This article deals with the synthesis and characterization of novel polyurethanes (PUs) by the reaction between two aromatic diisocyanates (4,4'-diphenylmethane diisocyanate and tolylene 2,4-diisocyanate) and two aliphatic diisocyanates (isophorone diisocyanate and hexamethylene diisocyanate) with N-1,N-4-bis[(4-hydroxyphenyl)methylene]succinohydrazide azide, which acted as hard segment. UV-vis, FTIR, H-1 NMR, 13 C NMR, and DSC/TGA analytical technique has been used to determine the structural characterization and thermal properties of the hard segmented PUs. X-ray diffraction revealed that PUs contained semicrystalline and amorphous regions that varied depending upon the nature of the backbone structures. PUs were soluble in polar aprotic solvents. (C) 2008 Wiley Periodicals, Inc.