Organoelement, organic and inorganic polymers exist in nature. Inorganic materials are those whose main chain is inorganic and the side branches are not hydrocarbon radicals. Elements of III-VI groups of the periodic system of chemical elements are most prone to the formation of polymers of inorganic origin.
Classification
Organic and inorganic polymers are actively studied, their new characteristics are determined, therefore, a clear classification of these materials has not yet been developed. However, certain groups of polymers can be distinguished.
Depending on the structure:
- linear
- flat;
- branched;
- polymer nets;
- three-dimensional and others.
Depending on the atoms of the main chain forming the polymer:
- homo-chain type (-M-) n - consist of one type of atom;
- hetero-chain type (-ML-) n - consist of various types of atoms.
Depending on origin:
For assignment to inorganic polymers of substances that in the solid state are macromolecules, it is also necessary that they have a certain anisotropy of the spatial structure and corresponding properties.
Main characteristics
Heterose polymers are more common, in which alternation of electropositive and electronegative atoms, for example B and N, P and N, Si and O, takes place. Heterochain inorganic polymers (NPs) can be obtained using polycondensation reactions. The polycondensation of oxoanions is accelerated in an acidic environment, and the polycondensation of hydrated cations in an alkaline environment. Polycondensation can be carried out both in solution and in solids in the presence of high temperature.
Many of hetero-chain inorganic polymers can only be obtained under conditions of high-temperature synthesis, for example, directly from simple substances. The formation of carbides, which are polymer bodies, occurs during the interaction of some oxides with carbon, as well as in the presence of high temperature.
Long homo chain chains (with a degree of polymerization n> 100) form carbon and p-elements of group VI: sulfur, selenium, tellurium.
Inorganic Polymers: Examples and Applications
The specificity of NPs is the formation of polymer crystalline bodies with a regular three-dimensional structure of macromolecules. The presence of a rigid framework of chemical bonds provides such compounds with significant hardness.
The specified property allows the use of inorganic polymers as abrasive materials . The use of these materials has found widespread application in industry.
The exceptional chemical and thermal resistance of the NP is also a valuable property. For example, reinforcing fibers made from organic polymers are stable in air to a temperature of 150-220 ° C. Meanwhile, boron fiber and its derivatives remain stable up to a temperature of 650 ° C. That is why inorganic polymers are promising for the creation of new chemically and heat-resistant materials.
NP are also of practical importance, which are at the same time approximating organic properties and preserving their specific properties. These include phosphates, polyphosphazenes, silicates, polymer sulfur oxides with various side groups.
Carbon polymers
The task: “Give examples of inorganic polymers,” is often found in chemistry textbooks. It is advisable to carry it out with reference to the most prominent NP - carbon derivatives. After all, this includes materials with unique characteristics: diamonds, graphite and carbine.
Carbin is an artificially created, poorly studied linear polymer with unsurpassed strength indicators, not inferior, but according to a number of studies and superior to graphene. However, carbine is a mysterious substance. After all, not all scientists recognize its existence as an independent material.
Outwardly, it looks like a metal-crystalline black powder. It has semiconductor properties. The electrical conductivity of carbine increases significantly under the influence of light. It does not lose these properties even at temperatures up to 5000 ° C, which is much higher than for other materials of this purpose. Received material in the 60s V.V. Korshakom, A.M. Sladkov, V.I. Kasatotkin and Yu.P. Kudryavtsev by catalytic oxidation of acetylene. The most difficult thing was to determine the type of bonds between carbon atoms. Subsequently, a substance with only double bonds between carbon atoms was obtained at the Institute of Organoelement Compounds of the USSR Academy of Sciences. The new compound was called polycumulene.
Graphite - in this material, polymer ordering spreads only in the plane. Its layers are connected not by chemical bonds, but by weak intermolecular interactions, so it conducts heat and current and does not transmit light. Graphite and its derivatives are fairly common inorganic polymers. Examples of their use: from pencils to the nuclear industry. By oxidizing graphite, intermediate oxidation products can be obtained.
Diamond - its properties are fundamentally different. Diamond is a spatial (three-dimensional) polymer. All carbon atoms are bonded together by strong covalent bonds. Because this polymer is extremely durable. Diamond does not conduct current and heat, has a transparent structure.
Boron Polymers
If you are asked about what inorganic polymers are known to you, feel free to answer - boron polymers (-BR-). This is a fairly extensive class of NP, widely used in industry and science.
Boron carbide - its formula more correctly looks like (B12C3) n. Its unit cell is rhombohedral. The framework is formed by twelve covalently bound boron atoms. And in the middle of it is a linear group of three covalently bonded carbon atoms. The result is a very robust construction.
Borides - their crystals are formed like the carbide described above. The most resistant of them is HfB2, which melts only at a temperature of 3250 ° C. TaB2 is noted for the highest chemical resistance - neither acids nor their mixtures act on it.
Boron nitride - it is often called white talcum powder for similarities. This similarity is really only external. Structurally, it is similar to graphite. Get it by heating boron or its oxide in an atmosphere of ammonia.
Borazon
Elbor, borazon, kiborite, kingsongite, cubonite are superhard inorganic polymers. Examples of their application: the manufacture of grinding wheels, abrasive materials, metal processing. These are chemically inert substances based on boron. In hardness, it is closer to diamonds than other materials. In particular, borazon leaves scratches on the diamond, the latter also leaves scratches on the crystals of borazon.
However, these NPs have several advantages over natural diamonds: they have high heat resistance (they can withstand temperatures up to 2000 ° C, diamond breaks at temperatures in the range of 700-800 ° C) and high resistance to mechanical stress (they are not so fragile). Borazon was obtained at a temperature of 1350 ° C and a pressure of 62,000 atmospheres by Robert Ventorf in 1957. Similar materials were obtained by Leningrad scientists in 1963.
Inorganic Sulfur Polymers
Homopolymer - this modification of sulfur has a linear molecule. The substance is not stable; upon fluctuations in temperature it decomposes into octahedral cycles. Formed in the case of a sharp cooling of the sulfur melt.
Polymer modification of sulfur dioxide. Very similar to asbestos, has a fibrous structure.
Selenium Polymers
Gray selenium is a polymer with spiral linear macromolecules embedded in parallel. In chains, selenium atoms are covalently bonded, and macromolecules are linked by molecular bonds. Even molten or dissolved selenium does not decompose into individual atoms.
Red or amorphous selenium is also a polymer of a chain but disordered structure. In the temperature range of 70-90 ° C, it acquires rubber-like properties, turning into a highly elastic state, which reminds organic polymers.
Selenium carbide, or rhinestone. Thermally and chemically stable, sufficiently strong spatial crystal. Piezoelectric and semiconductor. Under artificial conditions, it was obtained by the reaction of quartz sand and coal in an electric furnace at a temperature of about 2000 ° C.
Other polymers of selenium:
- Monoclinic selenium is more ordered than amorphous red, but inferior to gray.
- Selenium dioxide, or (SiO2) n - is a three-dimensional network polymer.
- Asbestos is a polymer of selenium oxide of a fibrous structure.
Phosphorus polymers
There are many modifications of phosphorus: white, red, black, brown, purple. Red - NP fine crystalline structure. It is obtained by heating white phosphorus without air at a temperature of 2500 ° C. Black phosphorus was obtained by P. Bridgman under the following conditions: pressure of 200,000 atmospheres at a temperature of 200 ° C.
Phosphoronitride chlorides are compounds of phosphorus with nitrogen and chlorine. The properties of these substances change with increasing mass. Namely, their solubility in organic substances decreases. When the molecular weight of the polymer reaches several thousand units, a rubbery substance is formed. This is the only sufficiently heat-resistant carbon-free rubber. It only breaks down at temperatures above 350 ° C.
Conclusion
Inorganic polymers are mostly substances with unique characteristics. They are used in production, in construction, for the development of innovative and even revolutionary materials. As you study the properties of known NPs and create new ones, their scope expands.