Adjusting shape-memory properties of amorphous polyether urethanes and radio-opaque composites thereof by variation of physical parameters during programming


Various composites have been prepared to improve the mechanical properties of shape-memory polymers (SMPs) or to incorporate new functionalities (e.g. magneto-sensitivity) in polymer matrices. In this paper, we systematically investigated the influence of the programming temperature Tprog and the applied strain εm as parameters of the shape-memory creation procedure (SMCP) on the shape-memory properties of an amorphous polyether urethane and radio-opaque composites thereof. Recovery under stress-free conditions was quantified by the shape recovery rate Rr and the switching temperature Tsw, while the maximum recovery stress σmax was determined at the characteristic temperature Tσ, max under constant strain conditions. Excellent shape-memory properties were achieved in all experiments with Rr values in between 80 and 98%. σmax could be tailored from 0.4 to 3.7 MPa. Tsw and Tσ, max could be systematically adjusted from 33 to 71 °C by variation of Tprog for each investigated sample. The investigated radio-opaque shape-memory composites will form the material basis for mechanically active scaffolds, which could serve as an intelligent substitute for the extracellular matrix to study the influence of mechanical stimulation of tissue development.
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