7.3.1 Addition Polymerisation

Alkenes, such as ethene and propene, can undergo addition polymerisation to produce polymers like poly(ethene) and poly(propene).

In addition polymerisation, the process involves the joining together of many small molecules called monomers to form very large molecules known as polymers. This occurs through the breaking of the carbon-carbon double bond in the monomer and the formation of new single bonds between the monomers. The reaction is initiated by the use of a catalyst, such as a radical initiator, which starts the polymerisation process.

In the resulting addition polymer, the repeating unit within the polymer chain has the same atoms as the original monomer because no other molecule is formed during the reaction. For example, in the case of poly(ethene), the repeating unit is (-CH₂-CH₂-)_n, where n represents the number of repeating units in the polymer chain.

The repeating unit in the polymer chain is derived from the monomer. The repeating unit reflects the structure of the monomer, as no other molecule is formed during addition polymerisation.

Addition polymerisation allows for the production of a wide range of useful and versatile polymers. These polymers possess unique physical and chemical properties, making them suitable for various applications. For instance, poly(ethene) is commonly used in the production of plastic bags, bottles, and containers, while poly(propene) (also known as polypropylene) finds applications in packaging, textiles, and automotive parts.

Addition polymers can be identified by the presence of long chains of repeating units, while monomers can be identified by the presence of a carbon-carbon double bond (C=C) in their structure.