Micron-sized aqueous droplets serve as a unique reactor that causes various chemical reactions not seen in bulk solutions, but their application in synthesizing high molecular weight products remains unclear. This study demonstrates that compartmentalization in aqueous microdroplets enclosed by oil effectively facilitates radical polymerization even without chemical initiators (Fig. 1). The polymerization proceeds by ultrasonic emulsification in the presence of a reversible addition fragmentation chain transfer agent. Hydroxyl radicals are generated near the large interface of microdroplets and initiate the polymerization reaction, which therefore converts an interfacial energy into the synthesis of polymeric materials. In sharp contrast, none of these reactions occurs in a bulk water environment. The microdroplet-derived synthesized polymers maintain some properties of controlled radical polymerization, such as linear first-order kinetics and linear increase in polymer chain length with conversion. Encouragingly, we also observed catalyst-free synthesis of functionalized poly(α-olefin) utilizing microdroplet-mediated polymerization. Our findings indicate that microdroplet may provide a novel platform to synthesize traditionally restricted polymers such as functionalized poly(α-olefin). Furthermore, this initiator-free microdroplet-induced polymerization could also suggest green pathways for synthesizing high molecular weight products in cells confined to micrometer-sized reactors without enzymes or catalysts. Our insight into the effect of reactor size on polymerization may provide relevant implications for the emerging field of microdroplet chemistry.

Microdroplet-mediated controlled radical polymerization in aqueous media

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.