Attachment between a vitreous flat silica plate and an argon bubble in dodecyltrimethylammonium bromide solutions

Abstract

The stability and the rupture of intervening aqueous films formed between argon bubbles and a vitreous flat silica plate were investigated in aqueous solutions by changing the concentration of dodecyltrimethylammonium bromide (DTAB) in the presence of 0.001 M KNO 3 at solution pH levels of 5 and 10. The stability was assessed by measuring the lifetime of Newton interference fringes. The spontaneous rupture of the film, i.e., the attachment between bubbles and silica, occurred at surface coverages of DTAB on silica surfaces when the coverage was within the ranges 1–4% (pH 5) and 2–40% (pH 10). The analysis in terms of the conventional heterocoagulation theory does not account for the observed rupture, suggesting the existence of additional attractive forces due to hydrophobic interactions. The dependence of the hydrophobic interaction force constant, i.e., the value of C h in C hexp(− d/ d 0), where d is the surface separation and d 0 is the characteristic length, on the surface coverage of DTAB on silica surfaces is presented.