Triple shape memory effect in multiple crystalline polyurethanes

Remembering more than one permanent shape is an attractive research topic for shape memory materials (SMMs). In this paper, multiple crystalline shape memory polyurethanes (SMPUs) are prepared with PCL10000 and PTMG2900 by a three-step polymerization method. DSC and WAXD results show that the obtained polyurethane contains, simultaneously and independently, two kinds of crystals. In addition, it is confirmed through DMA analysis that reversible soft phase and hard domains are formed in the PCL-PTMG based SMPU system; and two-step modulus decreases at low temperature range can be obtained in the SMPU with suitable mass proportion of PCL to PTMG, e.g., 1:7. Thus, shape memory effect (SME) can be achieved in this system. Moreover, it is found that the PTMG soft segment dominates the shape memory effect when the PCL mass is lower than that of PTMG; while the PCL soft segment dominates the SME when PCL mass is higher than that of PTMG; and a two-step programing shape recovery can be achieved when the mass proportion of PCL/PTMG reaches a balance value, e.g., 3:5.