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 degrees 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%.