The present invention relates to a method for selective removal of a tert-butyl ester group from a hydrolytically unstable polymer to form a new polymer composition having a free carboxylic acid group in place of said tert-butyl ester group, said method comprising dissolving said hydrolytically unstable polymer in a solvent comprising an amount of an acid having a pKa from about 0 to about 4 that is effective to selectively remove by acidolysis said tert-butyl ester group to form said new polymer composition having a free carboxylic acid group.
