Polymer
In nature there are huge molecules called macromolecules. These molecules are formed by hundreds of thousands of atoms so their molecular weights are very high. Polymers are a particular type of macromolecule, which is characterized by having a unit that repeats throughout the molecule. Small molecules that combine with each other through a process chemical, called polymerization reaction, to form the polymer it they call monomers. The union of all these small molecules gives rise to a structure of repetitive constitution in the polymer and the unit that repeats itself regularly throughout the entire molecule is known as the repetitive constitutional unit (ucr) or monomer unit.
The length of the polymer chain is determined by the number of ucr that are repeated in the chain. This is called the degree of polymerization (X), and its molecular weight is given by the weight of the repetitive constitutional unit multiplied by the degree of polymerization. In a certain polymer, if all the structural units are identical this is called homopolymer, but if it comes from two or more monomers it receives the name of copolymer.
For a substance to be considered a monomer, it must be have a functionality (f)> 2. The functionality is related to the number of functional groups present in the molecule, for example, acetic acid has a functionality of 1, while ethylenediamine has a functionality of two and glycerol has a functionality of three. In the case of olefins, the double bond is considered to have a functionality equal to 2. When the functionality of the monomer or monomers involved in a polymerization is 2 linear polymers are obtained, while if any of them has a higher functionality branched or crosslinked polymers are obtained.
The science of macromolecules studies both biological and synthetic materials. The group of biological polymers, which is related to the essence of life itself, is constituted among other substances by polysaccharides, such as starch and cellulose; proteins and nucleic acids.
Apart from these polymers that can be considered natural, they have been developed a quantity of synthetic polymers. Although the objective of the first syntheses was to obtain substitutes for some natural macromolecules such as rubber and silk, at present an impressive technology has been developed in this field, which dates back only a few decades, which produces hundreds of substances that do not have natural analogues and that are practically essential for the development of modern life.
Synthetic polymers can be classified into three different types of materials:
Elastomers
Substances that have the elasticity that characterizes rubber and like this are used to make rubber, hoses or tires.
Fibers
Materials able to be oriented to form long and thin filaments such as yarn. They have a great resistance along the axis of orientation, as it happens with cotton, wool and silk. They have their main application in the textile industry.
Plastics
They are polymers that can be molded under pressure and transformed into various objects with different shapes, or, used as paints or surface coatings.
Brief historical review of the polymers
Since ancient times, human beings have used polymers of natural origin to satisfy some of their needs. Asphalt was used in the Middle East in biblical times and cotton was known in Mexico before the arrival of Columbus. Also in pre-Columbus times the latex was known by some American peoples and the Mayans used it to make balls to play. Columbus and other explorers who visited this continent were fascinated with this material and brought samples of this material to Europe. Latex they found some applications, where the most important were made after the discovery of the vulcanization process. This discovery was achieved accidentally by the American Charles Goodyear in 1839 and gave rise to the rubber industry.
In the same nineteenth century there were other important discoveries such as that of nitrocellulose in 1846 by Christian Schönbein that was also accidentally achieved. In the same year, collodion was discovered, material from which celluloid was obtained in 1860 and which allowed the manufacture of combs and photographic films among other things. From the celluloid, the first billiard balls were manufactured in 1869, and in 1875 Alfred Nobel discovers the dynamite.
Already in the twentieth century, Leo Baekeland discovers in 1907 a resin thermostable prepared by reaction between phenol and formaldehyde which he named Bakelite inspired by his own name. The success of this researcher served as a stimulus to others in the search for new materials. However, by then the true nature of the polymers was not known and it was believed that these were molecular aggregates of many molecules small and their properties were attributed to various attractive forces that kept their components together. The concept of polymer, as we know it today, is due to Staudinger when in 1920 he introduced for the first time the idea of a macromolecular chain constituted by covalent bonds. In recognition of his work Staudinger received the Nobel Prize in 1953.
In the decade of the 30 thanks to the efforts of the chemist of the Du Pont Wallace Hume Carothers obtains the first synthetic fiber, a synthetic polyamide called Nylon. This discovery opened the way for the synthesis of many others. For its part, Bayer in Germany made significant advances in the field of polyurethanes. In those years, Teflon and poly methyl methacrylate were also discovered.
In 1955, thanks to the combined works of Karl Ziegler and Guilio Natta, a crystalline polypropylene was obtained and the concept of stereoregularity arose, which earned them the award of the Nobel Prize in 1955. Subsequently, the brilliant research of another outstanding scientist, Paul J. Flory, also He was awarded the Nobel Prize in 1974. Since then the development of new technologies, materials and applications of polymers has been explosive.
Summarizing the current applications of polymers is an almost impossible task. In the contemporary world, synthetic polymers have covered all areas of development and manufacturing of manufactured products, replacing traditionally used materials, such as wood, metals and materials Ceramic Thus, for example these materials find application in fields as diverse as medicine (where they are used as prostheses, heart valves among many other applications), engineering (parts of vehicles and computers, boards, and hundreds of other applications) Agriculture. Polymers are also used in sports (balls, helmets, rackets) and in everyday objects, such as containers and utensils of all kinds. It is enough to look around us to realize that we are immersed in a world full of polymeric materials. The use and applications of these materials grows every day, so it is very important to know these materials as well as possible, not only for the advantages they offer, but also for the inconveniences they cause due to their accumulation when they are no longer usable tools.
For more information visit the following links.
- https://www.thoughtco.com/definition-of-polymer-605912
- https://plastics.americanchemistry.com/plastics/The-Basics/
- https://www.cmu.edu/gelfand/education/k12-teachers/polymers/natural-synthetic-polymers/
- http://www.wisegeek.org/how-is-nylon-made.htm
- http://www.craftechind.com/top-5-elastomers-gasket-seal-applications/
it is really informative post! I also belong to polymer field :)
Downvoting a post can decrease pending rewards and make it less visible. Common reasons:
Submit