Segmented poly(ether urethanes) with anthracene built into the hard segment based on 4,4'-diphenylmethylene diisocyanate or hexamethylene diisocyante, 1,4-butanediol, 2,6-(dihydroxymethyl)anthracene, and poly(oxytetramethylene) soft segments were synthesized. The photo-induced cycloaddition of anthracene in these polyurethanes has been studied by UV-Vis spectroscopy. A reversible change of the refractive index of polymer films could be achieved.