Chain-extending functional polyimides by dipole reactions

Aromatic polyimides with various functional end-groups such as --CH.dbd.CH.sub.2, --C.tbd.CH, --CN and --CHO are chain-extended (molecular weight increased) by reacting the functional groups with aromatic bis-dipoles. A representative bis-dipole is 1,4-benzene-dinitrile oxide. These polyimides can be shaped and formed prior to chain extending. The aromatic polyimides appropriate for chain-extending are formed by the reaction of aromatic dianhydrides, aromatic amines and monoamines which contain the functional groups.