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

Inverse gas chromatography (IGC) has been applied for the surface char acterization of styrene-4-vinyl pyridine (S-4VP) diblock polymers of v arying composition and of two rutile pigments. The latter were used as adsorbents for the polymers. Dispersion surface energies and acid-bas e interaction parameters were obtained from the IGC data. These show t hat the adsorbed layers form interphases where the local composition v aries with the mass of adsorbed polymer and also with the acid-base in teraction between rutile and the polymer. The results may be rationali zed by suggesting that the more basic 4VP moiety preferentially orient s to the acidic rutile surfaces, leaving surface compositions enriched in the less basic polystyrene (PS), which also has a lower surface en ergy. The effect was more pronounced when the strength of acid-base fo rces at the interface was increased. The experimental findings also pe rmit the calculation of thicknesses for the adsorbed interphases. Thes e were found to be in the range 30-90 nm, depending on the mass of ads orbed polymer and on its acid-base interaction with the adsorbing pigm ent surface.