Polymers

Polymers:

A polymer is defined as a macromolecule, formed by the combination of a large number of small molecular units called monomers.

Monomers:

They are the small molecular weight molecules that combine to form macromolecules called polymers. The process of the combination of same or different small molecular weight monomers to form giant polymers is known as polymerization.

n CH₂ =CH₂

Classification of Polymers:

1. On the basis of polymerization:

1. Addition polymers: Those polymers which are formed by repetition of monomers without losing any molecule are called addition polymers. 

Examples: polythene, polystyrene (formation of benzene from acetylene), etc.

1. Condensation polymers: These are the polymers formed by the combination of monomers by the elimination of small molecules like H2O, HCI, NH3, etc. 

Examples: Nylon, Bakelite, etc.

1. On the basis of monomer unit:

1. Homopolymer: These are the polymers made up of the same type of monomer units.

Examples: Polythene, PVC, etc.

1. Copolymer: These are the polymers made up of more than one type of monomer units.

Examples: Bakelite, Nylon-6,6, etc. 

1. On the basis of source or origin:

1. Natural Polymer: These are the polymers obtained from natural sources, i.e. plants and animals. 

Examples: protein, starch, natural rubber (obtained from iso-proprene i.e. latex of rubber trees), etc.

1. Synthetic Polymer: These are the polymers obtained artificially in the lab. 

Examples: Polyethene, PVC, Bakelite, Nylon-6,6, etc.

1. On the basis of behavior on heating:

1. Thermosetting Polymers: These are the polymers which turn hard and rigid on heating.

Example: Bakelite

1. Thermoplastic Polymers: These are the polymers which become soft on heating and regain their properties on cooling.

Examples: Polyethene, PVC, etc.

1. On the basis of intermolecular forces:

1. Elastomers: These are the polymers where polymer chains are held together by weak intermolecular hydrogen bonds and are elastic in nature.

Example: Rubber, Buna-S, etc.

1. Fibers: These are the polymers where polymer chains are held together by strong intermolecular hydrogen bonds. 

Example: Nylon-6,6

1. Thermoplastics: They are the polymers having intermolecular forces intermediate between elastomers and fibers. 

Examples: Polystyrene, Polyethene, etc.

1. Thermosetting Polymers: These are the polymers having highly cross-linked and the strongest intermolecular forces. 

Example: Bakelite

Some Common Polymers:

Polymer:	Monomer:	Structure of Polymer:	Uses:
Polyethene	Ethene (CH2=CH2)	-(CH2-CH2)n-	Making polyethene bags, buckets, etc.
Polyvinyl Chloride (PVC)	Vinyl Chloride (CH2=CH-Cl)		Making toys, raincoats, pipes, etc.
Teflon (PTFE) or Fluon	Tetrafluoroethene (CF2=CF2)	-(CF2-CF2)n-	Non-sticky coatings, gasket, valves and artificial limbs
Polystyrene	Styrene		Disposable food containers, plastic cups, insulation, etc.
Dacron	Pterethalic Acid Ethylene Glycol
Nylon-6,6	Adipic acid [HOOC-(CH2)4-COOH] and Hexamethylenediamine [-H2N-(CH2)6-NH2]	-[OC-(CH2)4-CONH-(CH2)6-NH2]n-	Making fabrics, carpets, ropes, etc.
Bakelite	Formaldehyde [HCHO] Phenol	below

Structure of Bakelite: