4.3 Silicones 4.3.1 Structure and Properties, Nomenclature Silicones are compounds, in which silicon atoms, each linked to one more organic groups via carbon-siliconbonds, are linked to one another through oxygen atoms to produce straight chain, branched or crosslinked oligomeric or polymeric molecules. The simplest silicones are the a,w, bis-trimethylsiloxypolydimethylsiloxanes (see formula in the marginal notes)The name silicones, due to the American chemist Kipping, also extends to formulations of these polymers with other materials. According to IUPAC Rule D-6.2, the term siloxane is the name for oxygen compounds of the general formula H3Si- [O-SiH2],-O-SiH3, in which hydrogen can be replaced by organic groups. According to the provisional rules (Pure Appl. Chem. 53, 2283-2302 (1981) for the designation of organic macromolecules, polydimethylsiloxane should be named catena-poly(dimethy1-silicon)-p-0x0. The inter- national non-proprietary name for dimethylsiloxanes in cosmetic and pharmaceutical formulations is dimeticon. Poly(organosi1oxanes) are built up of a combination of the units R3Si01/2 (monofunctional, abbreviated to M), R2Si02/2 (difunctional, abbreviated to D), RSiOy2 (trifunctional, abbreviated to T) and SiO4/2 (tetrafunctional, abbreviated to Q). A combination of these units is chemically possible in the widest sense. In industrial silicone products R is generally a methyl- or a phenyl- group. linked to one or more organic groups via carbon-silicon Silicones = polyorganosil
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