# Site-Specific Recruitment, Localization of Ionized Monomer to Macromolecular Crowded Droplet Compartments Can Lead to Catalytic Coacervates for Photo-RAFT in Dilution

## TL;DR

Researchers developed catalytic droplets that mimic biological systems by using macromolecular crowding to enable efficient reactions in dilute conditions.

## Contribution

A new method for site-specific monomer recruitment in catalytic coacervates using macromolecular crowding and confinement.

## Key findings

- Macromolecular crowding enables 97% monomer conversion in dilute conditions within 12 minutes.
- Salt-bridging molecular recognition localizes monomers to dense-phase compartments.
- Hierarchical complexation leads to compartmentalized droplets with distinct phases.

## Abstract

Catalytic coacervates, or droplet reactors, represent a forefront research area in chemistry and materials science. Despite advancements in this field, challenges persist in achieving liquid–liquid phase separation (LLPS) droplet compartmentalization and site-specific reactant recruitment/localization for reaction catalysis, similar to those within biological systems. Herein, we describe the catalytic coacervates for aqueous photo-RAFT in dilution, focusing on the site-specific recruitment/localization of ionized monomer with the aid of macromolecular crowding and confinement. Cooperative hydrogen-bonded interpolymer complexation (IPC) of imidazolium-copolymers initiates the ion-cluster formation. Further hierarchical inter-cluster complexation (ICC) leads to the LLPS droplet compartmentalization into charged dense-phase and neutral dilute-phase compartments. Site-specific recruitment and localization of the oppositely charged monomer into dense-phase compartments are achieved by salt-bridging molecular recognition. “Substantial DMA-dilution” (that is, macromolecular crowding) results in sustainable dense-phase catalytic sites within dilute-phase crowding surroundings, enabling reaction catalysis in dilution (<2% w/w monomer) to 97% conversion in 12 min. These findings underscore the key roles of macromolecular crowding and confinement in the tailorable LLPS droplet compartmentalization and also the site-specific reactant recruitment/localization essential for enzyme reaction catalysis, and provide practical guidelines for creating catalytic coacervates towards lifelike reaction functions.