ABSTRACT
Work on silicones began in the 1930s as an effort to combine the properties of glass (SiO2)n with the newly developed synthetic polymers. The silicones are polymers with the repeating unit (SiR2O)n where R is a hydrocarbon group, usually methyl. The starting material is (CH3)2SiCl2 but (CH3)3SiCl, CH3Si(Cl)3, and SiCl4 can be used to introduce terminal and branched positions. The linear polymers are relatively non-viscous and can be used as lubricants, while branched materials form rubbers, caulks, and coatings. The properties of silicones can be further modified by including other groups such as phenyl, fluoroalkyl, polyethylene glycol, or amino. Silicones with modified structures have a number of biomedical uses in catheters, implanted devices and contact lenses.
