organosiloxane

Organosiloxanes are a class of organosilicon compounds characterized by silicon–oxygen–silicon backbones with organic groups attached to silicon. The defining motif is the Si–O–Si linkage, which can form linear chains, cyclic rings, or highly crosslinked networks. They include linear siloxanes, cyclic siloxanes, and silicone polymers and resins. The term silicones is commonly used for many industrially important organosiloxanes.

In structure, silicon centers bear organic substituents such as methyl, phenyl, vinyl, or fluoroalkyl groups, and each silicon is linked through oxygen to adjacent silicon atoms. This architecture gives materials with a wide range of molecular weights and architectures, producing properties such as flexibility, thermal stability, chemical inertness, low surface energy, and good dielectric behavior. Polydimethylsiloxane (PDMS) is a widely known linear example; silicone oils, elastomers, and resins extend the family to fluids, gels, and crosslinked polymers used across industries.

Synthesis and curing typically rely on hydrolysis and condensation of silicon alkoxides or chlorosilanes to form Si–O–Si bonds. Controlled polymerization produces fluids or gums, while crosslinking reactions (such as hydrosilylation or condensation) create elastomeric or thermosetting networks. Room-temperature vulcanizing (RTV) silicones cure at ambient conditions, whereas others require heat.

Applications span lubricants, oils, sealants, adhesives, elastomers, medical implants, cosmetics, and electronics encapsulants and potting compounds. Safety profiles are generally favorable for many organosiloxanes, though certain cyclic siloxanes have raised environmental and regulatory concerns in some regions.