화학공학소재연구정보센터
Langmuir, Vol.14, No.15, 4011-4016, 1998
Indirect evidence for non-DLVO forces in emulsions
We prepare quasi-monodisperse oil-in-water emulsions stabilized by tetradecyltrimethylammonium bromide and observe their behavior at various surfactant and salt concentrations. In the absence of salt, we observe a succession of dispersed and flocculated states as the surfactant concentration is increased. At constant surfactant concentration, increasing the amount of a monovalent salt (KF, KCl, KBr,...) from 0 to 2 M leads to flocculation followed by a reentrant dispersed state. We examine the influence of the chemical nature of the counterion and temperature on the flocculation and redispersion phenomena. We also investigate the phase behavior of quasi-monodisperse emulsions in the presence of a divalent salt (MgSO4). Our observations reflect the predominance of different non-DLVO surface forces (structural, hydration, "thermal fluctuations" forces) in controlling-the stability of emulsions at high salt and/or surfactant concentrations.