Synthesis of Linear and 100% Hyperbranched Polymers Through Polycondensation Based on the Friedel–Crafts Hydroxyalkylation Reaction Between an Aldehyde and Activated Phenyl Ring With Reaction‐Enhanced Reactivity of the Intermediate Mechanism

ABSTRACT Thanks to their branching structures, hyperbranched polymers have shown attractive features over linear polymers in both theoretical research and practical application fields. However, the synthesis of 100% hyperbranched polymers under mild conditions remains a challenge. In this study, the acid‐catalyzed Friedel–Crafts hydroxyalkylation type polycondensation of diphenyl ether and 4‐nitrobenzaldehyde was found to produce linear polymer readily. Because of the specific reaction‐enhanced reactivity of the intermediate mechanism of the hydroxyalkylation reaction, 4‐nitrobenzaldehyde moieties functioned as linkers to connect diphenyl ether at their 4,4′ positions in the structure of the obtained linear polymer. Based on the same mechanism, an AB2 monomer was designed, synthesized, and polymerized to obtain 100% HBP terminated with aldehyde groups. Finally, the terminal groups of HBP can be transformed into methyl groups through a similar reaction with anisole. This study provided a new strategy for the preparation and terminal functionalization of 100% hyperbranched polymers.