Surfactants are key components in many products and processes where their surface-active properties are needed, and in such applications, the surfactant-surface interaction dynamic could be critical. Here we show how the surfactant interaction with surfaces can be analyzed in a time-resolved manner at the nanoscale.
Monitoring and quantification of surfactant adsorption to a surface
In several products and processes, such as in detergents and cleaning agents, in pharmaceutical formulations, in oil recovery, CMP, as well as in mining, the surfactant-surface interaction dynamic is critical to the application. It is therefore relevant to understand these processes at the nanoscale. In this study, QSense QCM-D, which is a surface-sensitive real-time technology, was used to characterize the surfactant adsorption. Two different surfactants were analyzed, Triton-X and ßOG. The focus of the QCM-D measurements was to analyze:
the surfactant adsorption dynamics
the amount of surfactant adsorbed, and
the stability of the surfactant-surface interaction
The surface interaction dynamics differ between the two surfactants
The results, Figure 1, show that both Triton X-100 and ßOG adsorb to the surface. However, the time to saturation differs between the two, and Triton X-100 reaches saturation faster that ßOG even though the concentration was lower. The results also show that ßOG forms a thicker layer than the Triton X-100 and that more ßOG than Triton X-100 remains at the surface after rinse.
Figure 1. Time-resolved thickness change as the surfactants, Triton X-100 and ßOG, adsorb to the sensor surface.
Key takeaways from the time-resolved surface interaction analysis:
Triton X-100 reaches saturation faster than βOG
βOG forms a soft film
Triton X-100 forms a rigid film
βOG forms a thicker layer than Triton X-100
In several products and processes, the surfactant-surface interaction dynamic is important and therefore relevant to understand at the nanoscale. QCM-D analysis provides information on surfactant-surface interaction processes under a variety of different substrate- and experimental conditions. Via this quantification of the surfactant-surface interaction, conclusions can be drawn regarding the suitability of surfactants in different applications.
Gabriel Ohlsson has been working both as application scientist and sales manager at Biolin Scientific. He did his PhD in engineering physics and has spent a lot of time to develop sensing technologies for soft matter material applications. One of his main tools during this research has been the QCM-D technology.