Photocatalytic Direct Decarboxylation of Carboxylic Acids to Derivatize or Degrade Polymers

Abstract

Visible light-mediated direct decarboxylation of carboxylic acids with an acridine photocatalyst is a convenient and powerful method to generate carboncentered radicals in polymer chains. Advantageously, this process proceeds under mild conditions, without preactivation of the acid groups. We utilize decarboxylation in the presence of a hydrogen atom donor to form statistical acrylate-ethylene and acrylate-propylene copolymers, which are challenging to obtain by direct polymerization. We additionally show that decarboxylation of methacrylic acid units within polymethacrylates can trigger degradation of the polymer backbones. Moreover, a dual catalytic approach, which combines the function of an acridine photocatalyst with that of a cobaloxime catalyst, is leveraged to furnish unique copolymers with pendent alkenes. Our work indicates that direct decarboxylation is a versatile technique for the synthesis of functional materials with tailored compositions and properties.

Mild Catalytic Degradation of Crystalline Polyethylene Units in a Solid State Assisted by Carboxylic Acid Groups

“…14 In this study, the mild degradation of carboxylated PEs (PE-COOH, M n = 8000−21,000, HDPE-or LDPE-like ones) to fragments with molecular weights close to common waxes (M n ≈ 500) has been achieved by Ce-photocatalysis and dioxygen as the only stoichiometric oxidant under mild conditions in a polar solvent (even in water) (Figure 1b-ii). 15,16 In addition to the use of wax itself, such degradation would facilitate further degradation, e.g., the gasification process, for two-step chemical recycling of PE-COOH. 17,18 Contrary to the conventional oxidative degradation of polyolefins, nearly quantitative recovery of carbon atoms has been achieved with suppression of the overoxidation to CO 2 .…”