Ultrafast Polymerization within Crowded Droplets: A Platform Based on Macromolecular Crowding and Complex Coacervation

Biomolecular condensates are coacervates formed by liquid–liquid phase separation and organized for autocatalytic biochemistry. Nevertheless, coacervate autocatalysis remains largely unexplored. Herein, we present a model droplet system to provide fresh insights into the coacervate autocatalysis. The model droplet system was established via macromolecular crowding and complex coacervation of a water-soluble apolar polymer with amino acid-based charged monomer clusters within the simple coacervates. The macromolecular crowding and complex coacervation facilitate monomer accumulation/activation (one polymer: dual roles) leading to the autocatalytic ultrafast photoinitiated reversible addition–fragmentation chain transfer (RAFT) polymerization, faster than reported ultrafast photoiniferter polymerization-induced self-assembly despite the intrinsic retardation by RAFT than by the iniferter. This autocatalysis is validated by (i) using a nonionic monomer to provide less polar microenvironments to promote coacervate desiccation, coalescence, and liquid-to-solid transition, leading to the fairly small reaction rate enhancements; (ii) using an ionized monomer to promote droplet swelling and compartmentalization, leading to the unprecedented reaction efficiency (100% conversions within 60 seconds). Sequence-encoded changes in microenvironments can feedback to reaction rates. These findings provided fresh insights into coacervate autocatalysis potential for nanoreactors.