Fabrication of freestanding nanoporous polyethersulfone membranes using organometallic polymer resists patterned by nanosphere lithography

A study was conducted to demonstrate a new method of fabricating freestanding porous polymer membranes using nanosphere lithography (NSL) with colloidal silica. The technique allowed the formation of highly ordered membranes with well-defined pore using poly(ferrocenylmethylphenylsilane) (PFMPS) as the etch resist. The adaptability of the method was demonstrated by the fabrication of freestanding polymer membranes, obtained by employing cellulose acetate (CA) as a sacrificial layer. Patterned poly(ferrocenylsilane) (PFS) that exhibited a thickness variation in a given pattern were prepared to demonstrate the approach. Asymmetrically substituted amorphous PFMPS was used to prevent undesired polymer crystallization that destroyed the etch mask. The fabrication process started by spin-coating a sacrificial CA layer on a silicon substrate followed by spin-coating of PES.