A rational entry to cyclic polymers via spontaneous and selective cyclization reactions

Abstract

This focus review describes the status quo of synthetic routes to cyclic compounds and cyclic polymers via spontaneous cyclization processes using (1) rotaxane chemistry and (2) dynamic covalent chemistry. Systems with rotaxane-based structures undergo spontaneous and selective cyclization of two self-complementary molecules and a macromolecular rotaxane switch, where the relative position of each component can be controlled, which results in a topology change from linear to cyclic. Systems based on dynamic covalent chemistry use exchange reactions of bis(2,2,6,6-tetramethylpiperidin-1-yl)disulfide (BiTEMPS) units that behave as stable linkages at r.t. and exchange disulfide bonds upon heating. Controlling the dynamic nature of BiTEMPS-based low-molecular-weight compounds and polymers thus provides cyclic topologies via spontaneous and selective cyclization processes. This focus review describes the synthetic routes to cyclic compounds and cyclic polymers via spontaneously occurring cyclization processes using (1) rotaxane chemistry and (2) dynamic covalent chemistry. Systems with rotaxane-based structures proceed via the spontaneous and selective cyclization of two self-complementary molecules and a macromolecular rotaxane switch, which results in a topology change from linear to cyclic. Systems based on dynamic covalent chemistry use exchange reactions of bis(2,2,6,6-tetramethylpiperidin-1-yl)disulfide (BiTEMPS) units. Controlling the dynamic nature of BiTEMPS-based molecules provides cyclic topologies via spontaneously and selectively occurring cyclization processes.