Polyurethane Cationomers with Azobenzene Side Groups in the Flexible Component. Synthesis, Characterization, and Properties

Azo poly(tetramethylene oxide) diols containing one azobenzene side unit on the chain are proposed as intermediates for chromophoric polyurethanes, to avoid difficulties linked with the photochromic behavior of some azo polyurethane cationomers in the film state. Starting from the azo diols of different molecular weight, 4,4’-dibenzyldiisocyanate and N-methyldiethanolamine, followed by a quaternization with chloroacetamide, two polyurethane cationomers with azobenzene in the soft segment were synthesized and characterized. As a reference polymer, the azo non-ionomeric polyurethanes were also synthesized and characterized. Indeed, it evidenced that under UV irradiation, the polymeric films exhibited photochromic behavior, explained by the molecular mobility of the azo chromophore inserted in the polyether component but controlled of the electrostatic interactions between neighboring chains, specifically to the ionomeric matrix. These polymers are known for their elastomeric nature and is assumed to be of interest in some future applications.