Microfluidic synthesis of thermo-responsive block copolymer nano-objects via RAFT polymerization

Abstract

Continuous flow microreactors offer advantages such as quick heat dissipation, high throughput as well as reproducible and flexible product quality. Here we present a X-ray compatible microfluidic reaction vessel suitable for studying living polymerization reactions in flow under oxygen-free conditions. Diblock copolymer nano-objects were synthesized via mixing-induced reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization in a microfluidic channel. A water-soluble macro chain transfer agent was chain-extended with N-isopropylacrylamide (NIPAm). Poly(NIPAm) is a thermo-responsive polymer with a lower critical solution temperature of 32 °C. Thus, heating the polymer solution results in the formation of micelles according to the polymerization-induced thermal self-assembly route. To implement the reaction in a microfluidic sample environment, metal-polyimide devices have been fabricated. The use of microfluidics for the synthesis of copolymers enhanced the control of reaction parameters. Moreover, the use of X-ray compatible materials paves the way for future in situ time-resolved structural studies of the flowing species.