Microfluidic synthesis of thermo-responsive block copolymer nano-objects via RAFT polymerization
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ORIGINAL PAPER
Microfluidic synthesis of thermo‑responsive block copolymer nano‑objects via RAFT polymerization Tomke E. Glier1 · Mohammad Vakili2,3 · Martin Trebbin2,4 Received: 16 April 2020 / Accepted: 11 September 2020 © The Polymer Society, Taipei 2020
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. Keywords Amphiphilic self-assembly · Block copolymers · Microfluidics · RAFT polymerization · Thermo-responsive polymers · Continuous flow reactor · Flow chemistry
Introduction Amphiphilic diblock copolymers consisting of a hydrophilic and a hydrophobic block are of great interest for scientific, medical and industrial applications due to their ability to form a wide range of nano-structured objects via self-assembly [1]. In an aqueous solution, for example, such amphiphilic structures can assemble into micelles composed of Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10965-020-02290-3) contains supplementary material, which is available to authorized users. * Martin Trebbin [email protected] 1
Institut für Nanostrukturforschung (INF), Center for Free Electron Laser Science (CFEL), University of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
2
Centre for Ultrafast Imaging, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
3
European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
4
Department of Chemistry, The State University of New York At Buffalo, 760 Natural Sciences Complex, Buffalo, New York 14260‑3000, USA
a hydrophobic core and a hydrophilic corona [2, 3]. While such self-assembled structures are well suitable for encapsulation and drug delivery [4–6], great control over their synthesis and composition is the key for successful and diverse applications. Polymerization-induced self-assembly (PISA) denotes a process, which is based on a chain-extension of an existing homopolymer with a second
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