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 T(prog) and the applied strain epsilon(m) 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 R(r) and the switching temperature T(sw), while the maximum recovery stress sigma(max) was determined at the characteristic temperature T(sigma,max) under constant strain conditions. Excellent shape-memory properties were achieved in all experiments with R(r) values in between 80 and 98%. sigma(max) could be tailored from 0.4 to 3.7 MPa. T(sw) and T(sigma,max) could be systematically adjusted from 33 to 71 degrees C by variation of T(prog) 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.