Organic polymers are important in living organisms because they provide basic structural components and participate in key life functions. For example, protein, which is a polymer of amino acids, plays an important role in the cellular function of our bodies. Polymers are extensively used in almost every industry, from manufacturing to the medical field. 

They are prized for their diverse qualities, which enable them to serve many purposes. Our bodies are made up of polymers. Plants are made up of cellulose, a polymer. Life as we know it would cease to exist if polymers were to vanish suddenly.

Polymers can be fine-tuned to make use of particular favourable qualities depending on the intended purpose. Some of the properties of polymers are as follows: 

Impact resistance: Tough plastics that can survive rough treatment are ideal for baggage, protective cases, and automotive bumpers.

Brittleness: Some types of polystyrene are rigid and brittle, easily bending with heat.

Ductility: Ductile polymers can bend without breaking and have a variety of applications.

Elasticity: Natural and synthetic rubbers are both stretchy, making them perfect for car tyres and other comparable products.

Polymers are classified in many ways owing to their large number, diverse properties, and ability to exist naturally or synthetically:

1. Source-based classification

Polymers are first classified according to their source of origin.

• • Natural polymers
    Polymers derived from nature or ones that naturally arise are called natural polymers. Some examples of natural polymers are cellulose, rubber, and protein. 
  • Synthetic polymers
    Synthetic polymers are created or synthesised in a lab. These are manufactured commercially for human use. Some examples include polyethylene, polyester, Bakelite, and nylon. 
  • Semi-synthetic polymers 
    Semi-synthetic polymers are created in a lab by chemically altering natural polymers. These commercially significant polymers are created in a controlled setting. Vulcanised rubber and rayon are examples of semi-synthetic polymers. 

2. Structure-based classification

Polymers can be classified into three categories based on their structure:

• • Linear polymers
    Linear polymers have a structure that resembles a continuous straight chain with similar links connecting them. These are made up of monomers bonded together to form a lengthy chain. Polyvinyl chloride (PVC), commonly used in electrical cables and pipes, is an example of a linear polymer. 
  • Branched-chain polymers
    Branched-chain polymers are those in which the linear chains of a polymer form branches. Monomers unite to produce a long straight chain with a few shorter branching strands. Plastic bags made of low-density polyethylene (LDPE) are one example of a branched-chain polymer.
  • Cross-linking polymers
    Cross-linking polymers are made up of monomers bundled together to create a three-dimensional structure. The monomers in cross-linking polymers have strong covalent bonds. The molecules are bifunctional and trifunctional. Bakelite (used in electrical insulators) is a good example of a cross-linking polymer.

3. Polymerisation mode-based classification

Polymerisation is a chemical reaction that results in the formation of a long, three-dimensional network of polymers from two or more monomers.

Polymers are classified as follows based on the type of polymerisation:

• • Addition polymerisation
    In addition polymerisation, monomers react to generate a polymer without forming byproducts. Addition polymers usually have double or triple bonds. The formulas of addition polymers are always the same as those of their monomers. Ethene CH₂=CH₂ to polyethylene -(CH₂-CH₂)n- is an example of addition polymerisation. 

  • Condensation polymerisation
    In condensation polymerisation, smaller molecules or monomers react with each other to generate large polymers along with forming byproducts like water or methanol. An example of condensation polymerisation is the reaction of hexamethylenediamine and adipic acid to produce Nylon-66, where molecules of water are released as a byproduct.

4. Molecular forces-based classification
   The forces that keep atoms together within a molecule are known as intramolecular forces. The strength of the interactions between molecules contributes to the distinct properties of polymers. 

Polymers can be divided into four groups using this method.

• • Elastomers
    Elastomers are viscoelastic substances with weak intramolecular forces. For example, rubber. 

  • Fibres
    Fibres are strong, robust, have superior mechanical properties, and have significant intramolecular force. For example, Nylon-66. 

  • Thermoplastics
    Thermoplastics exhibit moderate attraction or intramolecular forces. For example, polyvinyl chloride. 

  • Thermosetting polymers
    Thermosetting polymers significantly increase the mechanical characteristics of the material, improving chemical and thermal resistance. For example, phenolics and silicones.

A copolymer is a polymer composed of at least two monomer species, frequently used to enhance or modify the qualities of plastics. Copolymers make up a large percentage of commercially significant polymers. Examples include polyethylene-vinyl acetate (PEVA) and nitrile rubber.

A homopolymer, on the other hand, is a polymer composed of only one monomer unit. Some examples of homopolymers are polythene, polypropylene, and polyvinyl chloride.

Rubber vulcanisation is a technique that improves the flexibility and stability of rubber. The rubber is heated in the presence of sulphur, resulting in a three-dimensional cross-linking of chain rubber molecules connected by sulphur atoms. Vulcanised rubber is used in a wide range of items, from tyres, clothing, and accessories to footwear and gaskets.

Vulcanised rubber is substantially stronger than regular rubber. Many manufacturing organisations opt for vulcanised rubber because it can handle more strain. Vulcanised rubber is also more flexible than non-vulcanised rubber. There is no correlation between flexibility and strength, but vulcanised rubber is strong and flexible. Thanks to its improved elasticity, it can be stretched to a larger extent without permanent distortion.

Biodegradable polymers can undergo decomposition in a few days owing to the action of microbes. Nylon 2–Nylon 6 and polyhydroxy butyrate are two examples of biodegradable polymers.

Non-biodegradable polymers do not undergo decomposition when exposed to microbes. They are made up of lengthy carbon and hydrogen atom chains. These molecules form an unbreakable interatomic link, making it difficult for microorganisms to separate the molecules. As a result, decomposition takes a long time. Polytetrafluoroethylene (Teflon) and polyethene are two examples of non-biodegradable polymers.

Polymers are large molecules that form the basic constituent of various objects and materials around you. The industrial and economic importance of polymers is astounding. Researchers are currently investigating more methods to enhance and develop the use of polymers in a variety of sectors. Class 12 students can access more chemistry content on the MSVGo app. Download the MSVGo app for more quality content like this.