A simple and effective synthetic route to cyclic polymers has been developed based on the rotaxane chemistry: (i) selective cyclization of two self-complementary sec-ammonium-containing crown ether monomers to afford [c2] daisy-chain bifunctional initiators, (ii) living polymerization to afford the corresponding linear polymers, and (iii) a rotaxane-based topological transformation of these linear polymers to furnish cyclic polymers. The key step in this sequence is the quantitative cyclization via self- assembly of two crown ether molecules with hydroxyl and sec-ammonium moieties. After the living polymerization, the linear polymers release the daisy-chain assembly to generate a cyclic topology. The specific advantages of the present synthetic protocol, i.e., procedural simplicity and concentration independence, are demonstrated by a gram-scale synthesis.<br/>As an application of present method, a reversible linear-cyclic topological transformation of a polymer chains facilitated by a long-range rotaxane switch will be reported.

A rational entry to cyclic polymers via rotaxane-based topological transformation

ACS Spring 2022

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