Revealing triple-shape memory effect by polymer bilayers.

Bilayer polymers that consist of two epoxy dual-shape memory polymers of well-separated glass transition temperatures have been synthesized. These bilayer epoxy samples exhibit a triple-shape memory effect (TSME) with shape fixities tailorable by changing the ratio between the two layers. The triple-shape fixities of the bilayer epoxy polymers can be explained by the balance of stress between the two layers. Based on this work, it is believed that the following three molecular design criterions should be considered in designing triple-shape memory polymers with optimum TSME: 1) well-separated thermal transitions, 2) a strong interface, and 3) an appropriate balance of moduli and relative ratios between the layers (or microphases).