Photo‐Induced Polymer Cyclization via Supramolecular Confinement of Cyanostilbenes

Efficient synthesis of cyclic polymers has received much attention in polymer chemistry field. Although photochemical cycloaddition of terminal π‐bonded units provides a plausible way toward cyclic polymerization, it remains challenging to avoid side reactions by manipulating the reaction selectivity. Herein supramolecular confinement has been developed as a promising strategy to address this issue, by introducing highly directional hydrogen bonds to the photo‐reactive cyanostilbenes. The cyanostilbenes units on both ends of a telechelic macromonomer are orientationally aligned with high local concentrations, yielding [2+2] photo‐cycloaddition products upon 430 nm light irradiation. It leads to the formation of cyclic polymers in the self‐assembled state, in stark contrast to Z‐E isomerization of cyanostilbenes in the monomeric state. Overall, supramolecular confinement effect exemplified in the current study provides new avenues toward cyclic topological polymers with high synthetic efficiency. Supramolecular confinement effect facilitates cyclic polymerization of a telechelic cyanostilbene macromonomer via [2+2] photo‐cycloaddition, in stark contrast to Z‐E photo‐isomerization in the monomeric state.