Identify the repeat units and/or linkages in addition polymers and in condensation polymers

IGCSE Chemistry - Polymers: Addition and Condensation

IGCSE Chemistry 0620 - Organic Chemistry: Polymers

This page details the repeat units and linkages found in addition and condensation polymers, a key concept in organic chemistry.

Addition Polymers

Definition

Addition polymers are formed when monomers add together to form a polymer chain. This process typically involves unsaturated monomers, such as alkenes.

Repeat Units

The repeat unit in an addition polymer consists of the repeating structural formula of the monomer.

For example, in polyethylene, the repeat unit is -CH₂-CH₂-.

Linkages

The linkages in addition polymers are single bonds. The monomers are joined by the addition of atoms across the double bond of the monomer.

Examples

Polyethylene (plastic bags, bottles)
Polypropylene (containers, fibres)
Polytetrafluoroethylene (Teflon - non-stick coating)
Polyvinyl chloride (PVC - pipes, flooring)

Table: Addition Polymer Examples and Monomers

Polymer	Monomer	Repeat Unit
Polyethylene	Ethylene	`-CH₂-CH₂-`
Polypropylene	Propylene	`-CH₂-CH=CH₂-`
Polytetrafluoroethylene	Tetrafluoroethylene	`-CF₂-CF₂-`
Polyvinyl chloride	Vinyl chloride	`-CH₂-CH=CHCl-`

Condensation Polymers

Definition

Condensation polymers are formed when monomers join together, and a small molecule (e.g., water) is released as a byproduct.

Repeat Units

The repeat unit in a condensation polymer is a repeating structural formula, but it often includes functional groups that have reacted to form the linkage and release the byproduct.

Linkages

The linkages in condensation polymers are formed by the reaction of functional groups. Common linkages include ester, amide, and ether linkages.

Examples

Polyesters (e.g., PET - plastic bottles, clothing)
Polyamides (e.g., Nylon - textiles, ropes)
Polyurethanes (e.g., foams, coatings)
Polycarbonates (e.g., safety glasses, CDs)

Table: Condensation Polymer Examples and Monomers

Polymer	Monomer(s)	Repeat Unit	Byproduct
Polyester (PET)	Ethanoic acid + Ethylene glycol	`-COO-CH₂-CH₂-`	Water (`H₂O`)
Polyamide (Nylon)	Dicarboxylic acid + Diamine	`-CO-NH-`	Water (`H₂O`)
Polyurethane	Diisocyanate + Polyol	`-NH-CO-O-`	None (typically)
Polycarbonate	Bisphenol A + Phosgene	`-O-CO-O-`	Hydrochloric acid (`HCl`)

Suggested diagram: A diagram showing a simple addition polymer (e.g., polyethylene) with labelled repeat unit and linkages, and a simple condensation polymer (e.g., polyester) with labelled repeat unit, linkages, and byproduct.