Reversible Cyclic-Linear Topological Transformation using a Long-Range Rotaxane Switch

A reversible cyclic-linear topological transformation of a poly(e-caprolactone) facilitated by a long-range rotaxane switch is reported. A linear polymer, whose topology is fixed by a protonated tert-amine/crown ether interaction at the center of the polymer chain, was reversibly transformed into a cyclic polymer fixed by urethane linkage/crown ether interaction at the polymer end upon neutralization/acidification of the tert-amine moiety.