Working mechanism for the mechanical behavior of shape memory polymer

As one of the most promising stimulus-responsive and smart polymer materials, shape memory polymer (SMP) has attracted great attention in the research field. There are three major research topics on the physics and mechanics of SMP summarized as: exchange between the SMP and the surrounding (e.g. heat, energy etc.), control of shape change (actuation approach, constructive modeling etc.) and its soft matter (thermodynamics, composite etc.). The shape memory effect (SME) in SMPs from the thermodynamic of intrinsic molecular structures, is induced (or triggered) by external stimuli, obeys Arrhenius rule and relaxation behavior. In this review, the mechanism of SMPs presented and discussed thermodynamics, entropy effect, mechanical behavior and stimulus-responsive shape recovery behavior, transition temperature, temperature memory effect, multi-field effect and multi-shape memory effect. Finally, the future work of mechanics forecasted and discussed.