One-Step Process for Creating Triple-Shape Capability of AB Polymer Networks

Triple-shape polymers can move from a first shape (A) to a second shape (B) and from there to a third shape (C), where both shape changes are induced by temperature increases. This triple-shape capability is obtained for multiphase polymer networks after application of a complex thermomechanical programming process, which consists of two steps; these steps create shapes (B) and (A), while shape (C) is defined by the covalent crosslinks of the polymer network. Here, the creation of the triple-shape capability for an AB polymer network system by a simple one-step process similar to a conventional dual-shape programming process is reported. The polymer networks are based on poly(epsilon-caprolactone) (PCL) and poly(cyclohexyl methacrylate); favorable compositions for obtaining a triple shape effect have a PCL content between 35 and 60 wt%. This finding substantially facilitates handling of the triple-shape technology and is an important step toward the realization of potential applications in which more than one shape change is required.