Sequence Distribution Control in Polyacrylate Upcycling via (Thio)urea-Catalyzed Transesterification

The sequence of repeating units along a polymer chain is a fundamental structural parameter governing macromolecular properties. However, sequence control remains a significant challenge in post-polymerization modification (PPM)-based upcycling, where functionalization typically proceeds statistically, yielding random distributions of functional groups. We present an interaction-driven strategy to regulate sequence distribution in PPM through (thio)urea-catalyzed transesterification of poly(methyl acrylate) (PMA). By systematically varying the electronic and steric substituents on (thio)urea organocatalysts, we tune the hydrogen-bonding interactions between the catalyst and the ester groups of PMA, modulating local reactivity along the polymer backbone. This approach enables control over the extent and spatial distribution of transesterification during partial upcycling to poly(methyl acrylate-co-benzyl acrylate) [P(MA-co-BnA)]. To characterize the resulting sequence distributions, we employ ¹H NMR spectroscopy combined with principal component analysis (PCA). A reference copolymer series spanning varying compositions establishes the spectral space defined by composition and sequence. PCA scores of PPM-derived copolymers are systematically displaced from this reference trajectory, reflecting sequence distributions that systematically vary with catalyst structure. These results demonstrate that catalyst–polymer interaction strength serves as a tunable design parameter for sequence regulation in PPM, offering a new handle for precision polymer upcycling.