Octamethylcyclotetrasiloxane (D4) is a volatile methylsiloxane (VMS) with a relatively low molecular weight. This silicone fluid has a silicon-oxygen bond in a cyclic arrangement and methyl groups are attached to the silicon atom. D4 can be used in the manufacture of silicone based polymers for use in medical devices and personal care products.

D4 can be polymerized through ring opening mechanism with a rare earth solid super acid as a catalyst for potential usage in the synthesis of vinyl coated polydimethylsiloxane (PDMS). It may also be used as a probe liquid for nuclear magnetic resonance cryoporometry (NMRC) to analyze the pore size distribution (PSD) of oil-bearing tight sandstone. Chemical vapor deposition (CVD) of D4 may be utilized for the preparation of siloxane based thin films.