Radical Copolymerization of Functional N-Substituted Maleimides with N-Vinyl-2-Pyrrolidone

Two functional N-substituted maleimide monomers, namely N-(4-carboxyphenyl)maleimide (CPMI) and N-(4-formylphenoxy-4′-carbonylphenyl) maleimide (FCPMI), were copolymerized with N Vinyl-2-pyrrolidone (NVP) at 90° C in the presence of 2,2′-azobisisobutyronitrile as initiator in dimethylformamide. The monomers reactivity ratios were calculated by extended Kelen–Tüdös and Mao–Huglin methods. The average reactivity ratios and Alfrey–Price Q and e Values were found to be r1 = 0.028, r2 = 0.347, Q1 = 0.035, e1 = 1.013 for CPMI/NVP system and r1 = 0.044, r2 = 0.060, Q1 = 0.145, e1 = 1.297 for the FCPMI/NVP system. The distribution of monomer sequences along the copolymer chain was calculated using a statistical method based on the obtained reactivity ratios. The thermal properties of the resulting copolymers were also investigated. These copolymers exhibit fairly high thermal stability with decomposition temperatures above 230° C. The effect of the N-substituents on the radical copolymerization of the above functional maleimides with NVP is discussed.