Based on the typical two-step polyurethaneurea synthesis, a new series of self-crosslinkable polyurethane (PU)-urea formulations, consisting of poly(tetramethylene oxide) and 4,4'-diphenyl methane diisocyanate, and extended by ethylenediamine (EDA)/aminoethylaminopropyltrimethyoxysilane (AEAPS), were prepared. FTIR, ESCA, WAXD, DSC, and mechanical properties of samples were recorded. The results show that the self-crosslinkable polyurethane-urea could be crosslinked by hydrolysis of the trimethyloxysiloxane group to form the silsesquioxane structure. These structures represent a kind of nanosize, cagelike, chemical crosslink site as well as filler, which affect the properties of PU. The morphology, varied with different ratios of EDA/AEAPS, was also discussed. (C) 2003 Wiley Periodicals, Inc.