Preparation Of Polymers

Polymers are not readily available in nature, and therefore, they are often prepared synthetically at an industrial level. The polymer meaning is a long sequence of monomers that are first broken into fragments and joined together through covalent bonds. This is called polymerization. There are different types of polymerizations, but the most common one is linear polymerization, where chains of polymers combine to form one chemical substance. 

What is a Polymer?

A chemical compound that has repeating sequences of monomers is called a polymer. Knowing what a polymer is, is about knowing about the polymer’s meaning, about carbon and hydrogen atoms and the kind of bonds they form with one another. 

How to Define Polymer?

To define polymer, one must remember that it is synthetic, and natural polymers are difficult to find. Polymers can be defined as materials made up of large molecules, also known as macromolecules. Macromolecules are nothing but small chemical molecules that exist individually, called monomers. The polymers’ meaning is also no different. 

Preparation of Polymers

Polymers do not occur naturally, and they are always made synthetically. Synthetic polymers are usually produced through the chemical reaction of polymerization. There are various types of polymerizations. However, the primary purpose of any polymerization is to cause repeated chemical bonding of monomers, which are single compounds. These repeated bonds between several monomers result in polymer formation, and the process is called polymerization. 

Polymerization can happen through pressure, heat or catalysis to ensure chemical bonds between monomers are formed. Most polymerizations are in linear form. In the process of polymerization, there are also by-products. In some polymerizations, all monomers are joined together without leaving any part behind, but certain parts of monomers are left behind in some polymerizations. These are referred to as by-products of polymerization. Moreover, it is also possible that two polymers may combine and form an alloy during polymerization. The alloy shows the qualities of both the polymers it has originated from. 

Example of Polymerisation

The polymerization process or what is a polymer can be best understood through an example. Polymerization has a significant industrial use, particularly in the production of polyethylene. Polyethylene is nothing but the material through which plastic bags are made, which form the packaging of various goods like grocery items, toys, etc. Polyethylene is made from the monomer ethylene.

Ethylene comprises two carbon atoms and two hydrogen atoms attached through double bonds. Polyethylene has a chain of ethylene monomers bonded by their carbon atoms, and each carbon atom does not lose its two hydrogen atoms in polymerization. 

The process of making polyethylene is known as free radical polymerization. There are three steps in this process: initiation, propagation, and termination. In the initiation step, a catalyst must first be added to the required amount of monomer, ethylene. One of the most common catalysts is the benzoyl peroxide catalyst which can easily split the monomers into two portions. One is a free radical, and the other has an unpaired electron. These portions are also called the initiator fragments.

Since the fragment with an unpaired electron is the most unstable one, it is constantly looking for a carbon atom with which it can form double bonds. Hence, the initiator fragment with unpaired electron bonds with the carbon atom of another fragmented ethylene monomer. 

The next step in the process of polymerization is called propagation. While one radical is bonded, another one is formed. Therefore, the free radical bonds with the other carbon atom as well. There will be another free radical in the mix seeking a carbon atom. In this way, free radicals of different monomers attach to the carbon atoms of other monomers, thereby creating a chain of monomers that is called a polymer. In this step, the formation of free radicals ensures that the polymer chain keeps lengthening. 

Propagation keeps continuing when different chains keep attaching. Usually, the chains join one another in an end to end manner. But if they attach in the end to backbone manner, branched polymer molecules are formed, or in the case of this example, polyethene molecules will be branched. 

When the accessible radical stops seeking carbon atoms, the next and final termination step begins. The polymerization stops when the free radical, instead of taking an electron from a double-bonded carbon atom, takes away an entire hydrogen atom. This way, one end of the polymer chain does not have a hydrogen atom and to fill the void, the polymer chain forms a double bond with another carbon atom from another chain of the polymer. This is when polymerization ceases altogether. 

This is also called an additional polymerization because all the ethylene molecules are part of polyethylene’s final product. When some parts of monomers are not included in the final polymer, that process is termed condensation polymerization. The condensed polymer has less molecular weight distribution than the other polymer created through other types of polymerizations. 

Conclusion

Therefore, what is a polymer is a long chain of monomers that are joined together in polymerization. The best way to understand how polymers are prepared is through the example of polyethylene, which is a simple chemical compound to make. A certain quantity of monomers, ethylene, is broken down and bonded to form polyethylene.