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