Polynitroxides from Alkoxyamine Monomers: Structural and Kinetic Investigations by Solid State NMR

A novel synthetic route toward poly(4-methacryloyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl) (PTMA) is described The polymerization of alkoxyamine-based monomers by atom transfer radical polymerization (ATRP) was investigated, as the polyalkoxyamine serves as the precursor for PTMA. The polydispersity indices (PDIs) and the kinetic data of the polymerization indicate a controlled reaction. The oxidative C-O bond cleavages of the polyalkoxyamine lead to PTMA. This transformation occurs with excellent yields, and it is possible to transfer the narrow PDIs of the prepolymer to PTMA. The material is characterized in detail using cyclic voltammetry in solution and magnetic susceptibility measurements as well as multinuclear solid state NMR and EPR spectroscopies. The conversion of the precursor polymer to the polynitroxide can be conveniently monitored by H-1 and F-19. magic angle spinning (MAS) as well as C-13{H-1} cross polarization (CP)-MAS NMR. In addition, the intermolecular interaction of the nitroxide side chain units in the polymer at high conversion can be detected and monitored by the observation of pronounced low frequency shifts.