichroism (D) were in the range of 0.12-0.26. Photoinduced properties of the polymers were considered dependently on their chemical structure i.e. the kind of substituent in the azobenzene group and on the part of these groups in a polymer unit. The polymers with nitric substituent showed the biggest D values. However, no effect of introduction of the next azobenzene group to PEI mer was observed. Preliminary investigations of ability of selected polymeric films to formation of holographic networks (laser Ar+, λ=514.5nm) were carried out. It was found that this phenomenon was reversible (Fig. 6).


Key words: polyesterimides, photoisomerization, substituted azobenzene chromophores, photoinduced dichroism, formation of holographic network


e-mail: ewabalce@cchp-pan.zabrze.pl


E. Schab-Balcerzak

Photoinduced properties of polyesterimides containing azobenzene groups