Renewable Phenolic Resins Based on Nitrogen-Coordinated Cyclic Boronic Ester Bonds

Abstract

Phenolic resins (PRs) are known for their exceptional performance due to their 3D cross-linked structure formed during curing. However, this crosslinking makes them non-reprocessable and difficult to recycle, leading to significant environmental pollution and resource waste. In this study, the reactivity of the phenolic hydroxyl group in thermoplastic PR (abbreviated as NR) is utilized to introduce a highly stable nitrogen-coordinated cyclic boronic ester (NCB) group into traditional carbon-chain polymers with the aid of aliphatic isocyanates. This dynamic cross-linked polymer, based on NCB linkages, not only deforms conveniently under appropriate stimuli but also retains excellent dimensional stability and mechanical properties in service environments. This approach gives full play to the good processability and mechanical performance of NR, enabling the closed-loop recycling of waste phenolic resins. This method provides a promising solution for sustainable and efficient recycling, offering a novel pathway to reduce the environmental impact of phenolic resins.