A series of polyurethaneurea (PUU) aqueous dispersions were synthesized from castor oil and difunctional poly (oxypropylene) polyol(GE-210

Mn=1000)

and the effect of castor oil／GE-210 composition on the morphologies and mechanical properties for these different PUU films was studied．The experimental results show that there was some compatibility between the hard segments and soft segments for the PUU based on GE一210

and the high degree of hydrogen-bonded urea carbonyl groups and the perfect ordered structure of hard segments observed for this kind of PUU resulted in higher tensile strength and elongation at break but lower elastic module and hardness of the film．For the PUU synthesized from castor oil

the degree of hydrogen-bonded urea carbonyl groups and the ordered structure of hard segments were suppressed by chemical crosslinking existing in the system

giving lower tensile strength and elongation at break but higher elastic module and hardness of the film．Furthermore

it is of interest to find that there were excellent comprehensive mechanical properties for the PUU films prepared with mixed polyols of castor oil and GE-210 in the composition range of around 50/50(wt/wt)

which can be correlated with their structures and morphologies．