Adhesion and tribological property of Cu nanoparticles-doped hydrophobic polyelectrolyte multilayers

Hydrophobic polyelectrolyte multilayers (PEMs) doped with Cu nanoparticles and modified with fluoroalkylsilane were prepared by a series of reaction cycles, where the polyelectrolyte multilayers were constructed by alternate pipetting of the solutions of poly(diallyldimethylammonium chloride) and poly(sodium 4-styrene sulfonate) onto a spinning substrate (quartz slide or silicon wafer), and resultant PEMs-coated substrate was immersed in Cu2+ and NaBH4 solutions to allow nucleation of Cu nanoparticles. The relationship between the water wettability and tribological behavior of the as-prepared hydrophobic PEMs was studied. Results show that the wettability of the hydrophobic PEMs can be controlled by properly adjusting the reaction cycle. The adhesion and tribological behavior of the Cu nanoparticles-doped hydrophobic PEMs, excluding the one obtained at 12 reaction cycles, are closely related to their wettability. That is, the PEM film with stronger hydrophobicity has a lower surface energy, showing a lower friction and longer anti-wear life. Copyright (c) 2012 John Wiley & Sons, Ltd.