Recyclable Polymers with Boronic Ester Dynamic Bonds Prepared by Miniemulsion Polymerization

Polymers with boronic ester dynamic covalent bonds were synthesized by nitroxide-mediated miniemulsion polymerization of isobornyl methacrylate (IBOMA), alkyl methacrylates (average aliphatic size of 13.0, C13MA), glycerol monomethacrylate (GMMA), and 4-vinylphenylboronic acid (VPBA). The miniemulsion polymerization of all monomers was enabled by the esterification reaction between GMMA and VPBA and the synthesis of (VPBA + GMMA) dimer prior to the polymerization. The formation of boronic ester dynamic covalent bonds was confirmed by rheological and mechanical measurements, indicating a higher stiffness by increasing the dimer content from 5% to 15% in the initial feed. Cross-linked polymers showed high reprocessing capability with a comparatively simple recycling process (at 80 °C for 45 min) and a high organic solvent absorbance of polymers (swelling ratio up to 153%). Furthermore, it was shown that the addition of VPBA and GMMA significantly improved the heat resistance of polymers up to 121 °C, compared to the IBOMA/C13MA copolymers (without GMMA and VPBA functional monomers).