Figure 1: Surfactants attach themselves to liquid interfaces and reduce their interfacial tension.
Surface-active substances, also called surfactants, are composed of a hydrophilic and a hydrophobic part. They prefer to attach themselves to liquid interfaces and reduce the interfacial tension of that interface. In practice, surfactants are used, for example, to achieve a good washing effect or to produce emulsifiers for the food industry.
Surfactants are surface-active substances. They influence the interaction of two, often liquid, substances at their interface. A surfactant molecule consists of a polar head group and a non-polar hydrocarbon chain (see Figure 2). The polar part of the molecule can interact strongly with polar substances, such as water. This is why this part of the molecule is also called hydrophilic, i.e., water-loving. The non-polar part of the molecule can interact strongly with non-polar substances, such as oil, which is why it is called lipophilic, i.e., fat-loving, or hydrophobic.
Figure 2: A surfactant consists of a non-polar hydrocarbon chain (red) and a polar head (blue).
One way to classify surfactants is by the charge of their head group:
Due to their bipartite structure, surfactants prefer to attach to interfaces, where they find energetically favourable conditions. On a water surface, for example, the surfactants orient themselves in such a way that the polar head group points into the water and the non-polar hydrocarbon chain points into the gas phase, for example into the ambient air (see Figure 3). Due to their bipartite structure, surfactants can interact well with both phases. They thus serve as mediators between the atoms or molecules of the two phases.
mediators
Figure 3: Surfactants accumulate at the interface, because they find energetically favourable conditions there.
The accumulation of surfactants at the interface of two phases influences the properties of the interface. Specifically, the addition of surfactants reduces the interfacial tension. This means that less energy is needed to increase the interface. The addition of surfactants therefore facilitates the mixing of non-polar and polar phases.
A well-known example is that of a paper clip in a glass of water. In pure water, the paper clip, if placed carefully, can float on the water surface due to the high surface tension of water. If you add a surfactant - such as washing-up liquid or soap - the surface tension drops and the paper clip sinks.
In industrial practice, the lowering of the interfacial tension through the addition of surfactants results in versatile applications.
Contact us nowmail_outline
Tensiometers of the DCAT series
Measurements of surface and interfacial tension as well as the critical micelle concentration
DCAT extension: LDU 25 liquid dosing unit
Automatic generation of concentration series
Application laboratory
Tests and contract measurements directly from the manufacturer
You did not agree to the use of Site Search 360 or your browser prevents the use of cookies. If you want to change your decision regarding the use of Site Search 360, please refer to our privacy policy
Our own first-party cookies solely store the decisions you make regarding third-party services and cookies using the following form. For more information on our first-party cookies please refer to our privacy policy.
We use services provided by third-parties. With the following form you can agree or disagree to the use of these third-parties. For more information on these services and how they may use your information, please refer to our privacy policy. There you can also review the decision you made.
Do you agree to the use of Google Analytics?
Do you agree to the use of Site Search 360?