Neutron Reflection from Mixtures of Sodium Dodecyl Sulfate and Dodecyl Betaine Adsorbed at the Hydrophobic Solid/Aqueous Interface

The effects of the addition of the polyelectrolyte, poly(ethyleneimine), on the adsorption of mixed surfactants of sodium dodecylsulfate and dodecyldimethylaminoacetate at the air–water interface

“…An application of RST [10] to the surface tension data indicates a large negative interaction parameter, b, $À10 [30,31]. At the air-water interface and at the hydrophobic solid surface [31] NR measurements show that this results in a strong partitioning of the dodecyl betaine to the interface compared to the solution composition, but consistent with a b $ À2.0. The difference between the ST and NR data was attributed to changes in hydration on mixing which are not accounted for in the pseudo phase approximation.…”

“…In solution and at the interface dodecyl betaine/SDS surfactant mixtures, in the absence of polyelectrolyte, strongly interact and show a strong departure from ideal mixing [30,31]. An application of RST [10] to the surface tension data indicates a large negative interaction parameter, b, $À10 [30,31].…”

“…The deuterated SDS (d-SDS, C 12 D 25 SO À 4 Na þ ) was synthesised as described previously and purified prior to use by recrystallisation from ethanol [34]. The protonated and deuterated dodecyl betaines (C 12 H 25 N + (CH 3 ) 2 CH 2 COO, C 12 D 25 N + (CH 2 ) 2 CH 2 -COO) were synthesized and purified, as described elsewhere [31,35]. The chemical purity of the surfactants was checked using surface tension measurements, and no minimum in the surface tension was observed at the cmc.…”

“…It has been previously established [30,31] that the SDS/dodecyl betaine mixture has a strong synergistic interaction in solution and at the interface. From recent studies [17,18,29] it is also evident that SDS interacts strongly with the PEI, and that there is a strong pH dependence to the nature of that interaction.…”

Adsorption of mixtures of nonionic sugar-based surfactants with other surfactants at solid/liquid interfaces

“…Various interactions between solid substrates and cationic-nonionic or nonionic-nonionic surfactant systems have been reported [3][4][5][6][7][8].…”