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.