Atmospheric-Pressure Plasma-Induced In Situ Polymerization of Liquid Silsesquioxane Monomer for the Synthesis of Polysilsesquioxane Nanocomposite Membranes with Sub-Nanometer Pores for Molecular Separation

Plasma-induced polymerization of liquid silsesquioxane monomer (1,2-bis(triethoxysilyl)ethane, BTESE) at the gas–liquid interface was achieved at room temperature by employing an atmospheric-pressure plasma jet. The polymerization of the liquid monomer under exposure to atmospheric-pressure plasma resulted in the formation of a thin polysilsesquioxane layer at the immediate surface of the porous support. The confined polymerization at the plasma-liquid interface was demonstrated to be beneficial for preparing nanocomposite membranes with a thin selective layer on top of the porous support. The BTESE-derived polysilsesquioxane membrane exhibited high selectivity for gas separation (H 2 /CH 4 = 195) based on the molecular sieving mechanism.