Self-healing materials based on polymers are one of the “miracles” of modern chemistry. Research on self-healing materials is being conducted by the SUSU materials scientists and power engineers in a consortium with colleagues from the Institute of Chemistry of St Petersburg University as part of the implementation of the Priority 2030 program at the university.
“A self-healing material is capable of restoring its structure after mechanical stress or other types of damage,” says Candidate of Sciences (Chemistry), Senior Research Fellow of the SUSU Multiscale Modelling of Multicomponent Functional Materials Laboratory Gennadiy Makarov. “It is especially interesting if it does this on its own, without external influences - autonomously. But this does not happen all the time; sometimes, for example, ultraviolet radiation, heating, or exposure to chemical reagents is required.”
Colleagues from the “Functional Polysiloxanes and Materials Based on Them” research group headed by Doctor of Sciences (Chemistry), Professor of the Department of Chemistry of Macromolecular Compounds Regina Islamova (Institute of Chemistry of St Petersburg University) synthesized a number of self-healing or self-restoring silicone materials for protection against electrical breakdown. In particular, Candidate of Sciences (Chemistry), Senior Research Fellow of the Department of Chemistry of Macromolecular Compounds of St Petersburg University Konstantin Deryabin was engaged in obtaining metal-polymer complexes based on pyridine-containing copolysiloxanes.
The new polymer itself is a “jelly-like substance”. But if you add certain atoms of transition metals (nickel, cobalt, iron), you can obtain different materials: from gel to “rubber”. All that remains is to dry them and obtain a film.
The material itself has no special mechanical strength. But if you cut it, then after about 1-2 days at room temperature, the cut will close. At the same time, the effectiveness of self-healing for a number of samples reaches more than 90%.
“The thing is that this new material is complex: it combines a polymer matrix and metal ion complexes. At the same time, it can be both elastic and gel-like, so it is hardly possible to trace and understand what happens during self-reduction with macromolecules by experimental means. The only way is to model structural changes at the atomic-molecular level. We have built a model of the continuous structure of the polymer in three variants differing in nickel content,” says Gennadiy Makarov. “The strength of the material and its other physical and chemical characteristics depend on the nickel content. Perhaps the most interesting finding here is that the water included in the material is able to form clusters that are attracted to nickel ions, and these clusters are not isolated, but are connected by something like the thinnest chains, 1-2 water molecules thick.”
Inside the hydrophobic material, which is what the sheath of an electric cable should be, there is a “secret” hydrophilic network along which nickel and chlorine ions can move.
What properties does this structure provide? How does it influence the self-healing mechanism? How will it change the electrical conductivity, which is very important for an insulating material? Scientists will have to figure all this out.
So far, the scientists have published what they have already discovered in the highly rated international Journal of Inorganic and Organometallic Polymers and Materials. In their model, they took not only the physicochemical characteristics into account, but also described in detail the structural specifics of the polymer chains and explained the process of their twisting.
At the initial stage of contacts between the research teams of the Institute of Chemistry of St Petersburg University and SUSU, they found out that the new material has electrical strength sufficient for its use as insulation.
“As part of a consortium with the “Functional Polysiloxanes and Materials Based on Them” research group headed by Doctor of Sciences (Chemistry), Professor of the Department of Chemistry of Macromolecular Compounds Regina Islamova (Institute of Chemistry of St Petersburg University), an interdisciplinary team of the SUSU materials scientists and power engineers have begun research into the possibilities of using the innovative material for electrical products,” says First Vice-Rector – SUSU Vice-Rector for Research, Doctor of Sciences (Engineering) Anton Korzhov.
Samples of the new polymers with different compositions are synthesized in St. Petersburg, and experiments on the resulting variations of the samples are conducted at the SUSU laboratories.
“The team of scientists from the Department of Power Stations, Grids, and Electric Power Systems is developing electrical testing methods and conducting research into changes in dielectric properties as a result of electrical breakdown of this material,” explains Candidate of Sciences (Engineering), Associate Professor of the Department of Power Stations, Grids, and Electric Power Systems Mikhail Dzyuba.
As part of the joint research on the interdisciplinary project at SUSU, an experimental setup for electrical breakdown with current limitation through material samples was created. The key design feature of the setup is the minimized cell volume, which allows to analyse the samples of the new materials synthesized in limited quantities.
The proposed approach allows to observe the self-healing process in small-volume polysiloxane samples by longitudinal visualization of defect evolution over long time scales.
The developed experimental setup also allows to study the phenomena preceding the electrical breakdown. To analyse the process of treeing (defect) channel development in the sample structure, video recordings of the interelectrode space were made, according to which repeated formation and disappearance of electrical defects occurred during exposure to the electric field.
“A major scientific task, within the framework of which this project can yield results, lies in the matching of the stages of modelling and targeted synthesis of materials with specified properties. What is the main scientific problem here? There are models of matter that are made by material scientists, there are models of breakdown and recovery that we, power engineers, make,” speaks on the specifics of the work Candidate of Sciences (Physics and Mathematics), Associate Professor Valeriy Safonov. “When we can combine the results of our research, it will be clear what exactly needs to be changed in the structure of the matter so that the process goes as desired and the insulation is effective.”
As part of joint research, the scientists of the SUSU Department of Power Stations, Grids, and Electric Power Systems proposed a new approach that allows to analyse the effectiveness of self-healing of transparent silicone materials with defects in the form of bubbles that occur after a low-power electrical breakdown.
“This research is unique, most of all, due to its comprehensiveness,” says the Deputy Head of the Laboratory, Doctor of Sciences (Chemistry) Ekaterina Bartashevich. “A subtle combination of relationships between several groups of scientists responsible for different scientific tasks and different stages of material development is built. One part of the team studies the self-healing properties of materials at the fundamental level. These are our colleagues from St Petersburg University: chemists Regina Islamova, Konstantin Deryabin, Anna Miroshnichenko and colleagues from SUSU: materials scientists Gennadiy Makarov and Tatyana Makarova (engaged in digital materials science). The second part of the team includes power engineers Valeriy Safonov, Mikhail Dzyuba, Aleksandr Prokudin. They represent the practical part – testing innovative materials for electrical strength.”
Thus, a technological chain is being built within the consortium in the project. It already enables fundamental science to reveal the nature of non-obvious phenomena.
“Our colleagues from St. Petersburg are responsible for the organic synthesis of polymers in the project. They have excellent developments, original ideas, they are experienced researchers, they have a powerful experimental base, and they have the capabilities of fundamental measurements, synthesis, which is very important for research.
SUSU has a very talented group of power engineers responsible for analysing the effectiveness of insulating materials. In our research, high-precision equipment, precisely tuned to very small volumes of matter, is very important. Power engineers are responsible for it.
Candidate of Sciences (Engineering), Associate Professor of the Department of Power Stations, Grids, and Electric Power Systems Aleksandr Prokudin assembles a cell where tests are conducted for ultra-small volumes of matter.
In addition, at SUSU we study the nature of self-healing of materials at the atomic-molecular level. Molecular dynamic models are created by Gennadiy Makarov and Tatyana Makarova. Candidate of Sciences (Engineering), Junior Research Fellow of the Multiscale Modelling of Multicomponent Functional Materials Laboratory Tatyana Makarova is engaged in algorithms for constructing the structure of polysiloxanes.
The most important thing in our project is a precisely constructed technological chain of interaction between representatives of fundamental and applied science.
Within the framework of this consortium, we are learning to transmit fundamental knowledge. Modelling the properties of substances allows us to reveal the nature of self-healing, immediately bringing it closer to the tasks of the technological process and modernization of the material so as to improve its properties already in insulating products.
If this technological chain works, we will be able to achieve interconnections between fundamental research and applied tasks and achieve real results. This is our goal at the moment,” Ekaterina Bartashevich summarizes.
The project is being implemented at SUSU as part of the fulfilment of the Strategic Technological Project No. 2 “Fundamental Foundations of Synthesis and Use of Advanced Materials” under the Priority program (for 2025-2036) (Youth and Children national project).