Photochromism of polyurethane cationomers with pendent azo groups

A new polyurethane cationomer with pendent azo groups bounds to quaternary nitrogen atoms has been synthesized by polyaddition reaction between poly(tetramethylene oxide) (PTMO), 4,4′-bibenzyldiisocyanate and N-methyldiethanolamine, followed by quaternization of tertiary nitrogen with 4-(3-chloropropionyloxy)azobenzene. E–Z photoisomerization of azo chromophores by UV irradiation with a high pressure mercury lamp and Z–E thermal relaxation were studied both in solution and film. An azo urethane model and a synthetic mixture of polyurethane cationomer with azobenzene were used for comparison.