Supramolecular chirality induced by chiral solvation in achiral cyclic Azo-containing polymers: topological effects on chiral aggregation

Herein, a series of azobenzene (Azo)-containing side-chain cyclic polymers were successfully synthesized by combining atom transfer radical polymerization (ATRP) and Cu(I)-catalyzed azide/alkyne cycloaddition (CuAAc) click reaction. The aggregates of linear and cyclic Azo polymers in a dichloroethane/limonene mixed solvent were characterized by circular dichroism (CD) and UV-visible spectroscopy, demonstrating that the topological structural constraint and molecular mass of cyclic polymers have clear effects on the supramolecular chirality driven by a chiral solvent. The difference between linear and cyclic Azo aggregates in supramolecular chirality became less distinct with increasing molecular mass of Azo polymers. The chiroptical switch of cyclic Azo polymers was firstly constructed by trans-cis photoisomerization and cis-trans heating-assisted reorganization processes. These interesting findings suggest that the cyclic topology has a clear influence on the behavior of supramolecular chirality induced by chiral limonene.