Soap, Detergents and Polymers: Types of Polymers and Polymerization (For CBSE, ICSE, IAS, NET, NRA 2022)

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Polymer

  • A Polymer is a giant molecule formed by inter molecular linkage between same or different types of smaller molecules called monomers. A polymer may be obtained from two monomers.
  • For example, polyethene is a polymer of the monomer ethylene .
  • Monomers are the small molecule which are capable of linking amongst them- selves to form big molecules called polymers.

Types of Polymers

Homopolymer

A polymer formed from only one kind of monomers is called homopolymer. Polyethene is an example of homopolymer.

Copolymer

  • A polymer formed from more than one kind of monomer units is called copolymer or mixed polymer.
  • For example, Buna-S rubber, which is formed from 1,3- butadiene and styrene is an example of copolymer.

Polymerization

The process by which the monomers get linked up is called polymerization.

Polymerization is represented as:

The Process of Polymerization

where M stands for the monomer.

Types of Polymerization

Addition Polymerization

  • This process involves the addition of monomer units to themselves to form a growing chain by a chain reaction mechanism. It is for this reason that the process is also known as chain growth polymerization.
  • For example, benzoyl peroxide provides free radical ‘benzyl’ to initiate the chain polymerization reaction.
Addition Polymerization

Initiation,

Addition Polymerization

These free radicals (R) then attack the unsaturated monomer and form a new free radical which goes on successively adding monomers and thus grows the chain, this is called Chain propagation.

Addition Polymerization

The final termination of the two growing chains leads to a polymer. This is called chain termination:

Addition Polymerization

Condensation Polymerization

In this, the monomers combine with the elemi-nation of a small molecule like , or , etc. The reaction is called (step growth) condensation polymerization and the product formed is called con-dentation polymer.

Condensation Polymerization

The process involves the elimination of by product molecules, therefore, the molecular mass of the polymer is not the integral multiple of the monomer units.

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