siloxane

A siloxane is any chemical compound composed of units of the form R2SiO, where R is a hydrogen atom or a hydrocarbon group. A siloxane has a branched or unbranched backbone of alternating silicon and oxygen atoms -Si-O-Si-O-, with side chains R attached to the silicon atoms.
The word siloxane is derived from the words silicon, oxygen, and alkane.

Fig.: Decamethylcyclopentasiloxane