Radical and anionic homopolymerization of maleimide and <i>N</i>‐<i>n</i>‐butylmaleimide

Abstract

Abstract The rate of homopolymerization of maleimide has been measured in dimethylformamide solution at 60°C. in the presence of azobisisobutyronitrile; it has been compared to that of N‐n ‐butylmaleimide. The overall rates of polymerization are equal to R p = k [M] 1.1–1.2 [In] 0.8 for maleimide, and R p = k '[M] [In] 0.5 for the N ‐substituted imide. The difference of behavior has been interpreted on the basis of an intramolecular tautomery of the terminal group of the maleimide growing chain and the formation of a resonance‐stabilized succinimidyl radical. The relative ease of polymerization of these monomers and of maleic anhydride has been discussed. In the presence of sodium tert ‐butoxide at 20°C. in dimethylformamide solutions, maleimide polymerizes with hydrogen isomerization. The percentage of N ‐substituted isomerized units was evaluated at 70–75% by measurement of the rate of hydrolysis in 0.005 N sodium hydroxide and comparison with succinimide and N ‐butylsuccinimide. N‐n ‐butylmaleimide undergoes ring opening together with anionic polymerization in the presence of sodium tert ‐butoxide at 20°C. and butyllithium at ‐40°C. Unlike the radical‐initiated polymerization, it was impossible to obtain anionic copolymers of maleimide and N ‐butylmaleimide with acrylonitrile and methyl methacrylate.