Polymers have properties that depend on the chemicals they are made from, and the conditions in which they are made. Modern polymers have many uses, including:
- waterproof coatings
- fillings for teeth
- dressings for cuts
- hydrogels for making soft contact lenses and disposable nappy liners
- shape memory polymers for shrink-wrap packaging
Branches
Polymer molecules can have branches coming off them, which change the properties of the polymer.
Comparison of two types of poly(ethene)
| LDPE – low-density poly(ethene) | HDPE – high-density poly(ethene) |
---|
Branches on polymer molecules | many | few |
Relative strength | weak | strong |
Maximum useable temperature | 85ºC | 120ºC |
Plasticisers
Plasticisers are substances that let the polymer molecules slide over each other more easily. This makes the polymer softer and more flexible. For example, poly(chloroethene) or PVC is a hard polymer. Unplasticised PVC, usually called uPVC, is used to make pipes and window frames. PVC with plasticisers is soft and flexible. It is used for floor coverings, raincoats and car dashboards.
Slime
Poly(ethenol) is a polymer that dissolves in water to make slime. The viscosity of the slime can be changed to make it thick or runny by varying the amount of water.
POLYMERS

Powerpoint presentation
Polymers
A large molecule produced when small molecules join together. These small molecules are called monomers.
There are two types of polymers: natural and synthetic
•Natural Polymers:
The ones we find in nature: cellulose, starch, proteins nails, hair, bones, muscles, etc.
•Synthetic Polymers:
The ones that are man-made. Nylon, polystyrene (Styrofoam), polyesters, polyamides, PVC etc.
Polymerisation
It is the process of producing a polymer. There are two types of polymerisation
•Addition Polymerisation:
All the atoms in the monomer are used to form the polymer
Example:
Many molecules of Ethene
Polyethene (in presence of a catalyst and heat & pressure)
•Condensation Polymerisation:
All monomers join up forming a small molecules that are released in the process. Most of the time the molecule is water or a hydrogen halide. (Hydrogen chloride for example)
Many molecules of Aminoacid
protein + water
Addition Polymerisation
•during polymerisation, an alkene undergoes an addition reaction with itself.
•All the atoms in the original alkenes are used to form the polymer
•Long hydrocarbon chains are formed
The equation shows the original monomer and the repeating unit in the polymer




Condensation Polymerisation
Important: You should recognize the main functional organic groups used in polymerization

These functional groups can be in both sides of the molecules or combined.

Note: the green boxes between the functional groups are generic branches. We do not concentrate in this. We only look at the reaction within the functional groups and how the polimerisation takes place
In the condensation Polimerisation, different monomers get together and one of the following molecules will be produced (H2O or HCl)
We will study only 4 types of condensation polymers:
- Polypeptides, example: Proteins
- Polysaccharides, example: Starch
- Polyesters, example: Terylene
- Polyamides , example: Nylon
The monomers for the condensation polymers we will study are as follows:

Proteins
- When 2 aminoacids combine,they form a dipeptide.
- If three aminoacids combine, we have a tripeptide.
- With more of 30 aminoacids, we have a special polypeptides we call them proteins.
- chains can be lined up with each other
- the C=O and N-H bonds are polar due to a difference in electronegativity
- hydrogen bonding exists between chains. Many are Soluble in water.

Starch
- Starch is made of diols that get together to form the polymer

Polyesters
- Polyesters are formed by diols and dioic acids forming ester groups in each bond.

Polyamides
Nylon or Polyamides are groups of diamines and dioic acids. Both together form amide bond