SURFACE FREE-ENERGIES OF ALKYLSILOXANE MONOLAYERS SUPPORTED ON ELASTOMERIC POLYDIMETHYLSILOXANES

Self-assembled monolayers (SAMs) of alkylsiloxanes on elastomeric polydimethylsiloxane (PDMS) are excellent model systems with which to study interactions between surfaces. The surface free energies of several monolayer-coated PDMS surfaces were determined by measuring the deformations produced from the contact between semispherical lenses and flat sheets of the elastomer under controlled loads. The contact deformations were analyzed using the theory of Johnson, Kendall, and Roberts (JKR) to estimate the surface free energies of the monolayer films, which were compared with the values obtained from contact angles. It is shown that the surface free energies of not only the apolar, but also the polar non-associative surfaces can be adequately described by considering only the dispersion forces. Polarity as obtained from the contact angles of water has no general significance in estimating the interfacial interactions across the polar nonassociative surfaces.