Radical Copolymerization of N-Vinylformamide with Methylvinylketone: An Approach to Iminium/Imine Ring Containing Polymers

The free radical copolymerization of N-vinylformamide (NVF) with methylvinylketone in water and the subsequent alkaline or acidic hydrolysis produce iminium structures containing polymers. It can be concluded from the copolymerization parameters (r(N-vinylformamide) = 0.02, r(methylvinylketone) = 0.50) that alternating copolymers are formed which contain few amounts with statistically arranged monomer sequences. The acidic hydrolysis of the copolymer results in a water-soluble polymer bearing five-membered iminium rings along the polymer chain. A water-insoluble polymer is generated under alkaline conditions also containing five-membered imine rings. The formation of the iminium ring polymer is attributed to the fact that generated free amino groups derived from NVF immediately react with the keto groups in the vicinity. The molecular structures of the obtained polymers are characterized by H-1-NMR, C-13-NMR, and IR spectroscopy. The assignment of the signals in the novel polymers are confirmed by model compounds.