Gas separation membrane made by plasma polymerization of 1,3‐ditrifluoromethylbenzene/CF4 mixture

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Abstract
Plasma polymerization of 1,3‐ditrifluoromethylbenzene (DTFMB)/CF4 mixture was investigated by means of elemental analysis and infrared spectroscopy and the permeation properties of the formed plasma polymer films were examined. The plasma polymerization deposited films containing fluorine atoms, of which the concentration depended on the starting composition of the DTFMB/CF4 mixture. The films were composed of fluorinated alkyl moieties with a small amount of fluorinated aromatic moieties and carbonyl moieties. The CF4 addition to DTFMB caused the breaking down of aromatic rings. Permeation properties of the plasma polymer films depended on the starting composition of the DTFMB/CF4 mixture, the discharge current, and the thickness of the deposited films. The permselectivity was enhanced by adding CF4 and increasing the discharge current. Plasma polymer films prepared from DTFMB/CF4 mixture containing 75 mol % CF4 at a discharge current of 150 mA had a permselectivity of 5.0 and an oxygen permeation coefficient of 3.5×10‐10 cm3 (STP) cm/cm2 s cm Hg.