9.17-9.25 - Polymers

A substance of high average relative molecular mass made up of small repeating units

In a polymerisation reaction (with ethene as the monomer) ethene’s C=C double bond breaks open to allow ethene molecules to join together to form a single product. This is an example of an addition reaction and results in the production of poly(ethene). The repeat unit has the same atoms as the monomer because no other molecules are formed in the reaction. Therefore the repeating unit is just the structural formula of ethene but with a single rather than double bond and square brackets with a horizontal line through the middle surrounding it. There is as a ‘n’ on the bottom right side

Other addition polymers can be made by combining together other monomer molecules that contain double carbon bonds.

-Poly(propene) -Poly(chloroethene) (PVC) -Poly(tetrafluoroethene) (PTFE)

Properties: Flexible, cheap, good electrical insulator Uses: Plastic bags, plastic bottles, cling film, poly tunnels, coating on electrical wires

Properties: Flexible and strong, doesn’t shatter Uses: Buckets, crates, bowls, ropes, carpets

Properties: Tough, good insulator, cheap, long-lasting, can be made hard or flexible Uses: Window frames, gutters, pipes, insulation for electrical wires

Properties: Tough and non-stick, slippery Uses: Non-stick coating for frying pans and other kitchen utensils, burette taps, stain-proofing clothes and carpets

In condensation polymerisation, each time a bond is formed between two monomers a repeat unit from a condensation polymer and a small molecule is released. Alcohol and carboxylic acid functional groups react, releasing a molecule of water.

A polyester is formed when a monomer molecule containing two carboxylic acid groups is reacted with a monomer molecule containing two alcohol groups.

A molecule of water is formed each time an ester link is formed because the OH and H groups combine to make H₂O

Synthetic polymers are derived from petroleum oil. The extraction of oil can damage the environment; oil produces greenhouse gas emissions and oil spills can harm sea creatures and make them unsafe to eat.

Polymers are formed by the joining up of many small molecules with strong covalent bonds.These strong covalent bonds make polymers unreactive and chemically inert so they are usually non-biodegradable. This means they are persistent in landfill sites and cause the sites to fill up quickly as decomposers cannot break them down.

Different polymers must be separated from each other and sorted into different types before being melted and reformed into a new product. This can be difficult and expensive to do.

Waste polymers can be incinerated. This involves combustion at very high temperatures. -Carbon dioxide is produced, a greenhouse gas which contributes to global warming. -Polymers which contain chlorine such as PVC release toxic hydrogen chloride when burned. -If polymers are incinerated by incomplete combustion, carbon monoxide may be released, which is harmful to the respiratory system.

Advantages: -Reuses waste materials which is better for the environment than burning them, which can produce greenhouse gases or landfill which disrupts the environment -It saves crude oil, which is a finite resource and reduces the volume used -More economically viable than making more polymers

-DNA is a polymer made from four different monomers called nucleotides. -Starch is a polymer based on sugars. -Proteins are polymers based on amino acids