Ultrasonication enhanced photocatalytic solvent-free reversible deactivation radical polymerization up to high conversion with good control

Focusing on energy-saving and environmentally-friendly polymerization engineering, ultrasonication and light were employed as coupled physical stimuli to regulate solvent-free reversible addition fragmentation chain transfer polymerization (RAFT), atom transfer radical polymerization (ATRP) and iodine transfer polymerization (ITP). The solvent-free polymerizations of (meth)acrylate under different conditions were performed with good control even at high monomer conversion (>90%), yielding polymers with low values of dispersity and retention of chain-end functionality. Kinetic experiments and mechanistic insights confirmed that light triggered different photocatalytic pathways (e.g. oxidative quenching cycle for RAFT, reductive quenching cycle for ATRP, photogenerated radical species for ITP) to initiate and mediate the solvent-free polymerizations and ultrasonication was used as an effective process intensification method to improve the diffusive of photocatalysts and their derivatives to alleviate the diffusional limitations for keeping good control up to high monomer conversion. This as-developed strategy is proved to be an efficient technology to produce well-defined polymers without complicated processes of products separation from solvent and residual monomer removal.