The photo is sourced from bbcream.ru
Brown and red algae contain large amounts of alginic acid, a polymer with a viscous, rubber-like structure. The salts of this acid with various metals – alginate hydrogels – are used as thickeners by the food industry and for 3D printing biocompatible medical devices. The most popular method to produce alginate hydrogels is to add an iron salt to an alginate solution. Such a composition solidifies almost instantly, resulting in the material distinguished by a very heterogeneous structure (gel-like – outside and liquid – inside) having a bad effect on its mechanical properties.
To solve this problem, a group of the Russian scientists tried to replace iron salts with a complex compound of the same metal decaying under the impact of light. Experiments showed that the mixture of these components remains liquid for a long time (up to 30 days) if in the dark. However, when illuminated, the gel begins to solidify due to chemical reaction between the polymer and the iron compound: iron ions are released from the latter and are embedded between the alginate molecules, building their network. As a result, in just 30 minutes, a transparent solution turns into a solid substance of orange colour provided by the iron ions released from the complex compound.
Applying their own developed technique, the authors of the study obtained four variants of alginate hydrogels with different iron content. The materials, in which the proportion of iron complex was equal to the amount of polymer, were ten times stronger and more resistant to moisture than the samples where metal was four times less. This is due to a large number of rigid cross-links between the polymer filaments formed by iron ions.
The strongest hydrogel was tested as an adhesive for glass. The scientists applied a small amount of the solution between two glass panes and left it in the light for 30 minutes. Then they tested the bond strength by applying a load comparable to the pressure of 1 kilogram per square centimetre to the seam. The latter withstood the load, as the new technology ensured that the adhesive was evenly distributed between the surfaces and prevented the compound from drying out ahead of time.
“The materials we have obtained can be used as adhesives, as we have shown experimentally as well as in creation of medical materials, for example, for restoration of the damaged bone tissues. However, first we will need to conduct additional research into a potential toxicity of the iron complex for the human body,” the Russian Science Foundation quotes Dmitry Perekalin, Doctor of Chemical Sciences, a leading researcher at the Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences.
