Polymers  Elmhurst College
Addition Polymers Rubber  Chemistry Department
Condensation Polymers Silicone    Virtual ChemBook

Silicone Polymers

Silicone Polymers:

Silicone polymers do not have carbon as part of the backbone structure. The although silicon is in the same group as carbon in the periodic table, it has quite different chemistry.

Many silanes are known which are analogous to the hydrocarbons with Si-Si bonds. These compounds are not very stable and hence not very useful.

Silicones on the other hand have an alternating -Si-O- type structure. This basic structural unit is found in many rocks and minerals in nature including common sand.

Various organic groups such as methyl or the benzene ring may be bonded to the silicon as shown in the graphic on the left.

Silicones are water repellent, heat stable, and very resistant to chemical attack. They find many uses in oils, greases, and rubberlike materials. Silicone oils are very desirable since they do not decompose at high temperature and do not become viscous. Other silicones are used in hydraulic fluids, electrical insulators and moisture proofing agent in fabrics.

Silicones have a number of medical applications because they are chemically inert. A good deal of controversy has involved the the use of silicone in polyurethane bags as breast implants. Again they were used because they were thought to be very inert and resistant to dissolving or other reactions. Reports have cited increased cancer risk and severe immune responses from possible leakage of the silicone from the implants. Some scientists dispute these findings.

Link to Silicones - with Chime molecule - Macrogalleria at U. Southern Mississippi

Superball Demonstration:

The liquids solution of sodium silicate is already in the form polymer. The silicate is alternating atoms of silicon and oxygen in long chains. When the ethanol is added, it bridges and connects the chains by cross-linking them. The analogy of a chain-link fence is a good picture of the idea of chains that are cross linked. That is what the ethanol and the silicate are doing to form this super ball.

Silicon type Polymers
Demonstrations with Polymers