Hydroxylated poly(styrene-b-butadiene-b-styrene) triblock copolymer (HO-SBS), with crosslinked networks, was prepared using various amounts of toluene diisocyanate (TDI). The amount of TDI was 0, 0.5, 1, 2, and 5 wt %. The effects of different contents of TDI on the microstructure, thermal properties, and mechanical properties of the crosslinked networks were investigated in detail. Fourier transform infrared spectra indicates that the reaction between -OH and -N=C=O have take place, and the solid-state nuclear magnetic resonance spectra confirms that the crosslinked structure has been obtained. The results of scanning electron microscopy show that the mode of fracture surfaces transmits gradually from tough fracture to brittle fracture, but the structure of microphase separation is still observed at the same time. Mechanical test indicates that crosslinking is a useful method to regulate mechanical properties of the HO-SBS. The results of dynamic mechanical thermal analysis display that there are two glass transition temperatures, which also means that the microphase separation is still in existence. Moreover, the glass transition temperature of the polybutadiene domains shifts to higher temperature. Accordingly, the microstructure, glass transition temperature, solvent resistance, and mechanical properties of the HO-SBS are influenced obviously by the crosslinking of TDI. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 1162-1169, 2011