Properties of Electropolymerized Dopamine and Its Analogues.

This work reports a study of electropolymerization kinetics, film thickness, stability, and antifouling properties of polydopamine (PDA) and its three analogues: poly(3-(3,4-dihydroxyphenyl)-l-alanine) (PL-DOPA), poly(5-hydroxytryptophan) (PL-5-HTP), and poly(Adrenalin) (PAdrenalin). It was observed that the number of the hydroxyl groups on the benzene ring and the type (primary vs secondary) of amine group significantly affect the electropolymerization kinetics and thus the thickness of the obtained polymer films. Monomers with two hydroxyl groups (except Adrenalin) resulted in films that were thicker (∼10-15 nm) than the one with only one hydroxyl group (PL-5-HTP) (∼5-8 nm) under similar conditions. Adrenalin containing a secondary amino group could not be deposited onto the ITO substrate, while the other three compounds containing a primary amino group completely covered the ITO. The PDA films had better electrochemical stability than the other films. No film showed stable antifouling surfaces against protein.