What is Condensation Polymerization?
Before jumping onto condensation polymers, let us understand what polymers are. Polymers, the word, in itself is self-explanatory. Poly means many, hence polymers are the agglomeration of monomers. Many monomers when combined together form a long chain of monomers.
What is Condensation?
Condensation is the chemical process of loss of small atoms from large monomers which help in the linkage of monomers to form large polymers. The atoms lost in the condensation process recombine with another atom to come out as molecules. Small molecules by-products are mostly water, oxygen, carbon dioxide or hydrogen gas.
To sum up, condensation polymers also known as step-growth polymers are the polymers that are formed when their monomeric units are subjected to condensation.
Condensation Polymers Examples
Condensation is one of the most profound methods of making polymers. Condensation polymerization is applied to make numerous polymers. Polyamides are one of the most important classes of condensation polymers like nylon 6,6. Other Condensation Polymerization examples include nylon 6, Kevlar, polyethylene terephthalate, etc. to name a few.
The pictorial illustration given below represents the generic reaction for the formation of a condensation polymer.
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The illustration below depicts the formation of one of the most important condensation polymer example: Nylon 6,6
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Nylon 6,6 is formed due to the condensation of two polyamides: Hexamethylenediamine and adipic acid. During the process, water molecules are eliminated from the monomeric units and they combine together to form nylon 6,6. So if you're asked to explain condensation polymers, you have your answer!
Condensation Polymerization Mechanism
The formation of condensation polymers takes more time than Addition Polymer formation. It is an endothermic reaction; the net heat exchange in the process is negative. This means that condensation polymer formation absorbs energy, hence the process often requires the provision of extra energy from an external source.
The monomers used in condensation polymers generally have two functional groups, namely amine and carboxylic acid. On the provision of external energy in the form of heat, 2 hydrogen atoms and an oxygen atom are lost, which come out together as a water molecule. Now that atoms are lost, empty valency is created for the formation of new bonds. New bonds are then formed between two monomers. This continues and hence results in a long chain of monomers. The monomer connection happens stepwise, unit by unit. Hence, the condensation Polymerization Mechanism is called step-growth polymerization. Let us understand this with a condensation polymer example:
A monomer of carboxylic acid functional group and amine functional group can join together through an amide linkage.
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During the formation of an amide linkage, a water molecule is lost and a bond is formed between adipic acid and Diaminohexane. An amine group remains at one of the terminal ends of the polymer whereas the other terminal end has a carboxylic acid group. Such a polymer is called a polyamide and in such a case, the byproduct is water. A popular example of polyamide is Nylon 6,6, the formation of nylon 6,6 is depicted pictorially in the reaction given above. The monomers of nylon 6,6 are Hexamethylenediamine and adipic acid.
Condensation Polymerization Examples
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Let us dive deeper into each condensation polymer example and understand them in a better way.
Nylon 6
Nylon 6 is another type of condensation polymer which is formed only by repeated polymerization of caprolactam. Caprolactam is a ring-shaped monomer which consists of amine linkages.
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During polymerization the ring-shaped monomer, caprolactam opens up and forms a long-chained polymer called nylon 6.
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Kevlar
Kevlar resembles a lot in structure with nylon 6,6. Although they are very similar, they have minute differences. The key difference is that the structure of kevlar does not contain amide linkages. Instead, they are joined together by benzene rings. The monomers of kevlar condensation polymer include benzene-1,4-dicarboxylic acid and 1,4-diaminobenzene. Given below are the structures of both the monomers of this condensation polymer example.
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On heating together these monomers condense and lead to the formation of kevlar. Given below is the structure of the kevlar condensation polymer.
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Polyesters
Polyesters are another important class of condensation polymers. Unlike other condensation polymers, polyesters arise from the condensation of carboxylic acid and alcohol. For example, polyethylene-terephthalate.
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Commonly abbreviated as PET or PETE, polyethylene terephthalate is one of the most widely used condensation polymers. We see its usage in numerous places in our daily lives. It's also one of the first condensation polymers to be discovered by scientists and has been in usage for a long time now.
FAQs on Condensation Polymers
Q1. What are Some of the Most Renowned Condensation Polymer Examples and What is their Application?
Ans. If we see around, we will find numerous daily use items made of condensation polymers. Condensation polymers have a wide scope of usage and are used in various places. For instance,
Bakelite: Bakelite is a condensation polymer which is used in making various materials. They're mainly known for their electrical resistivity and heat resistivity. They're used in making electrical insulators, radios, telephones and a wide variety of kitchen use products
Melamine: Melamine is another popular polymer. The polymer is mainly known for its fire-resistant properties. Melamine is used for making fireproof materials, dinnerware and other heat resistant products.
Q2. Are there Naturally Occurring Condensation Polymers?
Ans: If we peep into nature, we can find many evident examples of naturally occurring condensation polymers. The popular examples of naturally occurring condensation polymers are:
Cellulose: Cellulose is a key element of the plant's structure. It forms a fair share of the plant body. Plants store their excess energy in the form of cellulose. This cellulose is an example of a natural condensation polymer. Cellulose also is the major component of the cell wall. They are a long chain of peptide-protein linkage.
Poly (β-hydroxybutyric acid): This is another example of a naturally occurring condensation polymer. The polymer is produced largely by certain bacteria which are mainly found in soil and water.
