Ferromagnetism in Metal-Free Polymers

It has recently been shown that room temperature ferromagnetism (RT-FM) can be induced in Teflon by simple stretching or cutting. The question was raised whether this is a common phenomenon in any polymer. We carried out several experiments to show that RT-FM could not be induced in all polymers. We mechanically deformed several polymers, i.e., Teflon (polytetrafluoroethylene), natural rubber (polyisoprene), PVDF (polyvinylidene fluoride), PP (polypropylene), and Parafilm (polyethylene), by simply stretching or cutting. Only Teflon and Parafilm exhibited induced RT-FM, whereas other polymers showed paramagnetic behavior. It has been believed that induced RT-FM is caused by a combination of the formation of carbon dangling bonds and ferromagnetic coupling between them. Carbon dangling bonds were generated in all polymers subjected to mechanical deformation. However, ferromagnetic coupling of the carbon dangling bonds could occur only in crystalline polymers with the right chain separation distance (5 ), e.g., Teflon and Parafilm. In addition, magnetic anisotropy could be observed in the cut Teflon and Parafilm. In both cases, the easy axis was in the direction perpendicular to the cut edges.