Design rules for performing water-sensitive ring-opening polymerizations in an aqueous dispersion

The water sensitivity of ring-opening polymerizations (ROP) prevents any polymerization technique using water as a solvent which ultimately sets a limit on the polymeric material accessible. We implement a droplet microfluidic encapsulation strategy to create polyester and polyether particles dispersed in water. In this work, we systematically investigated the process and formulation parameters that govern the stability of the micro-droplets during generation, flow, and collection. More specifically, we tune droplet viscosity, surface tension, and hydrophobicity through the addition of amphiphilic block copolymers (ABC) and hydrophobes to further shield the ROP catalyst in the aqueous dispersion. The increased catalyst stability ultimately results in higher monomer conversion and higher molecular weight polymer. We subsequently show that by changing the ABC composition, we can further tune the ROP reaction time. Finally, we applied the encapsulation technique and formulation optimization to perform another water-sensitive ROP in an aqueous dispersion. Utilizing our design rules to tune the viscosity and surface tension of the droplets, we successfully synthesized polyether particles dispersed in water. Overall, we demonstrate the power and versatility of the encapsulation methodology and establish the fundamental guiding principles to encapsulate water-sensitive polymerization catalysts to yield spherical polymer particles dispersed in water.