Natural polymer - formula and application

Most of the modern building materials, medicines, fabrics, household items, packaging and consumables are polymers. This is a whole group of compounds with characteristic distinguishing features. There are a lot of them, but despite this, the number of polymers continues to grow. Indeed, synthetic chemists annually discover more and more new substances. At the same time, natural polymer was of particular importance at all times. What are these amazing molecules? What are their properties and what are the features? We will answer these questions during the article.

Polymers: General Description

From the point of view of chemistry, a polymer is considered to be a molecule having a huge molecular weight: from several thousand to millions of units. However, in addition to this feature, there are several more by which substances can be classified precisely as natural and synthetic polymers. It:

• constantly repeating monomer units that are connected through different interactions;
• the degree of polymerase (i.e. the number of monomers) must be very high, otherwise the compound will be considered an oligomer;
• specific spatial orientation of the macromolecule;
• a set of important physico-chemical properties that are characteristic only for this group.

In general, a substance of polymer nature is quite easy to distinguish from others. One has only to look at his formula to understand this. A typical example is the well-known polyethylene widely used in everyday life and industry. It is the product of a polymerization reaction in which the unsaturated hydrocarbon ethene or ethylene enters. The reaction in general is written as follows:

nCH ₂ = CH ₂ → (-CH-CH-) _n , where n is the degree of polymerisation of the molecules, showing how many monomer units are in its composition.

Also, as an example, you can cite a natural polymer, which is well known to everyone, this is starch. In addition, amylopectin, cellulose, chicken protein and many other substances belong to this group of compounds.

The reactions that can result in macromolecules can be of two types:

• polymerization;
• polycondensation.

The difference is that in the second case, the interaction products are low molecular weight. The structure of the polymer can be different, it depends on the atoms that form it. Often there are linear forms, but there are three-dimensional mesh, very complex.

If we talk about the forces and interactions that hold the monomer units together, then we can outline several main ones:

• Van der Waals forces;
• chemical bonds (covalent, ionic);
• Electrostatic interaction.

All polymers cannot be combined into one category, since they have a completely different nature, the method of formation, and perform different functions. Their properties also vary. Therefore, there is a classification that allows us to divide all the representatives of this group of substances into different categories. It can be based on several features.

Polymer Classification

If we take as a basis the qualitative composition of the molecules, then all the substances under consideration can be defined in three groups.

1. Organic - these are those that include carbon, hydrogen, sulfur, oxygen, phosphorus, nitrogen atoms. That is, those elements that are biogenic. Examples can be given a lot: polyethylene, polyvinyl chloride, polypropylene, rayon, nylon, natural polymer - protein, nucleic acids and so on.
2. Organoelemental - those whose composition includes some extraneous inorganic and non- nutrient element. Most often it is silicon, aluminum or titanium. Examples of such macromolecules: organic glass, fiberglass, composite materials.
3. Inorganic - the chain is based on silicon atoms, not carbon. Radicals can also be part of the side branches. They were discovered recently, in the middle of the 20th century. Used in medicine, construction, technology and other industries. Examples: silicone, cinnabar.

If the polymers are separated by origin, then three groups can be distinguished.

1. Natural polymers that have been widely used since antiquity. These are macromolecules for the creation of which man did not exert any efforts. They are the products of reactions of nature itself. Examples: silk, wool, protein, nucleic acids, starch, cellulose, leather, cotton and others.
2. Artificial. These are macromolecules that are created by man, but based on natural analogues. That is, the properties of an existing natural polymer are simply improved and changed. Examples: artificial rubber, rubber.
3. Synthetic - these are polymers in the creation of which only people participate. There are no natural analogues for them. Scientists are developing methods for the synthesis of new materials that are distinguished by improved technical characteristics. This is how synthetic polymeric compounds of various kinds are born. Examples: polyethylene, polypropylene, viscose, acetate fiber and so on.

There is another sign that underlies the separation of the substances in question into groups. This is reactivity and thermal stability. Two categories are distinguished by this parameter:

• thermoplastic;
• thermosetting.

The most ancient, important and especially valuable is still a natural polymer. Its properties are unique. Therefore, we will consider this category of macromolecules further.

Which substance is a natural polymer?

To answer this question, first look around you. What surrounds us? The living organisms around us that feed, breathe, multiply, bloom and produce fruits and seeds. And what are they from a molecular point of view? These are compounds such as:

• proteins;
• nucleic acids;
• polysaccharides.

So, each of these compounds is a natural polymer. Thus, it turns out that life around us exists only due to the presence of these molecules. Since ancient times, people have used clay, building mixtures and mortars to strengthen and create homes, woven yarn from wool, used cotton, silk, wool and animal skin to create clothes. Natural organic polymers accompanied man at all stages of his formation and development and in many ways helped him achieve the results that we have today.

Nature itself gave everything so that people's life was as comfortable as possible. Over time, rubber was discovered, its remarkable properties were clarified. Man learned to use starch for food purposes, and cellulose for technical purposes. Camphor, which is also known since ancient times, is a natural polymer. Resins, proteins, nucleic acids are all examples of the compounds in question.

The structure of natural polymers

Not all representatives of this class of substances are arranged in the same way. So, natural and synthetic polymers can vary significantly. Their molecules are oriented in such a way as to be as profitable and convenient as possible from an energy point of view. Moreover, many natural species are able to swell and their structure changes in the process. There are several most common options for the structure of the chain:

• linear
• branched;
• stellate;
• flat;
• mesh;
• tape
• comb-like.

Artificial and synthetic representatives of macromolecules have a very large mass, a huge number of atoms. They are created with specially defined properties. Therefore, their structure was originally planned by man. Natural polymers are most often either linear or mesh in structure.

Examples of natural macromolecules

Natural and artificial polymers are very close to each other. After all, the former become the basis for the creation of the latter. There are many examples of such transformations. Here are some of them.

1. Plain milky white plastic is a product obtained by treating cellulose with nitric acid with the addition of natural camphor. The polymerization reaction leads to the solidification of the obtained polymer and transformation into the desired product. A plasticizer - camphor, makes it able to soften when heated and change its shape.
2. Acetate silk, copper-ammonia fiber, viscose - all these are examples of those threads, fibers that are obtained on the basis of cellulose. Fabrics made from natural cotton and linen are not so strong, not shiny, easily wrinkled. But the artificial analogues of their these shortcomings are devoid, which makes their use very attractive.
3. Artificial stones, building materials, mixtures, leather substitutes are also examples of polymers derived from natural raw materials.

The substance, which is a natural polymer, can be used in its true form. There are many such examples too:

• rosin;
• amber;
• starch;
• amylopectin;
• cellulose;
• fur;
• wool;
• cotton;
• silk;
• cement;
• clay;
• lime;
• proteins;
• nucleic acids and so on.

Obviously, the class of compounds considered by us is very numerous, practically important and significant for people. Now let us consider in more detail several representatives of natural polymers, which are very popular at the present time.

Silk and wool

The formula of the natural silk polymer is complex, because its chemical composition is expressed by the following components:

• fibroin;
• sericin;
• waxes;
• fats.

The main protein itself is fibroin, which includes several varieties of amino acids. If you imagine its polypeptide chain, it will look something like this: (-NH-CH ₂ -CO-NH-CH (CH ₃ ) -CO-NH-CH ₂ -CO-) _n. And this is only part of it. If we imagine that a no less complex molecule of sericin protein is attached to this structure with the help of Van der Waals forces, together they are mixed into a single conformation with wax and fats, then it is clear why it is difficult to depict the formula of natural silk.

Today, most of this product is supplied by China, because in its open spaces there is a natural habitat for the main producer - silkworm. Previously, from the most ancient times, natural silk was very appreciated. Only noble, wealthy people could afford clothes from it. Today, many of the characteristics of this fabric leave much to be desired. For example, it is strongly magnetized and wrinkled, in addition, from exposure to the sun it loses its luster and fades. Therefore, artificial derivatives based on it are more in use.

Wool is also a natural polymer, since it is a vital product of the skin and sebaceous glands of animals. On the basis of this protein product, knitwear is made, which, like silk, is a valuable material.

Starch

The natural polymer starch is a plant product. They produce it as a result of the photosynthesis process and accumulate in different parts of the body. Its chemical composition:

• amylopectin;
• amylose;
• alpha glucose.

The spatial structure of starch is very branched, disordered. Thanks to amylopectin, which is part of it, it is able to swell in water, turning into the so-called paste. This colloidal solution is used in engineering and industry. Medicine, the food industry, the manufacture of wallpaper adhesives are also areas of use of this substance.

Among the plants containing the maximum amount of starch, we can distinguish:

• corn;
• potatoes;
• rice
• wheat
• cassava;
• oats;
• buckwheat;
• bananas
• sorghum.

On the basis of this biopolymer, bread is baked, pasta is made, jelly, cereals and other food products are cooked.

Cellulose

From the point of view of chemistry, this substance is a polymer whose composition is expressed by the formula (C ₆ H ₅ O ₅ ) _n . The monomer link in the chain is beta glucose. The main places of cellulose content are plant cell walls. That is why wood is a valuable source of this compound.

Cellulose is a natural polymer that has a linear spatial structure. It is used for the production of the following types of products:

• pulp and paper products;
• faux fur;
• different types of artificial fibers;
• cotton
• plastics
• smokeless gunpowder;
• films and so on.

Obviously, its industrial significance is great. So that this compound can be used in production, it should first be extracted from plants. This is done by long cooking wood in special devices. Further processing, as well as the reagents used for digestion, vary. There are several ways:

• sulfite;
• nitrate;
• soda;
• sulfate.

After similar processing, the product still contains impurities. It is based on lignin and hemicellulose. To get rid of them, the mass is treated with chlorine or alkali.

In the human body there are no such biological catalysts that would be able to split this complex biopolymer. However, some animals (herbivores) have adapted to this. In their stomach certain bacteria settle that do it for them. In return, microorganisms receive energy for life and habitat. This form of symbiosis is extremely beneficial for both parties.

Rubber

This is a natural polymer with valuable economic value. It was first described by Robert Cook, who discovered one of his travels. It happened so. Having landed on the island on which the natives unknown to him lived, he was hospitably greeted by them. His attention was attracted by local children who played an unusual subject. This spherical body pushed off the floor and bounced high up, then returned.

Inquiring from the local population about what this toy is made of, Cook found out that the juice of one of the trees - hevea - freezes. Much later it was found out that this is a rubber biopolymer.

The chemical nature of this compound is known - it is isoprene, which underwent natural polymerization. Rubber formula (C ₅ H ₈ ) _n . Its properties, due to which it is so highly regarded, are as follows:

• elasticity;
• wear resistance;
• electrical insulation;
• water resistant.

However, there are also disadvantages. In the cold, it becomes brittle and brittle, and in the heat it becomes sticky and malleable. That is why there was a need for the synthesis of analogues of artificial or synthetic bases. Today rubbers are widely used for technical and industrial purposes. The most important products based on them:

• rubber;
• ebonites.

Amber

It is a natural polymer, because in its structure it is a resin, its fossil form. The spatial structure is an amorphous framework polymer. Very flammable, you can light it with the flame of a match. It has luminescence properties. This is a very important and valuable quality that is used in jewelry. Amber-based jewelry is very beautiful and in demand.

In addition, this biopolymer is used for medical purposes. Sandpaper and varnish coatings for various surfaces are made from it.