Polymer Chemistry Methods to oxidize carbonhydrogen (C–H) bonds under mild conditions are showing increasing promise in streamlining small-molecule synthesis. Chen et al. report an application tailored instead to a macromolecule: polyethylene. The world's most common plastic has proven hard to tweak without damaging its structural integrity, but a ruthenium porphyrin catalyst is just selective enough to introduce hydroxyl and carbonyl substituents without disrupting the backbone. The oxidized polymers remained mechanically robust while showing improved adhesion properties and wettability by simple latex paint. Chem 7 , P137 (2021).