Abstract
Self-assembly on a polycrystalline aluminum substrate of two sulfur-containing alkylphosphonic acids, CH3 –(CH2)11–S– (CH2)2 –PO(OH)2, and CF3 –(CF2)7 –(CH2)2 –S–(CH2)2 –PO(OH)2, has been compared with CH3 –(CH2)15 –PO(OH)2. The reaction of the phosphonic head groups with the hydroxyls at the alumina surface to form phosphonates was studied with X-ray photoelectron spectroscopy (XPS) andpolarizationmodulation infrared reflection-absorption spectroscopy (PM-IRRAS).Barrier effects of the resulting layerswas assessed by electrochemical polarization curves.With the conditions used in the present work for the self-assembly reaction, it appears that the sulfur-containingmolecules do not perform as well as CH3 –(CH2)15 –PO(OH)2 in terms of film quality. Questions are raised about the possibility that the sulfur-containingmolecules could undergo cleavage during surfacemodification.