New possibilities with new surfactants Surfactants are not only widely used in everyday life, they’re also an important part of nanoscience research. Most existing surfactants are pure organic compounds, now researchers in the I-SURF project aim to develop a new class of surfactants containing inorganic constituents, which could pave the way towards new technological applications, as Professor Sebastian Polarz explains A type of
compound widely used in detergents and emulsifiers, surfactants are also an important tool in nanoscience research, allowing researchers to prepare and develop new nanoparticles. A surfactant molecule is made of two contrasting parts, as Professor Sebastian Polarz explains. “One part is the oilloving, or hydrophobic part – and this is typically an alkyl chain. The second part, which is called the head group of the surfactant, is the group which is compatible with water, it’s hydrophilic, and it gives you water solubility,” he says. Based at the University of Konstantz in Germany, Professor Polarz is the Principal Investigator of the I-Surf project, an ECbacked initiative which aims to synthesise a new class of inorganic surfactants. “Our idea was to ask; can we produce an entirely new class of surfactants?” he outlines. The vast majority of the surfactants are pure organic compounds, with an alkyl chain and a head group which are both purely organic. These surfactants are very interesting from a research point of view, because they show some fascinating self-organisation behaviour, now Professor Polarz and his colleagues aim to add additional functionality. “These surfactants should still have the interesting self-organisation properties we see in organic surfactants, but at the same time we want to add some additional functionality, which will be due to the inorganic constituents,” he explains. This research centres around modifying the head group of the surfactant, while leaving the alkyl chain unchanged. There are several different strategies for changing the head group. “One strategy is to have a head group
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ISURF Project Team (from left to right): Professor Sebastian Polarz, Alexander Klaiber, Dr James A. Odendal, Sebastian Sutter, Adrian Donner, Marius Kunkel, Stefanie Hermann.
which is purely inorganic. We do this with metal oxide entities,” outlines Professor Polarz. Another approach is to have a head-group which is able to bind metals, a so-called ligand. “This ligand coordinates to a metal, but then typically the head group will only contain one metal centre, rather than many,” continues Professor Polarz. “In our research we are investigating molecules with many metal centres and purely inorganic head-groups. But also, we are looking at surfactants where we have a ligand at the head group, which then coordinates the metal.”
you will eventually have a surfactant with a catalytically active head group,” he explains. These compounds would not normally show any self-organisation behaviour, but circumstances change when they are part of a surfactant. “We now see some self-organisation,” says Professor Polarz. “For example, one structure that is well-known from studies of surfactants are micelles, spherical objects which form in solution.”
Surfactant functionalities A core aim of the project is to develop molecules with specific redox, catalytic or magnetic functionalities. Professor Polarz and his colleagues have a wide variety of inorganic compounds which can be used as head groups in this research. “If you have an inorganic compound which is known for its catalytic properties, then
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