Fast RAFT aqueous polymerization in a continuous tubular reactor: consecutive synthesis of a double hydrophilic block copolymer

In this work, double hydrophilic diblock copolymer poly(3-sulfopropyl methacrylate potassium salt)-b-poly(poly(ethylene glycol) methyl ether methacrylate) (PSPMA-b-PPEGMA) was successfully synthesized via a fast reversible addition–fragmentation chain transfer (RAFT) polymerization at 70 °C in a continuous tubular reactor in water without handling the intermediate macro-RAFT agent. An extremely high conversion was reached in a relatively short time (less than 2 h). 4-Cyano-4-(thiobenzoylthio)pentanoic acid (CTBCOOH) was used as the chain transfer agent and 2,2′-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (AIBI) was used as the initiator. Typical “living”/controlled characteristics of the polymerization system were demonstrated: first-order polymerization kinetics, a linear increase in the molecular weight with monomer conversion, and a narrow molecular weight distribution for the resultant polymer. 1H NMR spectroscopy and chain-extension experiments confirmed the attachment and “livingness” of the RAFT terminal group in the obtained polymer chain ends.