A compound having: one or more of the below repeat units, one or more terminating Ar—NH— groups bound to carbon radicals, and one or more terminating —H groups bound to nitrogen radicals. Each R is an organic group and each Ar is an aromatic group. The compound is not a thermoset. A method of: mixing an aromatic amine having the formula Ar—NH2 with a phthalonitrile compound, heating the mixture to form the compound described above, and cooling the mixture before the onset of gelation.