Polymers

Polymers are large molecules made up of repeating subunits called monomers.
There are a wide variety of polymers, each with different properties and uses, ranging from common substances like plastics to biological polymers like proteins and DNA.
Factors that affect the properties of a polymer include the nature of the monomers used, the length of the polymer chain, and the degree of branching or cross-linking between chains.
Many polymers, such as polyethylene and polypropylene, are made from simple hydrocarbon monomers, but others, including proteins, are made from complex monomers with specific functional groups.

Polymerization

The process of forming a polymer from monomers is known as polymerisation.
There are two main types of polymerisation: addition polymerisation and condensation polymerisation.
In addition polymerisation, the monomers simply add together to form the polymer, with no other products.
In condensation polymerisation, two different types of monomers react together, with the elimination of a small molecule, usually water.

The physical properties of polymers and their behaviour under different conditions can be altered by changing the nature of the monomers used and the conditions of polymerisation.
For example, the degree of crystallinity in a polymer, which is associated with rigidity and high melting point, can be increased by slowing down the rate of cooling after the polymer is formed.
Polymers can be broadly divided into thermosetting and thermoplastic types.
Thermosetting polymers are cross-linked and cannot be remoulded on heating, while thermoplastic polymers can be remoulded multiple times upon heating.
Polymers have a wide range of applications, from packaging materials to insulation wires, medical appliances, clothing and more.