Polymer to polymer upcycling is an attractive complement to plastic recycling. It saves energy from depolymerizing and reforming a polymer while adding functionality. Valorizing polar poly(acrylic acid) (PAA) with fluorine would add hydrophobicity and sturdy self-cleaning properties creating unique adhesive and fluorophobic polymers. These polymers could see similar applications to other fluorocarbon polymers like nonstick pans (Teflon™) and vaulted ceilings for water sports (PCTFE). Unfortunately, traditional copolymerization of polar acrylates and fluorinated olefins is met with low success.

An alternative approach is the post-polymerization fluorination (PPF) of PAA. However, classic approaches to PPF require harsh chemicals like hydrofluoric acid and sulfur tetrafluoride. A more recent report utilizes silver nitrate to synthesize poly(acrylic acid-r-vinyl fluoride) (PAA-r-PVF). However, silver is reactive with other functional groups, complicating its application to mixed plastic waste streams.

We now report a photoredox-catalyzed decarboxylative fluorination of PAA, resulting in PAA-r-PVF. The extent of PVF incorporation ranges from 33–99 mol% simply by adjusting time of light exposure. Additionally, high molecular weight PAA (450 kD) and industrial Super-Absorbent Polymers (SAPs) undergo high levels of conversion with 20 ppm catalyst loading.

In addition to valorization of SAPs derived from disposable diaper waste, a long-term goal is to combine decarboxylative fluorination with plasma oxidation of plastic polymer waste (PPW) to produce amphiphilic copolymers. We expect these unique materials to have a wide range of applications due to the facile tunability of fluoride content, making this an attractive and valuable method for repurposing plastic waste.

Mary Watson

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