making polymers

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Making Polymers


The word ‘polymer’ comes from the Greek words poly (meaning ‘many’) and meros (meaning ‘parts’).

Polymers are very large molecules made when hundreds of monomers join together to form long chains.

Plastics are synthetic polymers that can be shaped by heat or pressure.

What are polymers?


The materials that are used in every day life are made of either pure chemicals (elements or compounds) or mixtures of chemicals.

Where do materials come from?

Although pure metals are sometimes used in the manufacture of products, often mixtures of more than one metal are used as they have more useful properties.

Polymers are manufactured as pure compounds. However, other compounds are often added, which improve the properties of the plastic, for example, to make it more flexible.


Natural and synthetic materials


Materials from living things


Natural and synthetic polymers


Polymerization is the reaction used to convert monomers into polymers. The monomers in a polymer are joined together by covalent bonds between atoms.

In a covalent bond, each atom shares one or more electrons with another atom. The bonds are sometimes shown as lines.

What keeps the chain together?

covalent bond


How are monomers turned into polymers?

Making polymers


Many polymers are formed from alkenes, which are a family of hydrocarbon molecules with the general formula CnH2n.

Alkenes contain at least one double covalent bond between carbon atoms. The double bond makes them very reactive.

What are polymers made from?

The simplest alkene is ethene (C2H4).

The second simplest alkene is propene (C3H6).

double covalent

bond


How is polyethene made?


Addition polymerization

The process by which alkenes are joined together is called addition polymerization. All of the atoms in the alkene end up in the polymer so no other products are formed.

addition polymerizationmonomers

polymer

Addition polymerization involves the reaction of many unsaturated monomers (which contain a carbon-carbon double bond) to form a saturated polymer.


Drawing polymers – shorthand formulae

Polymers contain thousands of molecules, so how can their structures be easily drawn?

Part of the polymer molecule can be drawn:

A better way is to show a shorthand formula:

The ‘n’ means that the polymer contains a very large number of the repeating unit shown in the brackets.


What’s the polymer?

What is the shorthand formula for polypropene?

The monomer is propene (C3H6):

which canbe drawn as:

1. Draw two C atoms that were in the double bond with a single covalent bond.

2. Draw the brackets and the ‘n’.

4. Add the atoms that were attached to each C atom of the double bond.

3. Add the links outside the brackets.

polypropene


Naming polymers


Which polymer?


What’s the monomer?

What is the monomer of polyvinylchloride (PVC)?

1. Draw two C atoms joined with a double covalent bond.

2. Add the atoms attached to each C atom.

3. Draw the brackets and ‘n’.

The equation for the reaction can be drawn as:


Which monomer?


Glossary


Multiple-choice quiz