[Chemistry Class Notes] on Polymer Pdf for Exam

A polymer is defined as any of a class of synthetic or natural substances which is composed of very large molecules, that are called macromolecules, which are the multiples of simpler chemical units-monomers. Polymers make up several materials in the living organisms. For example, cellulose, nucleic acids, and proteins. However, they constitute the basis of such minerals as quartz, feldspar, and diamond and such man-made materials as glass, concrete, plastics, rubber, and paper.

More About Polymer

The term polymer designates an unspecified monomer unit count. When the monomers count is very large, sometimes, the compound is known as a high polymer. Polymers are not restricted to the monomers of similar molecular weight and structure or chemical composition. A few natural polymers are composed of a kind of monomer. However, most synthetic and natural polymers are made up of either two or more different types of monomers, and such polymers are called copolymers.

Organic Polymers

Organic polymers play a vital role in living things by providing basic structural materials and participating in the processes of vital life. For example, the solid parts of all the plants are prepared by polymers. These include lignin, cellulose, and various resins. Cellulose is a type of polysaccharide, which is a polymer, composed of sugar molecules. Lignin contains a three-dimensional complicated polymer network. Wood resins are the polymers of simple isoprene, a hydrocarbon. Rubber is another familiar isoprene polymer.

Some Important Natural Polymers

Some other important natural polymers are given as proteins, which are the polymers nucleic acids and amino acids, which are the polymers of nucleotides.  These complex molecules are composed of nitrogen-containing bases, phosphoric acids, and sugars. In the cell, nucleic acids carry genetic information. Starches, which are the important sources of food energy derived from plants, are the natural polymers, composed of glucose.

Inorganic Polymers

Most of the inorganic polymers are found in nature, including diamond, graphite, where these both are composed of carbon. In diamond, the carbon atoms are linked in a three-dimensional network, which gives the hardness of the material. Whereas in graphite, it is used as a lubricant and in pencil “leads,” the carbon atoms link in planes that slide across the other.

Synthetic Polymers

These polymers are produced in various types of reactions. Most of the simple hydrocarbons, like propylene and ethylene, are transformed into polymers by adding one monomer after the other to the growing chain. Polyethylene is composed of repeating ethylene monomers and is an additional polymer. It can contain as many as 10,000 monomers joined in a long coiled chain. Polyethylene is translucent, thermoplastic, and crystalline. It means it softens when heated.

It is also used for packaging, coatings, moulded parts, and in the manufacturing of containers and bottles. Polypropylene is thermoplastic and crystalline, but it is harder compared to polyethylene. Its molecules can consist from 50,000 to 200,000 monomers. This is the compound, used in the textile industry and in making moulded objects.

Other Important Polymers

Other additional polymers include polyisoprene, polychloroprene, polybutadiene, which are all essential in manufacturing synthetic rubbers. A few polymers, like polystyrene, are transparent and glassy at room temperature and are thermoplastic as well. Polystyrene can be coloured any shade, and it can be used in the manufacture of toys and some other plastic objects.

If a single hydrogen atom in ethylene is replaced with a chlorine atom, it produces a vinyl chloride. This polymerizes to polyvinyl chloride (which is PVC), a hard, colourless, tough, thermoplastic material that is manufactured in a number of forms, including films, fibres, and foams. Vinyl acetate, which is produced by the ethylene and acetic acid reaction, polymerizes to amorphous, soft resins can be used as adhesives and coatings. It copolymerized with vinyl chloride to form a large family of thermoplastic materials.

Most of the important polymers contain nitrogen or oxygen atoms, along with the carbon, in the backbone chain. Among that macromolecular material with oxygen atoms are given as polyacetals. Polyformaldehyde is the simplest polyacetal, and it holds a high melting point and is crystalline and abrasion and also resistant to the action of solvents. Acetal resins are mostly the same metal as are many other plastics and they are used in machine parts manufacturing such as bearings and gears.

A linear polymer, which is characterized by an ester group repetition along with the backbone chain, is known as polyester. The open-chain polyesters are crystalline, colourless, and thermoplastic materials. Those with higher molecular weights (from 10,000 to 15,000 molecules) are employed in the manufacturing of moulded objects, films, and fibres like Dacron.

These polyamides include the naturally occurring proteins casein, which is found in milk, and zein, found in corn (which is also called maize), from which fibres, plastics, coatings, and adhesives are made. Among the synthetic polyamides, urea-formaldehyde resins are thermosetting. They can be used to form moulded objects and as coatings and adhesives for paper and textiles. Also, nylons are the important polyamide resins. They are strong and resistant to abrasion and heat, nontoxic, and noncombustible, and they can be coloured. Textile fibres are their best-known use, but they have several other applications.