Polystyrene–Br End-Group Modification via Electrolysis: Adjusting Hydrogenation vs Coupling Selectivity

Atom transfer radical polymerization (ATRP) enables the precise synthesis of polymers with well-defined architectures, controlled molecular weights, and low dispersity. However, the halogen end-groups inherent to ATRP polymers can pose challenges due to their chemical reactivity and thermal instability. To address these issues, various strategies, including chemical and photochemical methods, have been developed for chain-end modification. This study introduces an electrochemical approach to selectively reduce halogen end-groups in ATRP polymers. Using glassy carbon (GC) and silver electrodes, the reductive cleavage of C-Br in bromine-capped polystyrene was investigated. Cyclic voltammetry revealed that polystyrene-bromide undergoes electron transfer accompanied by the concerted removal of the C-Br functionality. The Ag electrode facilitated electrocatalysis with enhanced activity. Controlled-potential electrolysis demonstrated that reaction conditions, particularly the choice of proton donors, significantly influence product distribution, enabling selective hydrogenation or dimerization of polystyrene-bromide chain ends. This work advances the understanding of electrochemical strategies for tailoring polymer end-group functionality.