Natural polymer - formula and application

Most of the modern building materials, medicines, tissues, household items, packaging and consumables are polymers. This is a whole group of compounds that have distinctive characteristics. There are a lot of them, but despite this, the number of polymers continues to grow. After all, synthetic chemists discover more and more new substances every year. At the same time, it was natural polymer that had a special significance at all times. What are these amazing molecules? What are their properties and what are the features? We will answer these questions in the course of the article.

Polymers: general characteristics

From the point of view of chemistry, it is customary to consider a polymer having a huge molecular mass: from several thousand to millions of units. However, in addition to this feature, there are several more, according to which substances can be classified exactly as natural and synthetic polymers. It:

• Constantly repeating monomeric links, which are connected by means of different interactions;
• The degree of polymerization (that is, the number of monomers) must be very high, otherwise the compound will be considered an oligomer;
• Definite spatial orientation of the macromolecule;
• A set of important physico-chemical properties, characteristic only for this group.

In general, the substance of the polymeric nature is quite easy to distinguish from the 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 into which an unsaturated hydrocarbon of ethene or ethylene enters. The reaction in general form is written as follows:

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

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

Reactions, as a result of which macromolecules can form, are of two types:

• Polymerization;
• Polycondensation.

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

If we talk about the forces and interactions that hold the monomeric links together, then we can identify a few basic ones:

• Van der Waals forces;
• Chemical bonds (covalent, ionic);
• Electronostatic interaction.

All polymers can not be combined into one category, since they have a completely different nature, a mode of formation, and perform unequal functions. Their properties also vary. Therefore, there is a classification that allows all representatives of this group of substances to be divided into different categories. It can be based on several signs.

Classification of polymers

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

1. Organic - these are those that include atoms of carbon, hydrogen, sulfur, oxygen, phosphorus, nitrogen. That is, those elements that are biogenic. Examples include mass: polyethylene, polyvinyl chloride, polypropylene, viscose, nylon, natural polymer - protein, nucleic acids and so on.
2. Elementorganichnye - such, which include some extraneous inorganic and non- biogenic element. Most often it is silicon, aluminum or titanium. Examples of such macromolecules are: organic glass, glass polymers, composite materials.
3. Inorganic - at the heart of the chain are silicon atoms, not carbon. Radicals can also be part of lateral branches. They were discovered very recently, in the middle of the 20th century. Used in medicine, construction, engineering and other industries. Examples: silicone, cinnabar.

If we divide polymers by their origin, we can distinguish three groups of them.

1. Natural polymers, the use of which has been widely implemented since ancient times. These are such macromolecules, for the creation of which the man made no effort. They are products of the reactions of nature itself. Examples: silk, wool, protein, nucleic acids, starch, cellulose, leather, cotton and others.
2. Artificial. These are such macromolecules that are created by man, but on the basis of natural analogues. That is, the properties of an already existing natural polymer simply improve and change. Examples: artificial rubber, rubber.
3. Synthetic - these are polymers, in the creation of which only a person participates. There are no natural counterparts for them. Scientists are developing methods for the synthesis of new materials, which would be distinguished by improved technical characteristics. So synthetic polymeric compounds of various kinds are born. Examples: polyethylene, polypropylene, viscose, acetate fiber and the like.

There is one more feature that underlies the separation of the substances under consideration into groups. This is the reactivity and thermal stability. There are two categories in 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.

Which substance is a natural polymer?

To answer this question, first look around you. What surrounds us? Living organisms around us that feed, breathe, reproduce, bloom and give fruits and seeds. And what are they from the molecular point of view? These are such connections as:

• Proteins;
• nucleic acids;
• Polysaccharides.

So, the natural polymer is each of the above compounds. Thus, it turns out that life around us exists only because of the presence of these molecules. From the earliest times, people used clay, mortar and mortar to strengthen and create a home, woven yarn from wool, used cotton, silk, wool and animal skin to create clothing. Natural organic polymers accompanied the person 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 to ensure that people's lives were as comfortable as possible. Over time, rubber was discovered, its remarkable properties were clarified. Man learned to use starch for food purposes, in technical - cellulose. The natural polymer is also camphor, which is also known from ancient times. Resins, proteins, nucleic acids are all examples of the compounds under consideration.

Structure of natural polymers

Not all representatives of this class of substances are arranged identically. Thus, natural and synthetic polymers can vary significantly. Their molecules are oriented so that it is most profitable and convenient to exist from the energy point of view. At the same time, many natural species are capable of swelling and their structure changes in the process. There are several most common variants of the chain structure:

• Linear;
• Branched;
• Stellate;
• Flat;
• Mesh;
• Tape;
• Comb-shaped.

Artificial and synthetic representatives of macromolecules have a very large mass, a huge number of atoms. They are created with specially assigned properties. Therefore, their structure is originally planned by man. Natural polymers are 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. Examples of such transformations are many. Here are some of them.

1. Conventional milk-white plastic is a product obtained by processing nitric acid of cellulose with the addition of natural camphor. The polymerization reaction results in the solidification of the resulting polymer and conversion to the desired product. A plasticizer - camphor, makes it able to soften when heated and change its shape.
2. Acetate silk, copper-ammonia fiber, viscose are all examples of those yarns, fibers that are produced on the basis of cellulose. Fabrics made from natural cotton and linen are not as strong, not shiny, easily crumpled. But artificial analogues of their shortcomings are deprived, which makes their use very attractive.
3. Artificial stones, building materials, mixtures, leatherette are also examples of polymers obtained on the basis of natural raw materials.

A substance that is a natural polymer can be used in its true form. There are many such examples:

• rosin;
• amber;
• starch;
• Amylopectin;
• cellulose;
• fur;
• wool;
• cotton;
• silk;
• cement;
• clay;
• lime;
• Proteins;
• Nucleic acids and so on.

Obviously, the class of compounds we are considering is very numerous, practically important and meaningful for people. Now consider in more detail several representatives of natural polymers, which are very in demand at the moment.

Silk and wool

The formula of 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, it includes several varieties of amino acids. If we represent 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 an equally complex molecule of sericin protein joins this structure with the help of van der Waals forces, they combine together into a single conformation with wax and fats, then it is understandable why it is difficult to depict the formula of natural silk.

To date, most of this product is supplied by China, because on its expanses there is a natural habitat of the main producer - silkworm. Previously, since the most ancient times, natural silk was very appreciated. Only noble, rich people could afford clothes from him. Today many characteristics of this fabric leave much to be desired. For example, it strongly magnetizes and crumples, in addition, from being in the sun loses its shine and dims. Therefore, more in the use of artificial derivatives based on it.

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

Starch

Natural polymer starch is a product of plant life. They produce it as a result of the process of photosynthesis 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 the amylopectin included in the composition, it is able to swell in water, turning into a 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.

Based on this biopolymer bake bread, make pasta, boiled jelly, porridge and other food products.

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 monomeric link of the chain is beta-glucose. The main places of cellulose content are cell walls of plants. That is why wood is a valuable source of this connection.

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;
• Artificial fur;
• Different types of artificial fibers;
• Cotton;
• Plastics;
• Smokeless powder;
• Film and so on.

It is obvious that its industrial importance is great. In order for this compound to be used in production, it must first be extracted from plants. This is done by prolonged cooking of wood in special devices. Further processing, as well as the reagents used for digestion, are different. There are several ways:

• Sulfite;
• nitrate;
• Soda;
• Sulfate.

After such 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, which 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, which has a valuable economic value. It was first described by Robert Cook, who discovered it in one of his travels. It happened so. Landed on the island, on which the natives, unknown to him, lived, he was hospitably received by them. His attention was attracted by local children who played an unusual subject. This spherical body pushed away from the floor and jumped high up, then came back.

Asked the local population about what made this toy, Cook found out that the juice of one of the trees - Hevea - stiffens. Much later it was found out that this is the biopolymer rubber.

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

• elasticity;
• Wear resistance;
• Electrical insulation;
• Water resistance.

However, there are disadvantages. In the cold, it becomes brittle and brittle, and on the heat - sticky and sticky. That is why there was a need to synthesize analogues of an artificial or synthetic basis. 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 represents resin, its fossil form. The spatial structure is a framework amorphous polymer. Very combustible, you can light it with the flame of a match. Possesses luminescence properties. This is a very important and valuable quality, which is used in jewelry business. Jewelery based on amber is very beautiful and in demand.

In addition, this biopolymer is also used for medical purposes. It also produces sandpaper, varnish coatings for various surfaces.