Porous polyelectrolyte multilayer (PEM) films with pore size control ranging from nano- to micro-scale are made hydrophobic by coating with fluorine compounds. A layer-by-layer (LbL) technique is used to fabricate PEMs, and the built up PEMs are subject to subsequent porous treatment under acidic or basic conditions. Besides shortening the processing time, polyelectrolytes with high molecular weight are used for the first time. Multi-scale porous structures are provided with either micro-sized porous structure on top of nano-sized porous structure or the other way around.
