Isomeric bismaleimides and polyaspartimides

A study was conducted of the effects of meta‐para isomerism on the synthesis and properties of aromatic bismaleimides and polyaspartimides. Three isomers, 3,3′‐, 3,4′‐, and 4,4′‐diaminodiphenylmethanes (methylenedianilines), were used to prepare three isomeric bismaleimides. The bismaleimides then were reacted with their respective isomeric diamines in m‐cresol solution to give a series of isomeric polyaspartimides. The properties of each of the isomeric series were measured and compared. Strong flexible films were solvent cast from the two polyaspartimides derived from the 3,4′‐ and 4,4′‐diamines and their respective bismaleimides. Tensile properties of the films from the 3,4′‐diamine/3,4′‐bismaleimide combination polyaspartimide were equivalent to those from the 4,4′‐diamine‐derived polymer. That finding, together with that polymer's lower softening temperature and the nonmutagenic nature of the 3,4′‐diamine monomer, suggested a potential usefulness for 3,4′‐diaminodiphenylmethane as a replacement for 4,4′‐diaminodiphenylmethane in addition polyimides.