[SY-H1] Thermomechanical behavior of shape-memory polyurethane copolymer : A coarse-grained molecular dynamics simulation
Shape-memory polymers (SMPs) are smart materials that react to external stimuli to restore their original shape. The stimuli can be various things such as light, heat, humidity, and so on. Segmented polyurethane copolymer is a representative thermo-responsive SMP which are synthesized with a polyol and an isocyanate. The hard-segment which is clustered together helps to memorize the original shape by stabilizing the network, and the soft-segment which can achieve polymer crystallization acts as a switching-segment which fixes the temporary shape and induces the shape-memory effect. This dual-segment system is a necessary condition for shape-memory behavior of polyurethane. Full-atom molecular dynamics (MD) simulation can cover the atomistic structures and shape-memory properties, but it has limitations on observing mesoscale phenomena such as polymer crystallization, and micro-phase separation. To overcome this issue, we have developed a coarse-grained (CG) MD model with reduced degrees of freedom by treating multiple atoms as a single bead. Full-atom MD simulation was performed to obtain intra- and inter-bead potential of the CG model via iterative Boltzmann inversion (IBI) method. As a result, we could observe the crystallinity and shape-memory properties of SMPU models with different hard-segment contents. Then, the effect of microstructure on the mechanical deformation and shape memory behavior were investigated. We expect this study provides an insight to design the segmented polyurethane copolymer with enhanced shape recovery performance.