Polyether polyurethanes: Synthesis, characterization, and thermoresponsive shape memory properties

Thermoresponsive shape memory polymers based on polyurethane with soft segment consisting of poly (tetramethylene oxide) (PTMP) and hard segment arising from urethane reaction of tolylene diisocyanate with PH terminal of PTMP and 1,4 butane diol (BD) were synthesized by a two- step process. The molar ratios of the reactants were varied to get polymers of different soft hard segment contents. These were characterized by DSC, IR, DMTA, XRD, SEM analyses, and mechanical properties. The shape memory behavior was evaluated by cyclic tensile tests. PTMO served as the switching segments whose crystalline melting was responsible for the switching behavior. As the hard segment-content increased, transition temperature (T_trans) diminished and so did the elongation and tensile strength of the polyurethane. Higher glassy/rubbery modulus ratio observed for higher hard segment-content polymer was conducive to better shape recovery properties. The influence of hard/soft segments on the thermal, mechanical, damping and shape memory properties of the copolymers are presented and correlated to their phase morphology, as investigated by FTIR and SEM.