Silicone caulk can be used as a basic sealant against water and air penetration. In organosilicon and polymer chemistry, a silicone or polysiloxane is a polymer composed of repeating units of siloxane (−O−R 2 Si−O−SiR 2 −, where R = organic group).They are typically colorless oils or rubber-like substances.Silicones are used in sealants, adhesives, lubricants, medicine, cooking ...