Biopolymers materials with tunable properties are the spotlight in the polymer molecules design and synthesis. Here, we synthesize a series of castor oil based-waterborne polyurethanes (CWPUs) with highly tunable properties by adjusting the content of 2,2-dimethylolbutanoic acid (DMBA), a hydrophilic chain extender. The size of the polyurethane dispersions (PUDs) decreases from 120 nm to 20 nm, when DMBA content increases from 5 to 9 wt%. Infrared spectrum of the corresponding CWPUs films shows that the hydrogen bonds between hard segments have an enhancement as DMBA content increases. The thermal and mechanical properties of the CWPUs films have an obvious change due to this enhanced hydrogen bond interactions and behave like soft elastomer or rigid plastic. For example, the glass transition temperature (T-g) of the CWPUs films increases from 47.8 to 92.9 degrees C and meanwhile the tensile strength increases from 9.6 to 20.0 MPa. In addition, the CWPUs films are enzymatically hydrolysable due to the surface hydrophilicity. Importantly, those films exhibit excellent biocompatibility to mouse fibroblast (L-929) cells and a relative cell viability of 76% compared to tissue culture polystyrene (TCPS) plates is obtained.