A composition exhibiting reverse thermal gellation properties comprises a block polymer having the structure: {[An(BCB)An]}m wherein A is a polyester unit, B is a poly(ethylene oxide) unit, C is a poly(propylene oxide) unit, E is a chain extender unit, n=0-20, and m is greater than 2. The ethylene oxide:propylene oxide ratio ranges from about 0.2:1 to about 40:1. The composition has a final viscosity at a final temperature of more than twice the initial viscosity at an initial temperature wherein the final temperature is at least 10° C. higher than the initial temperature. The composition is combined with either a cellular material for tissue engineering, a cellular material for effecting repair or healing in a patient, or a bioactive agent.