Shape-memory metal alloys, which can be restored to an original or "remembered" shape after deformation, have found uses in the medical industry. Lendlein et al. have now extended shape memory to polymers--in this case, a family of oligo(e-caprolactone) dimethacrylate/n-butyl acrylate networks. The memory effect is obtained by connecting a crystallizable segment [the oligo(e-caprolactone)] that can form a temporary physical network to a component (the n-butyl acrylate) that can soften the network and improve the strain recovery. These materials possess application advantages over their metal counterparts in that they can be programmed at 70°C and can tolerate significantly larger deformations. The polymers can be tailored to specific shape transition temperatures and deformation characteristics by changing the proportions of the network components. The biocompatibility of the two components should allow these materials to find use in the biomedical sector. -- MSL
Proc. Natl. Acad. Sci. U.S.A. 98, 842 (2001).
