Searching new shape memory polymer and the associating synthesis technology are critical on the development of smart materials. In this paper, a comprehensive study on Poly(hexylene adipate) PHA being the soft segment of shape memory polyurethane (SMPU) was presented. Bulk polymerization method was employed to synthesize the SMPU with different soft segment length (SSL) and hard segment content (HSC). The influences of SSL and HSC on its morphology and thermomechanical property using DSC, DXIA, POM, and shape memory behavior were presented here. The results indicate that the thermal properties, dynamic mechanic properties, and crystal morphology of SMPU are influenced significantly by SSL and HSC. And it is found that the shape fixity increases with SSL but decreases with HSC. On the other hand, the shape recovery decreases with both SSL and HSC, and the associated recovery temperature increases either with the increasing SSL or with decreasing HSC. Lastly, it is concluded that in the PHA-based-SMPU, the lower limiting value of SSL for polyurethane having shape memory effect is 2000; their response temperature varied with SSL and HSC, changing from 41.0 to 51.9 degrees C. Stable hard segment crystal are formed at above 30% HSC sample in bulk polymerization, but shape memory behavior can also be observed when its physical crosslink point are formed in the lower HSC PRA-based-SMPU. (c) 2007 Wiley Periodicals, Inc.