Facile Fabrication of a Shape Memory Polymer by Swelling Cross-Linked Natural Rubber with Stearic Acid

A facile method was developed for fabrication of a robust shape memory polymer by swelling cross-linked natural rubber with stearic acid. Commercial rubber bands were swollen in molten stearic acid at 75 °C (35 wt % stearic acid loading). When cooled the crystallization of the stearic acid formed a percolated network of crystalline platelets. The microscopic crystals and the cross-linked rubber produce a temporary network and a permanent network, respectively. These two networks allow thermal shape memory cycling with deformation and recovery above the melting point of stearic acid and fixation below that point. Under manual, strain-controlled, tensile deformation the shape memory rubber bands exhibited fixity and recovery of 100% ± 10%

Shape-Memory PVDF Exhibiting Switchable Piezoelectricity

In this study, a material is designed which combines the properties of shape-memory and electroactive polymers. This is achieved by covalent cross-linking of polyvinylidene fl uoride. The resulting polymer network exhibits excellent shape-memory properties with a storable strain of 200%, and fi xity as well as recovery values of 100%. Programming upon rolling induces the transformation from the nonelectroactive α-phase to the piezoelectric β-phase. The highest β-phase content is found to be 83% for a programming strain of 200% affording a d 33 value of −30 pm V −1 . This is in good accordance with literature known values for piezoelectric properties. Thermal triggering this material does not only result in a shape change but also renders the material nonelectroactive