Initiators for Continuous Activator Regeneration Atom Transfer Radical Polymerization of Methyl Methacrylate and Styrene with N-Heterocyclic Carbene as Ligands for Fe-Based Catalysts

Abstract

Iron-based N-heterocyclic carbene (FeX3(NHC)) complexes were used in initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP). A series of ICAR ATRPs of methyl methacrylate (MMA) and styrene (St) were carried out using FeX3(IDipp) where IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene with X = Cl (I-Cl) or Br (I-Br) and FeX3(HIDipp) (HIDipp =1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene) with X = Cl (H-Cl) or Br (H-Br). The polymerizations showed good activity, resulting in polymers with controlled molecular weights and narrow molecular weight distribution (MWD) with low loading of catalysts (50 ppm). In particular, I-Br and H-Br generated polymers with narrower MWD. For example, ICAR ATRP of MMA with 50 ppm catalysts (H-Br) after 24 h at T = 60 °C in 50% v/v anisole resulted in PMMA with Mw/Mn = 1.20 at 65% monomer conversion. ICAR ATRP of St after 72 h resulted in PSt with Mw/Mn = 1.15 at 53% monomer conversion.