A composition including a plurality of oligomers including at least one selected from a repeating unit represented by Chemical Formula 1, a repeating unit represented by Chemical Formula 2, and a combination thereof; and at least one selected from a repeating unit represented by Chemical Formula 3, a repeating unit represented by Chemical Formula 3A, and a combination thereof; wherein at least a part of the plurality of oligomers includes at least one terminal end having an amino group, and wherein at least a part of the plurality of oligomers including at least one terminal end having an amino group is a diamine having a pKa value of equal to or less than 3 at 25° C.: wherein the variables in Chemical Formulae 1, 2, 3, and 3A are described in the specification.