Robin Benedix

2023

1. Benedix, R.R., Botsch, S., Preisig, N., Kovalchuk, V., Jessop, P.G., Stubenrauch, C.: Influence of a CO2-switchable additive on the surface and foaming properties of a cationic non-switchable surfactant. Soft Matter. 19, 2941–2948 (2023). https://doi.org/10.1039/D3SM00273J.
   • Abstract
   • Link

   Abstract

   Switchable materials in general and CO2-switchable materials in particular are of great interest in environmental research. The replacement of common non-switchable materials (solutions, solvents, surfactants, etc.) with their switchable counterparts has a great potential to make processes more environmentally friendly by enhancing reusability and circularity and thus reducing energy costs and material consumption. Inspired by this, the present work deals with the surface and foaming properties of aqueous solutions of a non-switchable surfactant in presence of a CO2-switchable additive. A 1 : 1 and a 1 : 5 (molar ratios) mixture of the non-switchable surfactant C14TAB (tetradecyltrimethylammonium bromide) and the CO2-switchable additive TMBDA (N,N,N,N-tetramethyl-1,4-butanediamine) were investigated. It was found that surface properties, foamability, and foam stability can be changed by switching the additive with CO2 as a trigger. This observation can be explained by the fact that TMBDA is surface active in its unprotonated, i.e. neutral form, which disturbs the tight packing of the surfactant molecules on the surface. As a consequence, foams generated with surfactant solutions containing the neutral TMBDA are less stable than their TMBDA-free counterparts. On the other hand, the switched diprotonated additive is a 2 : 1 electrolyte with hardly any surface activity and thus does not affect surface and foam properties.

   Link

   http://dx.doi.org/10.1039/D3SM00273J
2. Benedix, R.R., Poole, H., Zauser, D., Preisig, N., Jessop, P.G., Stubenrauch, C.: Surface and foaming properties of an anionic CO2-switchable tail surfactant. Tenside Surfactants Detergents. 60, 269–276 (2023). https://doi.org/doi:10.1515/tsd-2023-2524.
   • Abstract
   • Link

   Abstract

   CO2-switchable materials in general and CO2-switchable surfactants in particular are of great interest in environmental research. There is a great potential to make processes more environmentally friendly by enhancing reusability and circularity and thus reducing material costs and energy consumption by replacing common non-switchable surfactants with their switchable counterparts. Inspired by this, the present work deals with the surface and foaming properties of aqueous solutions of the novel anionic CO2-switchable tail surfactant sodium 4-(methyl(octyl)amino)butane-1-sulfonate. In the presence of N2, the unprotonated surfactant is able to stabilize foams. By switching, i.e. by protonating the CO2-responsive trialkyl amine group in the surfactants hydrocarbon chain, the amphiphilic nature of the surfactant is reduced which is indicated by an increase of the plateau surface tension and a higher CMC compared to the non-protonated surfactant. Furthermore, the ability of the protonated surfactant to stabilize foams is reduced.

   Link

   https://doi.org/10.1515/tsd-2023-2524