Depolymerization of Commercial Polymethacrylates Triggered by Hydroperoxides

Area of Science:

• Polymer Chemistry
• Chemical Recycling
• Materials Science

Background:

• Chemical recycling of poly(methyl methacrylate) (PMMA) and related polymers is difficult due to their stable all-carbon backbone.
• Current depolymerization methods often require PMMA structural modification, photochemical activation, or chlorinated solvents, limiting their practical application.
• There is a need for efficient and scalable depolymerization techniques for unmodified polymethacrylates.

Purpose of the Study:

• To develop a thermally driven depolymerization method for unmodified commercial polymethacrylates.
• To utilize hydrogen-atom-transfer (HAT) initiated by simple hydroperoxides for polymer backbone cleavage.
• To assess the efficiency and scalability of this novel depolymerization approach.

Main Methods:

• Utilized tert-butyl hydroperoxide (TBHP) or cumene hydroperoxide (CHP) as radical precursors for thermal initiation.
• Applied elevated temperatures (220 °C) to generate oxygen-centered radicals that abstract hydrogen atoms from polymer chains.
• Investigated the depolymerization of poly(methyl methacrylate), poly(butyl methacrylate), poly(benzyl methacrylate), and poly(phenyl methacrylate).

Main Results:

• Achieved 70% depolymerization of PMMA at 220 °C with 10 mol % TBHP.
• Recovered 55% of intact monomer, with 15% lost to side reactions due to prolonged high-temperature exposure.
• Demonstrated successful depolymerization for various polymethacrylates and moderate tolerance to ambient oxygen.

Conclusions:

• Thermally triggered HAT depolymerization is a viable and simplified method for breaking down unmodified commercial polymethacrylates.
• This approach avoids the need for photoactivation, specialized polymer structures, or chlorinated solvents.
• The findings present a promising pathway for the sustainable chemical recycling of polymethacrylate plastics.