Isothermal programming of triple shape memory

Here we present a new strategy for enabling triple shape memory (TSM), in which different shapes may be programmed at one constant fixation temperature during isothermal crystallization of a poly(octylene adipate) elastomer. Unlike traditional TSM programming techniques that utilize separate thermal transitions to encode each distinct shape, here we report that multiple shapes may be encoded independently at different time stages of the same isothermal crystallization process, and then recovered sequentially at different temperatures upon heating. As such, the new method extends TSM capabilities to conventional semicrystalline elastomers that exhibit a single and narrow thermal transition. Unexpectedly, shape fixation does not depend on crystallinity acquired prior to sample deformation, which suggests that different shapes are secured by an individual crystalline scaffold with minor contribution of the pre-existing crystals. To that end, the isothermal protocol for TSM programming was utilized to demonstrate a one-way reversible shape memory transformation controlled by fixation time. (C) 2015 Elsevier Ltd. All rights reserved.