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Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers
Published on: December 16, 2022
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Cleavable Comonomers for Chemically Recyclable Polystyrene: A General Approach to Vinyl Polymer Circularity
Gavin R Kiel1, David J Lundberg2, Elisabeth Prince1
1Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
Journal of the American Chemical Society
|June 28, 2022
Summary
New thionolactone additives enable chemical recycling of vinyl polymers like polystyrene. This process allows for depolymerization and repolymerization, creating recyclable plastics with similar properties to the original material.
Area of Science:
- Polymer Chemistry
- Materials Science
- Sustainable Chemistry
Background:
- Vinyl polymers, such as polystyrene, are prevalent but pose recycling challenges due to their environmental persistence.
- Current recycling methods often result in degraded material properties, limiting true circularity.
- Incorporating cleavable units into polymer backbones offers a potential route to enhanced recyclability.
Purpose of the Study:
- To develop and evaluate thionolactones as cleavable comonomer additives for vinyl polymerization.
- To demonstrate the chemical deconstruction and recycling of vinyl polymers using these additives.
- To investigate the properties and recyclability of the resulting polymers.
Main Methods:
- Free radical polymerization incorporating thionolactone comonomers into polystyrene (PS) and other vinyl polymers.
- Selective chemical depolymerization of the modified polymers.
- Oxidative repolymerization of the depolymerized fragments.
- Characterization of polymer molar mass, properties, and recycling efficiency.
Main Results:
- Statistically incorporated thioester linkages (2.5–55 mol %) enabled selective depolymerization of PS to thiol-terminated fragments (<10 kDa).
- Recycled PS, generated via oxidative repolymerization, achieved high yields (80–95%) and near-identical molar mass to the parent material, demonstrating a molar mass memory effect.
- Deconstructable PS with 2.5 mol % linkages and its recycled counterpart exhibited thermomechanical properties comparable to virgin PS.
- The approach proved effective for a cross-linked styrenic copolymer and a polyacrylate.
Conclusions:
- Thionolactones serve as effective cleavable comonomer additives for the chemical deconstruction and recycling of vinyl polymers.
- This method facilitates the creation of recyclable polymers with retained properties, offering a general strategy for enhancing polymer circularity.
- The demonstrated molar mass memory effect and property retention suggest a viable pathway toward sustainable polymer management.
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