Synthesis and characterization of PCL¿PLLA polyurethane with shape memory behavior

Shape-memory polymers have been developed in the last years as a valid alternative to more traditional shape-memory materials with applications in several advanced sectors and with particular interest in the biomedical field. In this work, the synthesis and characterization of a stimuli responsive polyurethane, based on a synthesized tri-block PCL-PLLA copolymer, is reported. Its characteristics, in terms of physico-chemical properties as well as mechanical behavior, have been investigated and correlated with the polymer structure. The complex crystalline structure has been obtained by thermal analysis and by Small Angle X-ray Scattering (SAXS). This polyurethane is synthesized using two different molecular segments: PCL, that constitutes the soft segments; and PLLA, that constitutes the hard segments. PCL and PLLA can be considered as the switching and the fixed phase, respectively, and due to their synergetic combination, this material has shape-memory behavior. In particular, shape-memory behavior has been verified at different elongations, 50%, 100%, 200% and 350% respectively, and at a temperature close to 40 degrees C, very close to the human body temperature. So, the polyurethane synthesized can be considered as a shape-memory polymer with potential biomedical applications.