Phenol-, 2-naphthol-, and 1-nitroso-2-naphthol-blocked toluene diisocyanate (TDI) and isophorone diisocyanate (IPDI) adducts and their polymers with PPG-1000 were prepared and characterized by nitrogen estimation, IR, and H-1-NMR spectroscopy. The absence of an IR absorption band at 2270 cm-1 confirmed the completion of the reaction between the isocyanate and the blocking agents, whereas the presence of a band at 1075-1150 cm-1 confirmed the formation of poly (ether urethanes). The deblocking temperatures were determined by the use of DSC and by the carbon dioxide evolution methods. The thermal stabilities of the 2-naphthol-blocked diisocyanates were less than the phenol-blocked diisocyanates. Dissociation temperature was also reduced by the nitroso group in the blocking agent. Mass spectral data confirmed the product analysis. The solubility of the adducts were determined in the different polyols. Adducts based on IPDI showed better solubility than did those based on TDI.