Synthesis and characterization of a dye-functionalized polythiophene with different chromic properties

As a preliminary study aiming to possible applications, a polythiophene derivative with an azobenzene moiety (polyazothiophene) was synthesized and characterized by FTIR, 1H NMR, DSC and HPSEC. Some aspects on the thermo- and solvatochromic properties of polyazothiophene, such as the influence of different solvents and solution concentration on the thermochromic effect, and the use of a large polarity range of solvents as well as an acid media in the solvatochromic effect were explored. Reversible thermochromic properties of dimethylformamide and toluene solutions were analyzed in the temperature range of 10–70 °C showing a blue-shift spectrum variation with temperature increase. Solvatochromic properties were observed for pure solvents and THF/hexane mixtures. Another chromic effect was achieved upon the addition of a protonic acid to the azothiophene polymer solution as result of the side- and main-chain protonation.