UV-induced polymerization of maleimides in solution

Maleimide and N-ethylmaleimide were irradiated in various solvents with a high pressure mercury lamp at 30°C. The polymerization of maleimides is promoted in the presence of hydrogen donating solvents such as tetrahydrofuran, 1,4-dioxane, ethanol and basic solvents such as dimethylformamide, dimethyl acetamide, pyridine. ESR spectra suggest that a radical mechanism is responsible for the polymerization in the former solvents and an anionic mechanism in the latter solvents.