Chain Microstructure as a Noncovalent Catalyst: Intrachain π–π Stacking Controls Rate in Fluorinated Polyester ROCOP

The growing polymer chain is typically viewed as a passive product of catalysis, yet here we show that its microstructure can actively govern catalytic rate. In the ring-opening copolymerization (ROCOP) of fluorinated epoxides with cyclic anhydrides, rate acceleration occurs most clearly when both monomers are aromatic and only one is fluorinated. Density functional theory and mechanistic experiments rule out interactions with the catalyst as the origin of this effect, instead implicating intrachain π–π stacking between the fluorinated carboxylate chain end and aromatic units of the growing polyester as the dominant transition-state-stabilizing interaction. With each turnover, the polymer chain constructs a structured noncovalent environment around the active center, a role conceptually analogous to the binding cavity of an enzyme. This principle is accompanied by a broad fluorinated polyester library with tunable glass transition temperatures spanning below −14 to 144 °C, straightforward postpolymerization modification via para-fluoro thiol-click chemistry, and quantitative fluorine recovery as sodium fluoride upon degradation. These findings reframe chain microstructure as an underexploited handle for controlling reactivity in chain-growth polymerization.