1. Organic Chemistry
Lesson # 4 - Polymers

2. Polymers
Polymers are large molecules that are made by linking together many smaller molecules. These small individual molecules are called monomers. Polymer comes from two Greek words meaning “many parts.”
The monomers can be identical, or two or more monomers may occur in a repeating pattern.
Polymers can be linked in different ways, depending on the type of small units and the linkages. In this way, we can produce materials with desired properties, such as strength, flexibility, transparency, and chemical stability.
Plastics are synthetic polymers, but there are natural polymers as well. Complex carbohydrates are polymers of sugar, proteins are polymers of amino acids, and DNA is a polymer of small units of genetic material.

3. Addition Polymers
Addition polymers result from the addition reactions of monomers that contain double or triple carbon to carbon bonds.
High heat, pressure, and a catalyst are required to break the double or triple bond and join all of the carbons together in addition polymers.
Some polymers are stronger than others as they contain crosslinks, which are bonds between neighbouring chains. Increasing the number of crosslinks increases the rigidity of the material.
Addition polymers are chemically unreactive, which makes them ideal for use as containers for chemicals and food. They are also flexible and mouldable, as there are only weak intermolecular forces holding the chains together.

4. Uses of Addition Polymers
Polyethene (old name is polyethylene) is one of the simplest plastics, and is used for insulating electrical wires and plastic containers. It is a repeating chain of ethene monomers.
Polypropene – food packaging, plastic parts, lab equipment, automotive parts
Polychloroethene – also called polyvinylchloride (PVC) – building materials, piping, etc.
Polytetrafluoroethene – PTFE – is very inert (doesn’t react) and it is stable at temperatures of about -50°C to over 300°C (it doesn’t burn). PTFE is often used as a lubricant, and has the name Teflon.

5. Condensation Polymers
Condensation polymers are formed similarly to how esters and amides are formed – through a condensation reaction where water or some other small molecule is removed.
For these polymers to form, the monomer molecule must have two functional groups – one at each end of the molecule. These can include carboxyl groups, hydroxyl groups, and amine groups.
Condensation polymers quite often form at room temperature and pressure, so are produced fairly cheaply in an industrial situation.

6. Uses of Condensation Polymers
An example of condensation polymerization is nylon. Nylon was produced in the 1930’s by the American chemist, Wallace Carothers, as a synthetic alternative to silk. Uses of Nylon include clothing, footwear, pantyhose, toothbrush bristles, fishing lines, Velcro, carpet, air bags, parachutes, guitar strings, sports strings, auto/machine parts
Intermolecular bonds play an important part in the properties of condensation polymers, resulting in exceptionally strong fibres.
An example of a strong condensation polymer is Kevlar – it is stronger than steel and heat-resistant, yet it is lightweight enough to wear. It is used to make products such as aircraft parts, sports equipment, protective clothing for firefighters, and bulletproof vests for police officers.