Tacticity Engineering: Decoupling Bond-Formation from Stereochemical Control in the Design of Poly(Vinyl Ethers)

Tacticity in synthetic polymers governs local chain conformations and intermolecular packing, thereby exerting itself as a primary determinant of emergent material properties. However, despite its transcending effects, tacticity is generally treated as an immutable synthetic outcome rather than a variable that can be independently designed and manipulated. To isolate tacticity as a fundamentally tunable macromolecular variable, we have developed a tacticity engineering platform that decouples chain growth from stereochemical control in the design and synthesis of poly(vinyl ethers). This platform leverages photocatalytic post-synthetic hydrogen atom abstraction and transfer to controllably manipulate tacticity in pre-formed polymer scaffolds without altering other defining material characteristics, such as molecular weight, dispersity, or cross-linking density. Leveraging the photocontrol of our approach, we show that precise tacticity levels can be reliably accessed by controlling irradiation duration. We highlight that this synthetic method can be broadly applied to a library of differentially substituted poly(vinyl ethers). To showcase the utility of our tacticity engineering platform, we systematically manipulated emergent macromolecular properties and established structure-property relationships correlating tacticity to thermomechanical behavior. Rheological characterization of poly(vinyl ethers) links local packing density to the zero-shear viscosity, revealing that viscosity increases by six orders of magnitude as stereoregularity decreases. Collectively, these findings establish post-polymerization tacticity engineering as a general strategy for decoupling bond formation from stereochemical programming in synthetic matter, while forging a direct link between tacticity and viscoelastic properties and indicating its promise for designing next-generation functional materials.