Siloksaani

Siloksaani, or siloxane, is a class of organosilicon compounds defined by a backbone of alternating silicon and oxygen atoms, with organic substituents attached to silicon. The general structure features Si–O–Si linkages, and silicon atoms are typically further bonded to organic groups, giving linear, branched, or cyclic architectures. In polymers, repeating Si–O units form polysiloxanes such as polydimethylsiloxane (PDMS).

Two major categories are linear polysiloxanes and cyclic siloxanes. Linear polysiloxanes include common silicone oils and elastomers, known for their flexibility and stability. Cyclic siloxanes, such as octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5), are often used as feedstocks to produce polymers or as additives in formulations.

Properties of siloksaani compounds include high thermal stability, excellent chemical inertness, hydrophobicity, low surface energy, and good dielectric properties. They exhibit a wide temperature range of operation and low glass transition temperatures, making them versatile in lubricants, sealants, elastomers, and cosmeceuticals. They are generally chemically resistant to water and many solvents, and can act as slipping agents and barriers to gas and moisture.

Synthesis usually involves hydrolysis and condensation of silanols or organosilanes, or the polymerization of cyclic siloxanes through ring-opening reactions catalyzed by acids or bases. Crosslinking yields silicone rubbers and gels used in diverse applications.

Applications span industrial and consumer products, including lubricants, sealants, adhesives, cosmetics and personal care products, medical devices, and electronic encapsulants. Regulatory and safety considerations vary by compound and use; certain cyclic siloxanes have faced scrutiny due to environmental concerns in some regions.