Stimuli-degradable cross-linked polymers synthesized by radical polymerization using a size-complementary [3]rotaxane cross-linker

Stimuli-degradable cross-linked polymers were developed by applying both topological linkage and size complementarity of rotaxane to cross-link their structures. A double vinyl group-tethering [3]rotaxane cross-linker was prepared by reacting the axle ends of sec-ammonium/crown ether-type pseudo[3]rotaxane with a suitably bulky end-cap agent that was as large as the cavity of the wheel. Radical polymerization of a common vinyl monomer in the presence of the [3]rotaxane cross-linker afforded the corresponding stable cross-linked polymer under ambient conditions. An anion exchange reaction with tetra(n-butyl)ammonium chloride caused selective and efficient de-cross-linking of the cross-linked polymers to the vinyl polymer and the axle component of the cross-linker.