General Approach to Processing/Recycling Mixed Polymers by Vitrimerization

Globally rising environmental concerns have increased the demand for recyclable polymers and efficient recycling practices. Among the many methods, the simplest and most economical way to recycle polymers with a minimal carbon footprint is by repairing or re-melting them into new items. However, most polymers are not miscible with each other, requiring polymer waste to be sorted by type prior to recycling. This laborious sorting process substantially limits the polymer recycling rate. To address this challenge, we present a general approach to recycling mixed polymers. This can be achieved by oxidizing the polymers, followed by mixing them with boronic acid as a dynamic crosslinker. Hydroxyl groups can be formed in many commodity polymers (PE, PP, and PS) during the oxidation process, which can then form dynamic boronic ester bonds with boronic acid. The dynamic crosslinks formed between mixed polymer chains prevent phase separation, even after extensive thermal annealing. Using this approach, mixed polymers can be processed multiple times without deteriorating their mechanical properties.