polymerisation

• Addition polymerisation is one of the most important addition reactions of alkenes which form the basis of the plastic industry.
• Addition polymerisation is the reaction in which many monomers containing at least one C-C double bond form long chains of polymers as the only product.
• In addition polymerisation, the π-bond in each C-C bond breaks and then the monomers link together to form new C-C single bonds.
• A polymer is a long-chain molecule that is made up of many repeating units.
• The small, reactive molecules that react together to form the polymer are called monomers.
• A polymerisation reaction can be represented by a general formula or by using displayed formulae.
• Poly(ethene) and poly(chloroethene) (also known as PVC) are polymers made up of the ethene and chloroethene monomers respectively and are commonly used in making plastics.
• Poly(alkenes)s are very large alkane molecules which are unreactive and do not undergo any chemical reactions.
• Due to their unreactivity, poly(alkenes)s are non-biodegradable and take hundreds of years to decompose when dumped in landfill sites.
• Poly(alkenes)s are extremely important in everyday life, particularly their use as plastics.
• The disposal of poly(alkenes)s is problematic due to their large size, unreactive nature, and non-biodegradability.
• Throwing away poly(alkenes) causes long-term pollution of the environment.
• Burning poly(alkenes)s results in harmful combustion products which cause the pollution of the environment.
• The disposal of polymers is a challenge due to their unreactivity, their non-biodegradability, and the formation of harmful combustion products when burnt.
• When ethenol (CH(OH)=CH ) is polymerised, the C-C double bond opens to produce a repeating unit of CH(OH)-CH.
• To find the monomer, the repeating unit should be deduced.
• When ethene-1,2 − diol (CH(OH)=CH(OH)) is polymerised, the C-C double bond opens to produce a repeating unit of CH(OH)-CH(OH) which gives the polymer poly(ethene-1,2 − diol).
• Repeating units have only 2 carbons in the polymer main chain.
• The section of the polymer chain shown inside the square brackets by the structural or displayed formula is the repeat unit and not the monomer.
• The repeating units of poly(ethene) and poly(chloroethene) are similar to their monomer except that the C=C bond has changed into a C-C bond.
• Again, the repeating unit only has 2 carbons in the polymer chain which in this case are two carbon atoms that each contain one OH group.
• The monomer is the same as the repeat unit except for that it has C=C bonds instead of C-C bonds.
• In poly(alkenes) (such as poly(ethene)) and substituted poly(alkenes) (such as PVC) made of one type of monomer, the repeating unit is the same as the monomer except that the C-C double bond is changed to a C-C single bond.