Controlling the Permeability of Multilayered Polyelectrolyte Films through Derivatization, Cross-Linking, and Hydrolysis

Abstract

Partial Fischer esterification of poly(acrylic acid) allows tailoring of the hydrophobicity and charge density of multilayered films containing poly(allylamine hydrochloride) (PAH) and derivatized poly(acrylic acid) (d-PAA). As hydrophobicity and charge density strongly affect film permeability, control over these properties is vital for possible applications of PAH/d-PAA films as ion-separation membranes and sensors. The hydrophobicity of these films depends on both the extent of esterification and the nature of the derivatizing alcohol. Even though PAH/d-PAA films are composed of polyelectrolytes, the presence of hydrophobic ester groups results in advancing water contact angles as high as 101°. The hydrophobicity of these coatings allows them to effectively passivate underlying electrodes as shown by minimal peak currents in cyclic voltammograms (CVs) of Ru(NH3)63+ and Fe(CN)63-. Cross-linking of hydrophobic PAH/d-PAA films via heat-induced amidation stabilizes coatings over a wide pH range but does no...