Physicochemical Reaction Control Enables Molar-Mass-Selective Macromolecular Electrolysis

Abstract Tailoring molar-mass distributions postsynthetically remains a long-standing challenge in polymer chemistry that conventionally requires the synthesis of dedicated polymer libraries. Here, we show that heterogeneous macromolecular electrolysis can edit polymer-molar-mass distributions on demand from a single prepolymer sample, tuning number-average molar mass (Mn) from 60 to 902 kg mol–1 and dispersity (Đ) from 1.3 to 7. This capability arises from a previously unrecognized mode of selectivity where heterogeneous electroreduction mediates polymer substrate reactivity through physicochemical reaction control. In this electrolytic transformation, molar-mass-dependent transport physically affects the rate of redox activation with an approximately linear dependence on the diffusion coefficient of these macromolecules. This leads to preferential activation of lower-molar-mass polymers, which is a consequence of more rapidly diffusing species having preferential access to the electrode interface. Moreover, we show that during this macromolecular electrolysis, every redox-active unit on a single polymer chain is activated prior to polymer desorption from the working electrode, which is a distinct manifestation of physicochemical control. This stands in contrast to conventional postpolymerization transformations that are inherently stochastic in nature, where target units on individual polymer chains statistically react and reactions on large polymers are more likely to occur. Electrode identity controls polymer–electrode interactions. Strong radical adsorption to graphite drives complete activation of individual chains before desorption. On reticulated vitreous carbon, adsorption is weaker and reactivity reverts to stochastic activation, which causes the molar-mass distribution to shift gradually over the course of electrolysis. We leveraged these differences to arbitrarily tune molar-mass distributions postsynthetically by selectively deconstructing prototypical N-(methacryloxy)phthalimide methacrylate copolymers. These findings establish interfacial electrochemical environments as a platform for molar-mass-selective macromolecular transformations and introduce a new axis of selectivity in synthetic polymer chemistry.