# Photo-initiated solvent-mediated depolymerization of consumer poly(methyl methacrylate) without chlorinated reagents

## TL;DR

Scientists developed a low-temperature method to recycle PMMA plastic into its original monomer using UV light and non-chlorinated solvents.

## Contribution

A new low-temperature chemical recycling method for PMMA that does not require chlorinated reagents.

## Key findings

- PMMA can be efficiently depolymerized at 120-180°C using UV light in oxygen-free conditions.
- Non-chlorinated solvents like benzonitrile enable complete unzipping of PMMA without radical termination.
- Chlorine radicals are not essential for depolymerization but can functionalize PMMA for upcycling.

## Abstract

The chemical recycling of commodity acrylic polymers, such as the transparent thermoplastic polymethyl methacrylate (PMMA), typically requires temperatures of 350-400°C. Herein, we report chemical recycling back to monomers for PMMA between 120-180°C, through UV illumination under oxygen-free conditions. We have achieved gram-scale degradation of consumer plastic with >95% conversion, yielding >70% monomer, which can be readily repolymerized. The process proceeds even at high concentrations (>1 M) and depends strongly on solvent choice: aromatic solvents like dichlorobenzene and diphenyl ether maximize conversion. In contrast to a concurrently published study, we report that chlorine radicals are not required for depolymerization; however, when present, they react with the unzipping chain to form chlorine-functionalized PMMA which can be upcycled through derivatization. In more sustainable non-chlorinated solvents such as benzonitrile, minimal termination by radicals enables complete unzipping. These findings demonstrate a low-temperature, scalable route for the chemical recycling of PMMA, offering alternative pathways for plastic circularity.

Chemical recycling of poly(methyl methacrylate) (PMMA) typically requires high temperatures. Here, the authors report the UV-initiated depolymerisation of PMMA at low temperatures, in non-chlorinated solvents, such as benzonitrile.