Si containing polymers have been instrumental in the development of membrane gas separation practices since the early 1970s. Their function is to provide a selective barrier for different molecular species, where selection takes place either on the basis of size or on the basis of physical interactions or both. Combines membrane science, organosilicon chemistry, polymer science, materials science, and physical chemistry   Only book to consider polymerization chemistry and synthesis of Si-containing polymers (both glassy and rubbery), and their role as membrane materials   Membrane operations present environmental benefits such as reduced waste, and recovered/recycled valuable raw materials that are currently lost to fuel or to flares