Preparation of Microporous Silicone Rubber Membrane with Tunable Pore Size via Solvent Evaporation-Induced Phase Separation

Silicone rubber membrane with ordered micropores in the surface was prepared by means of the solvent evaporation-induced phase separation. A ternary solution including liquid silicone rubber precursor, liquid paraffin, and hexane was cast to form a film with a two-phase structure after the hexane was evaporated. The micropores were generated by removing liquid paraffin phase in the cured silicone rubber film. The effects of the liquid paraffin concentration, casting temperature, initial casting solution thickness, air circulation, and addition of surfactant Span-80 on the pore structure in the membrane surface were investigated. The average pore size increases with increasing liquid paraffin concentration or the initial casting solution thickness. The formation of pore structure in the membrane surface is related to the phase separation and thus the phase separation process of the casting solution surface was in situ observed using the digital microscope. The formation mechanism of pore is attributed to a nucleation, growth, and coalescence process of liquid paraffin phase in the membrane surface.