ore groups of at least one kind selected from the group consisting of phenolic hydroxyl group, carboxyl group, thiophenol group, and sulfonic group; R3 is a divalent organic group having no phenolic hydroxyl group, carboxyl group, thiophenol group, or sulfonic group; and R2 and R4 each are a tetravalent organic group constituting a tetracarboxylic acid or a derivative thereof when R1 has one or mo