HRP-conjugated thermoresponsive copolymer as a nanoreactor for aqueous polymerization of phenols

Enzymatic polymerization of phenols catalyzed by horseradish peroxidase (HRP) in aqueous solution has been regarded as a green strategy for the synthesis of phenolic polymers while the indispensable employment of additives makes the separation of the phenolic polymers extremely inconvenient and the recycling of HRP also remains great challenge. Here, an HRP-conjugated thermoresponsive copolymer P(DMAA-co-AA)-b-P(NIPAM-co-nBA)-HRP was delicately constructed as a nanoreactor for the polymerization of phenols, which proceeded efficiently in water with good regioselectivity (∼85%) and yields (∼87%) above the lower critical solution temperature (LCST, 33 °C). After completion of the polymerization, the reaction mixture was cooled below the LCST and the nanoreactor disassembled to be fully water-soluble, allowing the facile separation of the insoluble phenolic polymers from the thermoresponsive catalyst. The products were isolated in nearly pure form by simple centrifugation and the supernatant containing the polymer-supported enzyme could be reused for at least 10 cycles without obvious loss in catalytic activity by the combination of the warming/cooling procedures.