A polymer compound is formed by condensing a polyacrylic acid, a polyfunctional amine represented by the following general formula (1), and an aromatic monoamine. A chain structure constituted by the polyacrylic acid has free carboxyl groups and carboxyl groups to which the aromatic monoamines are bonded. Y is a straight-chain alkyl group having 1 to 4 carbon atoms, a phenylene group, or an oxygen atom. R1 and R2 are each independently one or more hydrogen atoms, a methyl group, an ethyl group, a trifluoromethyl group, or a methoxy group.