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-dimethylchlorosilane, 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 68°. PVOH films on hydrophobic alkyl and fluoroalkyl monolayers are 10−50 Å 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.

A thermodynamic theory is developed of the elasticity of two-component monolayers consisting of an insoluble surfactant and a soluble cosurfactant. Deriving general expressions for the effective stretching and bending elastic moduli of the monolayer, we find the exchange of cosurfactant with the environment to reduce both moduli. A simple model of the monolayer is introduced specifying the dependence of the bending rigidity and the bending moment on the numbers of surfactant and cosurfactant molecules. Numerical estimates of the effect of a cosurfactant show that the stretching elastic modulus remains positive but may be reduced by an order of magnitude, while the bending rigidity can become even negative in certain conditions.

The adsorption of poly(vinyl alcohol) (PVOH) from aqueous solutions to a silicon-supported fluoroalkyl monolayer is described. Thickness, wettability, and roughness of adsorbed films are studied as a function of polymer molecular weight, degree of hydrolysis (from the precursor, poly(vinyl acetate)), polymer concentration, salt type and concentration, and temperature. The data suggest a two-stage process for adsorption of the polymer: physisorption due to a hydrophobic effect (decrease in interfacial free energy) and subsequent stabilization of the adsorbed layer due to crystallization of the polymer. Adsorption of lower-molecular-weight polymers results in thicker films than those prepared with a higher molecular weight; this is ascribed to better crystallization of more mobile short chains. Higher contents of unhydrolyzed acetate groups on the poly(vinyl alcohol) chain lead to thicker adsorbed films. Residual acetate groups partition to the outermost surface of the films and determine wettability. Salts, including sodium chloride and sodium sulfate, promote adsorption, which results in thicker films; at the same time, their presence over a wide concentration range leads to formation of rough coatings. Sodium thiocyanate has little effect on PVOH adsorption, only slightly reducing the thickness in a 2 M salt solution. Increased temperature promotes adsorption in the presence of salt, but has little effect on salt-free solutions. Evidently, higher temperatures favor adsorption but cause crystallization to be less thermodynamically favorable. These competing effects result in the smoothest coatings being formed in an intermediate temperature range.

Covalently attached, soft poly(vinyl alcohol) (PVA) hydrogel films containing silver particles were prepared on solid biodegradable poly(l-lactic acid) (PLLA) samples by a multistep procedure involving oxygen plasma treatment, UV-initiated graft polymerization, and chemical grafting methods. The modification steps were followed and verified using attenuated total reflection infrared spectroscopy and X-ray photoelectron spectroscopy. 2-Hydroxyethyl methacrylate (HEMA) was graft polymerized from the surface of oxygen plasma-treated PLLA film samples and the alcohol functionality in the grafted polyHEMA chains was oxidized using pyridinium dichromate to obtain an aldehyde-rich surface. PVA was then grafted onto this surface using acid catalysis (acetal formation). The "freeze/thaw method" was used to form a PVA hydrogel layer that incorporated the covalently grafted PVA chains in the physically cross-linked gel. This composite film (PLLA-PVA(gel)) was doped with silver ions, which were reduced to silver using NaBH(4). Scanning electron microscopy of cross sections of PLLA-PVA(gel) indicates robust attachment of the PVA hydrogel layer to the PLLA film. PLLA-PVA(gel/Ag(0)) film samples exhibit both antibacterial and reduced cell adhesion properties due to the antibacterial properties of silver nanoparticles and high water content, respectively. This method provides a route to mechanically sound biodegradable materials with tunable soft material surface properties. Potential applications in tissue engineering and biomedical devices are envisioned.