Topological effects of macrocyclic polymers: from precise synthesis to biomedical applications

Polymer chain architectures play a crucial role in the physical properties of polymers and this unique phenomenon has been recognized as the topological effects. As one of the most representative architectures, macrocyclic polymers characterized by the endless topology have received extensive attention due to their distinct physical properties as compared to the linear counterparts. To understand these differences and unravel the underlying mechanisms, there is a long pursuit to efficiently fabricate macrocyclic polymers. To date, both ring-closing and ring-expansion strategies have been developed, which drastically elevates the accessibility of macrocyclic polymers. The improved availability of macrocyclic polymers enables the further investigation of the biomedical applications and the preliminary results suggest that macrocyclic polymers outperform their linear analogs in terms of improving gene delivery efficiency, elevating blood circulation time, and enhancing colloidal stability of nanoparticles.