The effect of polymer chain architecture on the adsorption properties of derivatised polyisobutylenes at the carbon/n-heptane interface

Adsorption isotherms for derivatised polyisobutylene (PIB) molecules from n -heptane onto activated carbon have been determined. Nine polyisobutylene s amples were studied: three different molecular weight groups (1000, 2000 an d 3000), with each molecular weight group having three different chain arch itectures, i.e. having one, two or three derivatised (azacarboxylate) termi nal head groups. The adsorbed amounts of the various PIBs were found to be dependent not only on their structure, but also on their solubility in n-he ptane. The difunctional PIE was found to adsorb the most strongly. The area s per molecule, particularly for the higher molecular weight samples, sugge st that the PIBs adsorb at the surface in an aggregated form, resulting in multilayers at higher coverages. Furthermore, all the PIBs are highly solva ted at the solid/solution interface. These two factors enable the polymer t o confer good steric stabilisation effects on the carbon dispersions. Compa red with previous studies of the adsorption of succinimide derivatives of P IBs onto carbon, the PIBs used in this work adsorb to a lesser extent, sugg esting that the azo head group does not provide as effective an anchor to t he particle surface as the corresponding succinimide. (C) 2000 Elsevier Sci ence B.V. All rights reserved.