Synthesis and characterization of polyurethane-based shape-memory polymers for tailored T_g around body temperature for medical applications

Various polyurethane-based SMPUs were synthesized using five types of polyols as soft segments and two different diisocyanates as hard segments. The effects of diisocyanate concentration on material properties such as crystallinity, transition temperature, shape-memory effect and tensile strength were investigated. SMPUs with a maximum strain near 1000%, recovery rate up to â98%, fixity up to â90% and T_gs of 35-45°C were obtained. A high MDI content results in SMPUs with better shape-memory effect, whereas increasing IPDI content leads to a weaker shape-memory effect. High IPDI concentration seems to prevent or restrict chemical reactions and crosslinks between the polyols and the hard segments, leading to large phase separation and coexistence of soft and hard segments in the macrophases. The properties of polyurethane-based SMPUs are studied systematically using five types of soft segment polyols and two different diisocyanate hard segments. By varying the concentration of the diisocyanates and the ratio of MDI to IPDI, it was found that crystallinity, transition temperature, shape-memory effect, and tensile strength can be tailored. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.