A novel degradable flexible polyurethane (PU) foam was prepared by varying the ratio of poly(propylene oxide) (PPO) and triarm poly(propylene oxide)-block-polylactide copolymer (PPO-b-PLA), and was compared with conventional PU foams based on toluene diisocyanate (TDI) and PPO. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) showed that introducing PLA segments were able to result in a transition from a microphase separated state to a microphase mixed state and improve the microphase mixing. The changes in structure and domain size distribution associated with this transition were found to have led to enhanced mechanical properties such as the tensile strength, the elongation at break, and the rebound resilience for the PU foams containing PLA segments. Furthermore, it was observed that the network structure was destroyed by hydrolytic degradation in alkali solution (10 wt%/vol%) at 80 degrees C for 50 h, and that as the PLA content increased, the degradation rate of PU foams enhanced. POLYM. ENG. SCI., 2013. (c) 2012 Society of Plastics Engineers