In nature there are organometallic, organic and inorganic polymers.Refers to inorganic materials, wherein the inorganic backbone, and not laterals are hydrocarbon radicals.By forming polymers tend to most inorganic elements III-VI of the periodic system of chemical elements.
Classification
organic and inorganic polymers actively investigated, determined by their new features, so the precise classification of these materials have not yet worked out.However, it is possible to allocate certain groups of polymers.
Depending on the structure:
- linear;
- flat;
- branched;
- polymer networks;
- and other three-dimensional.
Depending on the atoms of the main chain constituting the polymer:
- gomotsepnye type (-M-) n - consist of one kind of atoms;
- hetero type (-ML-) n - are composed of different kinds of atoms.
Depending on the origin:
- natural;
- artificial.
For the assimilation of inorganic polymer materials which in the solid state are macromolecules, you also need the presence of a certain spatial anisotropy of the structure and the corresponding properties.
Main characteristics
More common are heterochain polymers, in which there is alternation electropositive and electronegative atoms such as B, N, P and N, Si and O. Get hetero inorganic polymers (NP) by using polycondensation reactions.Polycondensation oksoanionami accelerated in an acidic environment, and polycondensation hydrated cations - alkaline.Polycondensation can be carried out both in solution and in the solids in the presence of heat.
Many of hetero-inorganic polymers can be obtained only in a high-temperature synthesis, for example, directly from the simple substances.The formation of carbides, which are polymeric bodies occurs by reaction of some oxides with carbon, as well as in the presence of heat.
gomotsepnye Long chain (with a degree of polymerisation n & gt; 100) form a p-carbon and Group VI elements such as sulfur, selenium, tellurium.
inorganic polymers: examples and application
Specificity NP is the formation of polymeric crystalline solids with a regular three-dimensional structure of macromolecules.The presence of a hard skeleton of chemical bonds provides such compounds considerable hardness.
This property can be used as abrasives, inorganic polymers.The use of these materials has found wide application in industry.
exceptional chemical and thermal resistance of NP is also a valuable property.For example, the reinforcing fibers are made of organic polymers are stable in air to a temperature of 150-220? C.Meanwhile, boron fiber and its derivatives are stable up to a temperature of 650? C.That is why the inorganic polymers are promising for the creation of new chemical and heat-resistant materials.
also have practical significance of NP, which are both close in properties to organic, and retain their specific properties.These include phosphates, polyphosphazenes, silicates, polymeric sulfur oxides with different side groups.
polymers of carbon
task: "Give examples of inorganic polymers" - often found in chemistry textbooks.It is advisable to carry it out with a reference to the most prominent NP - derived carbon.After all, this includes materials with unique characteristics: diamond, graphite and carbyne.
Carbine - an artificially created, poorly studied linear polymer with unmatched strength, not to give in, and according to some studies, and superior graphene.However, carbine - a mysterious substance.Not all scientists acknowledge its existence as an independent material.
looks like a crystalline metal-black powder.It has semiconducting properties.Conductivity carbyne greatly increases under the action of light.It does not lose these properties even at temperatures up to 5000? C, which is much higher than for other materials such purpose.I get the material in the 60 VVKorshak, AMSladkov, VIKasatochkin and YPKudryavtsev by catalytic oxidation of acetylene.The hardest part was to determine the type of bonds between carbon atoms.Subsequently, the material was obtained only with double bonds between the carbon atoms at the Institute of Organoelement Compounds, USSR Academy of Sciences.The novel compound named polikumulen.
Graphite - in this polymer material ordering applies only in the plane.Its layers are not connected by chemical bonds and weak intermolecular interactions, so it conducts heat and current, and does not transmit light.Graphite and its derivatives - quite common inorganic polymers.Examples of their use: from the pencil to the nuclear industry.Oxidizing the graphite, it is possible to obtain intermediate products of oxidation.
Diamond - its properties are fundamentally different.Diamond is a spatial (three-dimensional) polymer.All of the carbon atoms are bonded together by strong covalent bonds.Because the polymer is extremely durable.Diamond does not conduct heat and has a transparent structure.
Polymers boron
If you are asked what you know of inorganic polymers, safely answer - polymers boron (-BR-).This is a rather large class of NP, widely used in industry and science.
Boron carbide - its correct formula looks like this (B12C3) n.His unit cell - rhombohedral.Frame form twelve covalently bonded boron atoms.In the middle of it - a linear group of three covalently bonded carbon atoms.The result is a very robust design.
Borides - their crystals are formed like the above carbide.Most of them are resistant HfB2, which melts only at a temperature of 3250 ° C.The greatest chemical stability observed TaB2 - it does not apply any acid or mixtures thereof.
Boron nitride - often called white talc for similarities.This is really only an external similarity.Structurally, it is similar to graphite.Receives it, or by heating the boron oxide in an ammonia atmosphere.
borazon
CBN Borazon, Kibora, kingsongit, CUBONE - superhard inorganic polymers.Examples of application: manufacture of grinding wheels, abrasives, metal processing.It is chemically inert substances based on boron.According to the hardness close to diamond other materials.In particular, borazon leave scratches on the diamond, the latter also leaves scratches on the crystal borazon.
However, the NP have several advantages over natural diamonds: they have a large temperature resistance (can withstand temperatures up to 2000 ° C, the diamond is degraded at rates in the range 700-800 ° C) and high resistance to mechanical stress (they are not as fragile).Borazon was obtained at 1350 ° C and a pressure of 62000 Wentorf atmospheres Robert 1957.Similar materials Leningrad scientists were obtained in 1963.
inorganic polymer sulfur
homopolymer - the modification of sulfur has a linear molecule.The substance is not stable, temperature fluctuations falls into octahedral cycles.Formed in the case of quenching molten sulfur.
Polymer modification of sulfur dioxide.Very similar to asbestos, it has a fibrous structure.
Polymers selenium
Grey selenium - a polymer with spiral linear macromolecules embedded in parallel.The chains of selenium atoms bound covalently bound macromolecules and molecular bonds.Even the molten or dissolved selenium does not break into separate atoms.
red amorphous selenium or a polymer chain, too, but malouporyadochennoy structure.In the temperature interval 70-90? C it gets rubbery properties, moving into high state resemblance to organic polymers.
Carbide selenium or rhinestone.Thermally and chemically stable, sufficiently strong spatial crystal.Piezoelectric and semiconductor.In vitro it obtained by reacting quartz sand and carbon in an electric furnace at a temperature of about 2000 ° C.
Other polymers selenium:
- Monoclinic selenium - more orderly than the amorphous red, but concedes gray.
- selenium dioxide, or (SiO2) n - is a three-dimensional crosslinked polymer.
- Asbestos - Selenium oxide polymer fiber structure.
Polymers phosphorus
There are many modifications of phosphorus: white, red, black, brown, purple.Red - NP fine crystalline structure.Prepared by heating white phosphorus without access to air at a temperature of 2500? C.Black phosphorus P. Bridgman obtained under the following conditions: pressure of 200,000 atmospheres at a temperature of 200 ° C.
Fosfornitridhloridy - phosphorus compounds with nitrogen and chlorine.The properties of these substances vary with increasing mass.Namely decreases their solubility in organic compounds.When the molecular weight of the polymer reaches several thousand units, formed rubber-like substance.It is only enough carbon-free heat-resistant rubber.It is destroyed only at temperatures above 350 ° C.
Conclusion
inorganic polymers in the majority - a substance with unique characteristics.They are used in manufacturing, construction, to develop innovative and even revolutionary materials.As the study of the properties of NP-known and new, their scope is expanding.
