Adsorption of poly(vinyl alcohol) onto hydrophobic substrates. A general approach for hydrophilizing and chemically activating surfaces

The adsorption of poly(vinyl alcohol) onto hydrophobic surfaces is described. Three different commercial polymer film samples, poly(tetrafluoroethylene-co-hexafluoropropylene)(FEP), poly(ethylene terephthalate) (PET), and poly(4-methyl-1-pentene) (PMP), four different silicon-supported covalently attached monolayers prepared from tridecafluoro-1,1,2,2-tetrahydrooctyl-dimethylehlorosilane, n-decyldimethylchlorosilane, 10-(carbomethoxy)decyldimethylchlorosilane, and 3-[methoxy(polyethyleneoxy)]-propyltrimethoxysilane, and a gold-supported self-assembled monolayer of 1-dodecanethiol were used as adsorption substrates. The kinetics of the irreversible adsorptions and the concentration dependence of adsorbed layer thickness are reported for FEP and the fluoroalkyl monolayer. The adsorbed films render the surfaces of the substrates hydrophilic with advancing water contact angles ranging from 40 to 68degrees. PVOH films on hydrophobic alkyl and fluoroalkyl monolayers are 10-50 Angstrom thick, depending on solution concentration, and less thick on the less hydrophobic carbomethoxy-containing monolayers. Crystallization is implicated as a major driving force for adsorption as evidenced by infrared spectroscopy and electron diffraction. The supported PVOH thin films are stable in water at room temperature but dissolve in hot water. Cross-linking of the PVOH with glutaraldehyde causes the films to be stable to hot water.