Interaction forces between α-alumina fibers with coadsorbed polyelectrolyte and surfactant

Ineke Muir, Laurence Meagher, Michelle Gee

Research output: Contribution to journalArticleResearchpeer-review

15 Citations (Scopus)

Abstract

Surface interactions between two α-alumina surfaces, at the point of zero charge, with coadsorbed poly(styrene sulfonate) (PSS) and cetyltrimethylammonium bromide (CTAB) have been measured using the atomic force microscope. The interaction forces were found to be dependent on the order of addition of the polyelectrolyte and surfactant. When CTAB was sequentially added to a preadsorbed PSS layer, the surfaces were observed to jump into contact due to an attractive bridging force that was not present in the absence of CTAB. This indicates that the addition of CTAB alters the PSS adsorbed conformation such that there is significant tailing of the PSS chains away from the interface facilitating a bridging force. In contrast, when PSS and CTAB were coadded, no bridging attraction was measured, implying a more compact adsorbed layer and, most likely, a greater surface excess of the PSS-CTAB complex. The surfaces did exhibit an adhesive force when retracted due to PSS chain entanglement that occurred when the adsorbed layers were in contact. At an electrolyte concentration of 10-1 M KBr, sequential addition of CTAB to a preadsorbed PSS layer led to a marked reduction in the adhesion between the two surfaces, as compared to that measured under lower electrolyte conditions, and there was no attractive jump into contact. This implies that the PSS remained in a relatively flat surface conformation due to the small degree of PSS-CTAB complexation. In the coaddition case, the adsorbed species at high salt behaved like an uncomplexed PSS chain under the same solution conditions. These data show that a salt concentration of 10-1 M KBr is sufficient to restrict PSS-CTAB association significantly.

Original languageEnglish
Pages (from-to)4932-4939
Number of pages8
JournalLangmuir
Volume17
Issue number16
DOIs
Publication statusPublished - 7 Aug 2001
Externally publishedYes

Cite this