Polyurethane elastomers pendant with ate-dye were prepared by N-substitution by a two-step process. First, the polymer is metalated by sodium hydride, and then the prepared urethane polyanion is treated with omega-bromohexyloxyphenyl-p-nitroazobenzene. The polyurethanes were characterized by NMR, UV, FTIR, GPC, DMA, X-ray, and polarized optical microscopy. The reaction caused cleavage of some allophanate bond degradation and narrower MW distribution. As the substitution degree increased, the hydrogen bonds in polyurethane diminished and phase mixing with ate-dye was enhanced. Photoisomerization of the pendant ate-dye was also observed.