Sono-RAFT Polymerization-Induced Self-Assembly in Aqueous Dispersion: Synthesis of LCST-type Thermosensitive Nanogels

The first sonochemically induced reversible addition–fragmentation chain transfer by the polymerization-induced self-assembly process (Sono-RAFT-PISA) has been investigated. High-frequency ultrasound (490 kHz, 40 W) was applied for the controlled polymerization of N-isopropylacrylamide (NIPAM) in aqueous dispersion via the Sono-RAFT-PISA technique using poly­(poly­(ethylene glycol) methyl ether acrylate) (PPEGA) as both macromolecular chain transfer agent and surfactant (macro-transurf). The synthesis of PPEGA-b-PNIPAM copolymers in aqueous media at 20 °C (DP_n,NIPAM = 204) was found to reach total NIPAM conversion in a short time (60 min.) with narrow molecular weight distribution (Đ < 1.26). Furthermore, PNIPAM-based spherical nanogels (D_h ≤ 69 nm, pdi ≤ 0.26) were successfully synthesized by Sono-RAFT-PISA (aqueous dispersion, 45 °C), qualifying as a highly “green” method due to the complete monomer conversion, absence of organic initiator, of residues, and to the unique use of water as initiator and solvent (inisolv).