Gas Permeability of Plasma Polymerized Films Prepared from Various Organosilicic Compounds

In order to examine the effect of monomers on the gas permeability of plasma polymerized films, five kinds of organosilicic compounds (tetramethylsilane and the derivatives substituted by ethoxy groups) were used as the monomer, and plasma polymerized films were deposited on porous substrates. The gas permeability and IR spectra were measured. It was found that each plasma-polymerized films retained the chemical structures of the associated monomers. The ratio of oxygen to nitrogen permeation rates decreased with increasing the numbers of the substituted ethoxy groups. The membrane prepared from the monomer in which two ethoxy groups were substituted showed the highest value of the oxygen permeation rate. It was found that the oxidation state of Si in the monomer is the important factor in determining the gas permeability of the plasma polymerized films.