Interactions and mobility of copper(II)–imidazole-containing copolymers

Poly(1-vinylimidazole-co-methyl methacrylate) copolymers (PVM) were obtained from copolymerization of 1-vinylimidazole and methyl methacrylate with 2,2′-azobisisobutyronitrile as an initiator. The formation of random copolymers was substantiated by the glass transition temperature (Tg) and the proton spin–lattice relaxation time in the rotating frame (TH1ρ). Cu(II)-PVM complexes were prepared by mixing tetrahydrofuran solution of PVM and copper sulfate solution. The formation of coordination bond between PVM and Cu2+ ions was studied using differential scanning calorimetry, infrared and 13C solid-stated nuclear magnetic resonance spectroscopy. A single composition dependent Tg was obtained for the PVM copolymers, and that increased with increasing VI content. The Tg value of the Cu(II)-PVM complex was much higher than that of the PVM copolymer with the same composition. The TH1ρ of the VI units and MMA units in the copolymers and complexes had one value, and that in the complexes was much lower than that in the copolymers. The dramatic decrease in TH1ρ for the Cu(II)-PVM complexes was due to Cu(II) complexation and electron–nuclear dipolar interactions.