1993 Volume 50 Issue 1 Pages 1-9
When poly (4-methyl-l-pentene) (PMP) and polystyrene (PS) films, which had been treated by a CF4 plasma discharge, are immersed in water, hydrophobic groups (-CF1, -CF2, -CF3) at the surface are reversed into an inert region. The dynamic characterization of the film surface was studied with respect to the contact angle of water and XPS spectra. When the treated film was immersed in water, the hydrophobic groups located up to 15Å from the surface, were reverted; they then migrated to an inert region beginning 15-30Å below the surface. These groups, then diffused into the inert region of the film, and could not be detected by XPS. Movement of the hydrophobic group was influenced by the segmental motion of the bulk molecule. This phenomenon was very vigorous above the glass transition temperature (Tg) . The diffusion rate of the hydrophobic group immersed in water at a below Tg differs from polymer to polymer. The diffusion coefficient of CF4-PMP is higher that of CF4-PS. The activation energies for the diffusion of the hydrophobic groups were 6 and 12 kcal/mol for CF4-PMP and CF4-PS, respectively.
