Electrochemical Postfunctionalization of Polymers: Versatile Strategies for Macromolecular Transformation

Postsynthetic modification of polymers is a crucial strategy for tailoring macromolecular properties and achieving complex architectures that are typically inaccessible through the polymerization of available monomers alone. However, conventional chemical editing typically relies on stoichiometric amounts of hazardous oxidants or reductants, extreme temperatures, and heavy metal catalysts, presenting significant environmental and economic challenges. In recent years, the electrochemical transformation approach has emerged as a powerful, mild, and highly sustainable alternative. Because electrons serve as the sole redox reagent, electrochemical postfunctionalization operates under ambient conditions without generating stoichiometric waste, inherently aligning with the principles of green chemistry. This approach not only eliminates toxic reagents but also provides simple reaction protocols and enables precise control over the degree of functionalization by tuning the applied potential or current, thereby enabling systematic tailoring of macromolecular properties. This review categorizes electrochemical postfunctionalization into four distinct mechanistic modes. The first mode involves direct activation of polymer films deposited on electrodes, where heterogeneous electron transfer initiates modifications. The second mode involves direct activation of dissolved polymers, enabling homogeneous transformations along the macromolecular chain. The third mode employs redox-mediated indirect activation, overcoming kinetic barriers and facilitating polymer backbone modification. Finally, the fourth mode involves electrochemically generated reactive species that migrate from the electrode to react with polymers in solution. Based on these fundamental modes, we highlight the electrochemical postfunctionalization of conjugated polymers. A critical factor governing these transformations is the solubility of the oxidized (doped) polymer species, which determines whether the reaction proceeds in the solid state or in solution. Careful selection of appropriate reaction conditions enables highly efficient modifications, allowing precise tuning of the optical, structural, and electronic properties of the resulting polymers. These advances enable the development of next-generation organic electronic materials. Furthermore, this review explores the application of electrochemical postfunctionalization to nonconjugated commodity plastics, including polystyrene, poly(vinyl chloride), and poly(vinylidene chloride), to address the global waste crisis. For these chemically inert materials, solution-phase electrochemical activation provides efficient and sustainable upcycling pathways. These strategies enable simultaneous deconstruction of persistent plastic waste and generation of value-added fine chemicals, thereby transitioning waste management toward chemical valorization. This review demonstrates that electrochemical postfunctionalization provides a unified and sustainable platform for polymer modification, advancing both the development of functional materials and the realization of a circular plastics economy.