The in situ formation of nanoparticles via RAFT polymerization-induced self-assembly in a continuous tubular reactor

In this work, the amphiphilic poly(poly(ethylene glycol)methyl ether methacrylate)-b-poly(methyl methacrylate) (PPEGMA-b-PMMA) block copolymer nanoparticles were successfully synthesized via polymerization-induced self-assembly (PISA) at 70 °C in a continuous tubular reactor (TR) with a mixed solvent of water and ethanol, using 4-cyano-4-(thiobenzoylthio)pentanoic acid (CPADB) as the chain transfer agent and 2,2′-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (AIBI) as the initiator. It was found that the addition of a high amount of water (56% v/v) hindered the transition of the copolymer morphology with only spheres being obtained. In addition, different mixers were used to investigate the effect of the mixing intensity on the evolution of the copolymer morphology with the increasing degree of polymerization (DP) of the resultant PMMA. When a T-joint was used to make PPEGMA macro-CTA (synthesized in the first stage tube) and MMA join together and flow into the second stage tube, an approximately constant particle diameter was observed during the polymerization process. In contrast, the use of a static mixer resulted in kinetically-trapped spheres. Furthermore, the particle diameter gradually increased with the increasing target DP of the PMMA, which was controlled by varying the concentration of the PPEGMA macro-CTA solution.