Silicon-based chain polymers

Have we ever thought about what is included in the enamels, varnishes for painting the fronts? What elements do anticorrosion coatings, resins, sealing gaskets contain? Certainly, we never take into consideration their composition. However, without all these products life on Earth would be a nightmare, i.e. different kinds of equipment would suffer a lack of leak tight integrity, not to mention that there would not be a variety of liquids, glues and resins used almost everywhere. Houses would collapse; cars, planes and other vehicles would have to be constantly repaired; we would not have silicon hand creams that protect housewives from harmful detergents. Unbelievably, but it is all about polymers based on silicon.

Silicon-based chain polymers Unsplash License

This essay provides an overview on the fields of their current and prospective application: from huge metallurgical industry, chemical engineering, metal processing to agriculture and medicine.

Let me start with the definition of silicon-based chain polymers. They are high-molecular compounds containing silicon and carbon atoms in the elemental unit of a macromolecule. The most important in the industry are polyorganosiloxanes (polysiloxanes), the main molecular chain of which consists of alternating silicon and oxygen atoms. Depending on the molecular weight, organosilicon polymers are viscous colorless liquids, solid elastic substances or fragile products. The development of chemistry of organosilicon compounds is predominantly based on our domestic science.

The study of silicon-based chain polymers

The study of silicon compounds was conducted by Russian chemists N.I. Lavrov, G.G. Gustavson, and N.N. Beketov. Especially valuable are the studies of P.P. Shorygin and N.E. Khotinsky, devoted to the synthesis of organosilicon compounds. As far as the works of the Soviet, scientists are concerned, Professor B.N. Dolgov’s research is of great interest. In 1933, he published his first monograph on organosilicon compounds, in which he predicted the possibility of their wide practical application. In light of the evidence from Academician Andrianov’s study on high-molecular organosilicon compounds (1937), we have a better understanding of synthesising silicon resins and the production of organosilicon polymers. In addition, the first organosilicon compound, which is in demand now, was discovered by the French chemist J. Ebelman in 1845. By the interaction of silicon tetrachloride and ethyl alcohol, he obtained ethyl orthosilicic acid (tetraethoxysilane, ethyl silicate) [1]. Then four-substituted organic silicon compounds and other bonds were also studied. It should be noted that these discoveries led to great interest in organoelement compounds of this class. At present, several thousand organosilicon compounds have been synthesised, their physico-chemical properties, methods of synthesis, and the field of their practical application have been under study.

Third, silicon fluids are good electrical insulating materials; they are transparent and have hydrophobic properties [2]. Such a rare combination of properties makes it possible to use them in additives for motor oils, for the production of various lubricants, liquids used at low and high temperatures, in cosmetics, paint coatings, for engraining clothes and upholstery fabrics, polishes, medical equipment and so on. Furthermore, organosilicon polymers have good compressibility, which allows engineers to use them in liquid shock absorbers of aircraft undercarts. Since most organic materials do not adhere to organosilicon polymers, organosilicon fluids are often used in the form of films to facilitate the separation of the product from the mold, for instance, when molding rubber and plastics or casting metals under pressure. Coupled with thermal and water resistance of organosilicon liquids, their excellent electrical insulating properties and resistance to breakdown in electrical fields makes it possible to use them in the insulation of aircraft engine candles, in radio and X-ray equipment, antennas, switches, ignition systems of marine engines, batteries, and electric cables. The liquids have also found wide application in processing textiles. These fabrics look exquisite and are pleasant to touch; besides they possess water-repellent properties. These benefits are extremely valuable for clothing and upholstery fabrics.

Experiments in a chemistry lab

It cannot be denied that silicon-based polymers are widely used particularly in each sphere of our everyday life. I suppose it is due to their physical properties and chemical characteristics. First of all, organosilicon polymeric liquids are odorless, heat-resistant, they do not burn and are hardly exposed to water and most chemical and physical exposure. Second, they have little impact on most of the organic materials such as plastics, rubbers, paints or living tissues and organisms.

Another key thing to remember is the importance of silicon resins in contemporary manufacturing. Exceptional hydrophobicity, heat resistance and other qualities have allowed to increase the reliability of machines and equipment, reduce their weight and contributed to the creation of up-to-date electrical insulators, protective coatings, etc. You can see more

In my view, elastoplastic is also of great significance in manufacturing. Organosilicon polymers with high molecular weights are cross-linked among their molecules, resulting in the formation of silicon rubber. Then further vulcanization leads to producing elastoplastic that is almost indistinguishable from natural rubber. Depending on the degree of cross-linking, you can change the properties of the materials. For example, it is known that silicone rubber is nonrigid if stretched. It can be molded into sheets, pipes or other complex shapes. Not only are they resistant to ageing, but they cannot be destroyed by acids, alkalis, salts and oils either. It is clear that such properties of polyorganosilicon elastoplastic are essential for a number of purposes.

Human characters working in science laboratory

It goes without saying that the most important field of application of silicon-based polymers is its use in medicine. Silicons are widely used for surface treatment of various materials, especially glass equipment. Notably, the protective silicon films on the glass are used in blood transfusion: on such a surface the blood does not coagulate for several hours. The hydrophobization of laboratory glass with the help of organosilicon compounds also plays an integral part in clinical, biochemical and pharmaceutical laboratories. Thanks to their heat and oxidation resistance, methylphenyl silicon fluids are applicable for sterilising surgical instruments. What’s more, testing organosilicon fluids on animals and humans has proved that they are harmless. Therefore, organosilicon fluids have been used to prepare creams, ointments and other cosmetics. Silicon-based liquid polymers do not dry the skin and penetrate it faster than oils without leaving stains on its surface. Different kinds of ointments treat certain skin diseases and singes. It is remarkable that there is some possibility to use organosilicon liquids as solvents for intramuscular infusion drugs.

The scientists of the Siberian Branch of the Institute of Organic Chemistry have created a great number of new organic silicone compounds (drugs, pesticides, etc.). Agricultural pesticides possess high physiological activity. The effect of such drugs is amazing and yet unexplained. It can sound unbelievable but the animals that are experiencing clinical death can quickly recover to life with just a small amount of such drugs.

Taking into account all the above mentioned, I can highlight that silicon-based chain polymers have a vast sphere of application in the form of organosilicon liquids, resins, and rubbers in chemistry, manufacturing, medicine and agriculture. Still, this overview illustrates the prospects of further research in the area of polymers. The main obstacle to the mass distribution of silicons is their relatively high cost because of complex production technology. Although silicons have ceased to be considered a luxury after the large-scale industrial production, their exclusive properties can be used where other materials give much worse results. So, the main goal of researchers and industrial engineers is that they should work on increasing chemical yield and simplifying the production process of silicon-based polymers.

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