Synthesis, characterization, and computational study of potential itaconimide-based initiators for atom transfer radical polymerization

Abstract

Atom transfer radical polymerization (ATRP) has been a promising technique to provide polymers with well-defined composition, architecture, and functionality. In most of the ATRP processes, alkyl halides are used as an initiator. We report the synthesis of three possible potential initiators, N-phenyl(3-bromo-3-methyl)succinimide, N-phenyl(3-bromo-4-methyl)succinimide, and N-phenyl(3-bromomethyl)succinimide for ATRP of N-phenylitaconimide (PI) and methyl methacrylate (MMA). These functionalized alkyl halides, having structural similarity with PI, were characterized by FTIR, HRMS, ¹H, ¹³C NMR spectroscopy, and elemental analysis. The equilibrium constants for the ATRP activation/deactivation process (K_ATRP) of these alkyl halides as well as a commercial ATRP initiator (ethyl-α-bromoisobutyrate) were determined using UV-Vis-NIR and DOSY NMR spectroscopy. Alternatively, these compounds and similar alkyl halides (R-X) were investigated using density functional theory for their possible chain initiation activity for the ATRP process. The B3LYP functional and 6-31+G(d)/LanL2DZ basis set was used for the prediction of geometries and energetics associated with the homolytic R–X bond dissociation. The relative value of K_ATRP and its variation with system parameters (such as substituent, temperature, and solvent) was investigated. We found a good agreement between the experimentally determined and theoretically calculated K_ATRP values. Our experiments show that the newly synthesized initiator N-phenyl(3-bromo-3-methyl)succinimide performs better than the commercially available initiator ethyl-α-bromoisobutyrate for the atom transfer radical copolymerization of PI and MMA.