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Concept
Silicone
Summary
A silicone or polysiloxane is a polymer made up of siloxane (−R2Si−O−SiR2−, where R = organic group). They are typically colorless oils or rubber-like substances. Silicones are used in sealants, adhesives, lubricants, medicine, cooking utensils, thermal insulation, and electrical insulation. Some common forms include silicone oil, silicone grease, silicone rubber, silicone resin, and silicone caulk.
Organosilicon compound
Stock and Somieski examined the hydrolysis of dichlorosilane, a reaction that was proposed to initially give the monomer H2SiO:
When the hydrolysis is performed by treating a solution of H2SiCl2 in benzene with water, and the product was determined to have the approximate formula [H2SiO]6. Higher polymers were proposed to form with time.
Most polysiloxanes feature organic substituents, e.g., [(CH3)2SiO]n and [(C6H5)2SiO)]n. All polymerized siloxanes or polysiloxanes, silicones consist of an inorganic silicon–oxygen backbone chain (⋯−Si−O−Si−O−Si−O−⋯) with two groups attached to each silicon center. The materials can be cyclic or polymeric. By varying the −Si−O− chain lengths, side groups, and crosslinking, silicones can be synthesized with a wide variety of properties and compositions. They can vary in consistency from liquid to gel to rubber to hard plastic. The most common siloxane is linear polydimethylsiloxane (PDMS), a silicone oil. The second-largest group of silicone materials is based on silicone resins, which are formed by branched and cage-like oligosiloxanes.
F. S. Kipping coined the word silicone in 1901 to describe the formula of polydiphenylsiloxane, Ph2SiO (Ph denoting phenyl, C6H5), by analogy with the formula of the ketone benzophenone, Ph2CO (his term was originally silicoketone). Kipping was well aware that polydiphenylsiloxane is polymeric whereas benzophenone is monomeric and noted the contrasting properties of Ph2SiO and Ph2CO. The discovery of the structural differences between Kipping's molecules and the ketones means that silicone is no longer the correct term (though it remains in common usage) and that the term siloxane is preferred according to the nomenclature of modern chemistry.
Official source
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