Poly(siloxane-urethane) crosslinked structures were prepared from isophorone diisocyanate, alpha,infinity-bis(hydroxybutyl)-oligodimethylsiloxane and a new hybrid diol containing hydrolysable Si-OC2H5 groups besides OH groups. The latest was synthesized by the acid-catalyzed reaction between 1,3-bis(3-glycidoxypropyl)tetramethyldisiloxane and 3-aminopropyltriethoxysilane. The formations of the urethane groups along the polymer backbone as well as the formation of the silica domains were first confirmed by the presence of the specific bands in Fourier transform infrared spectra. The resulted materials were characterized using differential scanning calorimetry, thermogravimetric analysis and scanning electron microscopy. The results of the dynamic mechanical analysis (DMA) performed at various frequencies revealed shape memory capabilities for some of the obtained structures. The silica formed because of the hydrolysis-condensation reactions proved to have reinforcing effect upon siloxane-urethane structure also evidenced by DMA and increasing water vapor sorption capacity as was measured by dynamic vapor sorption. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 1708-1718, 2011