SURFACE-PROPERTIES OF SOME STYRENE VINYL PYRIDINE DIBLOCK POLYMERS ADSORBED ON RUTILE

Inverse gas chromatography (IGC) has been applied for the surface characterization of styrene-4-vinyl pyridine (S-4VP) diblock polymers of varying composition and of two rutile pigments. The latter were used as adsorbents for the polymers. Dispersion surface energies and acid-base interaction parameters were obtained from the IGC data. These show that the adsorbed layers form interphases where the local composition varies with the mass of adsorbed polymer and also with the acid-base interaction between rutile and the polymer. The results may be rationalized by suggesting that the more basic 4VP moiety preferentially orients to the acidic rutile surfaces, leaving surface compositions enriched in the less basic polystyrene (PS), which also has a lower surface energy. The effect was more pronounced when the strength of acid-base forces at the interface was increased. The experimental findings also permit the calculation of thicknesses for the adsorbed interphases. These were found to be in the range 30-90 nm, depending on the mass of adsorbed polymer and on its acid-base interaction with the adsorbing pigment surface.