Engineering pH-Responsive High Internal Phase Pickering Emulsions Stabilized by Copolymer Nanoparticle-Lipase...

Enzymatic microreactors with sustainable operational stability have attracted significant interest in the development of green synthesis. In this work, a recyclable and pH-responsive enzymatic microreactor was constructed on the basis of high internal phase Pickering emulsions (HIPPEs). Oil-in-water HIPPEs were prepared via simple hand-shaking emulsification adopting amine-functionalized diblock copolymer nanoparticle/lipase complexes as Pickering emulsifiers. The amine-functionalized nanoparticles, composed of poly(oligo(ethylene glycol) methyl ether methacrylate)-b-poly(diacetone acrylamide), were synthesized through the combination of RAFT-mediated polymerization-induced self-assembly and subsequent hydrolysis. The obtained HIPPEs displayed reversible emulsification/demulsification behaviors triggered by protonation/deprotonation of amine groups on the surfaces of nanoparticles. When applied to the esterification of butyric acid with 1-butanol, the as-prepared HIPPE-based microreactor exhibited outstanding catalytic efficiency due to the large interfacial area and shortened diffusion distance provided by the high-internal-phase structure. Moreover, pH-triggered demulsification enabled convenient product separation and efficient recycling of the nanoparticle/lipase complexes for repeated catalytic runs, demonstrating good sustainability and promising potential for practical applications.