Addition PolymersOption C.3

By: LW433

What is a polymer???

A polymer is a molecule composed of repeating monomers which are usually connected by covalent bonds.

These are models of monomers

When combined, they form a polymer

What does IB want us to know about Addition Polymers???

C.3.1 Describe and explain how the properties of polymers depend on their structural features.

Branching

There are two ways of classifying a polymer by the number of branches

it has. Low-density and High-density.

Get it? It looks like a tree!

Low-Density Polyethene (LDPE)

• Polymerized at high temperatures• Significant amount of branching• Molecules are prevented from packing close together• Flexible•Melts at about 85 degrees Celsius

High-Density Polyethylene (HDPE)

• Polymerized at low temperatures• Longer chains than LDPE• Molecules are able to pack more closely together• Melts at about 120 degrees Celsius•Rigid shape

Another way to classify polymers is by the positions of their alkyl groups.

Think back to Organics…

They were classified as being either “cis” or “trans”.

“Cis” was when the molecules were on the same side.

“Trans” was when the molecules were on opposite sides.

That same concept is applied

to addition polymers!

Isotactic refers to when the alkyl groups are all on the same side ofthe polymer strand.

Think “cis”.

Atactic refers to when the alkyl groups are on opposite sides of the polymer chain.

Think “trans”.

C.3.2. Describe the ways of modifying the properties of addition polymers.

Plasticizers

•Small molecules that can fit between long polymer chains•Weaken attraction between chains•Polymers become more flexible•Turn from rigid to completely pliable•Example: Polyvinyl chloride

Volatile Hydrocarbons

•Add pentane during formation of polystyrene•Heated in steam, the pentane vaporizes•Expanded polystyrene is produced•Light, good thermal material•Used as packaging

ALMOST DONE YA’LL

C.3.3. Discuss the advantages and disadvantages of polymer use.

ADVANTAGES

Polymers can be customized by

•Strength•Thermal and electrical insulation•Flexibility•Density•Lack of reactivity

DISADVANTAGES

Depletion of Natural Resources

•Most polymers are carbon based•Carbon comes from oil and coal•Both sources are limited

Disposal

•Lack of reactivity makes plastics not easy to dispose•They can be burned, but if not done properly, poisonous dioxins are produced•Hydrogen Cyanide and Hydrogen Chloride

Biodegradability

•Most plastics are not natural•Are not degraded by organisms•The anaerobic conditions of landfills make biodegradation very slow or cause it to stop.

That’s all folks!Good luck

on the IB test!