Joint theoretical experimental investigation of the electron spin resonance spectra of nitroxyl radicals: application to intermediates in in situ nitroxide mediated polymerization (in situ NMP) of vinyl monomers

Density functional theory (DFT) calculations have been performed to address the structure of nitroxide intermediates in controlled radical polymerization. In a preliminary step, the reliability of different theoretical methods has been substantiated by comparing calculated hyperfine coupling constants (HFCCs) to experimental data for a set of linear and cyclic alkylnitroxyl radicals. Considering this tested approach, the nature of different nitroxides has been predicted or confirmed for (a) the reaction of C-phenyl- N- tert-butylnitrone and AIBN, (b) N- tert-butyl-alpha-isopropylnitrone and benzoyl peroxide, (c) tert-butyl methacrylate polymerization in the presence of sodium nitrite as mediator, and (d) for the reaction of a nitroso compound with AIBN. Values of HFCC experimentally determined have been confirmed by DFT calculations.