Silicones

The name “silicone” was initially used by chemist Frederic Kipping to describe chemicals he was creating and investigating in his laboratory. He reasoned that because silicon and carbon shared many characteristics, he should be able to synthesise compounds identical to those made with carbon and hydrogen. The technical term for these compounds was “silicoketone,” which he abbreviated to silicone.

Silicone is a polymer made of silicon and oxygen chains that repeat themselves. These polymers are formed up of inert synthetic chemicals like siloxanes, which are made up of silicon and oxygen atoms with carbon and hydrogen.

Polysiloxane is another name for silicone.

Structure of Silicone

Silicones are polymers having a silicon-oxygen backbone comparable to silicon dioxide (silica), but with organic groups connected to the silicon atoms via C-Si bonds. Organic groups are exposed to the outside by the silicone chain.

Silicones have physical properties that are similar to those of an alkane, despite having a highly polar chain. Because the -Si-O- bond energy is substantially higher than the C-C bond energy, the silicones – Si-O-  framework gives the polymers thermal stability similar to silica, allowing them to be employed in places where analogous organic materials would melt or degrade.

The presence of oxygen atoms in the silicone chain is indicated by the systematic name siloxane, which is named after the fact that it comprises a silicon atom, an oxygen atom, and is saturated like an alkane.

Siloxane bond

Silicones are versatile materials that possess both inorganic and organic properties. Silicones offer a variety of useful and distinguishing characteristics that are linked to their molecular structures.

Side chains of organic groups are connected to a main chain of siloxane bonds in every silicone-Si-O-Si- . The backbone of siloxane linkages is a property shared by inorganic materials including glass and quartz. Siloxane bonds have a substantially higher bond energy than the primary chains of organic polymers, which are formed byC-C and C-O bonds. Even at temperatures around 200⁰ C siloxane bonds will not break due to their high bond energy. They’re also chemically stable and have excellent heat and weather resistance.

Preparation method

The initial step in the creation of modern dimethyl silicone (polydimethylsiloxane) products is the preparation of dimethyl silicon dichloride, or dimethyldichlorosilane. 

The reaction takes place between elemental silicon and gaseous methyl chloride in a furnace at 300⁰ C.

The equation can be shown as:

Properties of silicones

1. Silicones with short chain molecules behave like oily liquids, silicones with medium chain molecules behave like viscous oils, jellies, and greases, and silicones with extremely long chain molecules behave like rubbery elastomers and resins.
2. They are chemically inert, meaning they are resistant to oxidation, heat breakdown, and organic reagent assault.
3. Silicones are water repellent in nature because they are surrounded by a non-polar alkyl group.
4. They are heat resistant and have a high dielectric strength, which means they are electrically insulating.

Silicones are widely utilised materials, owing to their excellent mechanical characteristics. Industry, chemicals, cosmetics, and medicine are just a few of the domains where they can be used.

Silicones have the following basic properties:

• Thermal resistance – this property allows silicones to be used in high or extremely low temperatures without losing their properties; non-flammability – this trait allows silicones to be used in conditions where there is a risk of fire;
• Chemical resistance – silicones can be mixed with oils and other chemicals thanks to this characteristic;
• Electrical insulators – Silicones are good electrical insulators and are frequently employed in the electronics sector as a result.

Applications

• It’s present in practically every form of oil and industrial lubricant, including engine oils and gear and engine lubricants.
• These chemicals are also essential resin constituents. Silicone’s structure and qualities provide the resin a more stable structure and make it a better binder.
• Commonly used in construction. It’s mostly used as a sealant and as a finishing (for example, to fill holes in corners). Silicones cure (at room temperature) into a solid, impermeable structure that fills gaps correctly and protects them from liquid intrusion.

Conclusion

Silicone is employed in a variety of industries and industrial processes due to its characteristics.

Highly specialised silicones are widely utilised in medicine, primarily in the manufacture of breast implants and dressings.

Silicones are found in many cosmetics and their constituents. They’re present in hair conditioners and shampoos, as well as a variety of other cleansing cosmetics and foundations.