The shape-memory effect in ionic elastomers: fixation through ionic interactions

摘要

Shape-memory elastomers based on a commercial rubber cross-linked by both ionic and covalentudbonds have been developed. The elastomeric matrix was a carboxylated nitrile rubber (XNBR) vulcanizedudwith magnesium oxide (MgO) providing ionic interactions that form hierarchical structures. The so-namedudionic transition is used as the unique thermal transition responsible for the shape-memory effect (SME)udin these elastomers. These ionic interactions fix the temporary shape due to their behavior as dynamicudcross-links with temperature changes. Covalent cross-links were incorporated with the addition of differentudproportions of dicumyl peroxide (DCP) to the ionic elastomer to establish and recover the permanentudshape. In this article, the SME was modulated by modifying the degree of covalent cross-linking, whileudkeeping the ionic contribution constant. In addition, different programming parameters, such as deformationudtemperature, heating/cooling rate, loading/unloading rate and percentage of tensile strain, were evaluatedudfor their effects on shape-memory behavior.