Calorimetric determination of heat of polymerization of maleimide

The heat of polymerization of maleimide, a new rea,tive monomer was measured in an isothermal distillation calorimeter working a t 74.5°C. A value of 21.0 ± 0.5 kcal./mole has been obtained as the −ΔH88 in polar solvents, acetonitrile and dimethyl formamide in which the intermolecular association for the monomer (and polymer) has a minimum. This value is appreciably lowered (by about 5 kcal) in chlorobenzene, a relatively nonpolar medium. The high enthalpy of polymerization of maleimide accounts for its remarkable polymerizability and is partly attributed to the changes in the internal strain of the monomer ring accompanying polymerization.