In situ kinetics and thermodynamics of polymer adsorption on chemically modified silica

In situ Fourier transform infrared (FT-IR) spectroscopy in an attenuated total reflection mode has been employed to examine the chemical modification of ozone-cleaned, native oxide on single crystal Si(100). This planar model for silica is subjected to solution modification using silane reagents which impart variable polarity to the modified surface through different termini of the modifier. These chemical modifications are followed in real time using FT-IR as a diagnostic of surface preparation; either by examining the appearance of a band for an IR chromophore of the modifier which is attached, or by monitoring the loss of the surface silanol groups consumed in the reaction. Following modification, polymer solutions (acrylates, siloxanes) are introduced into the cell and the dynamics of the adsorption followed by a chromophore of the polymer. Not only can the total amount of bound polymer be determined, but also in cases of strong interactions between the polymer and surface modified (e.g., OH···O = C) the bound fraction can be determined. Correlations between surface polarity and these experimentally determined quantities give insight in to the configuration(s) of the adsorbed polymers.