Abstract: Disclosed is a method for the manufacture of film made of polymer based material that is particularly well suited to open-pore type cross-linked polymers. The disclosed method comprises the following steps: the making of a cell C comprising, between a substrate S.sub.1 and a substrate S.sub.2, a compound comprising a precursor of the polymer P, at least one of the substrates S.sub.1 and/or S.sub.2 being soluble in a solvent .SIGMA..sub.1 and/or a solvent .SIGMA..sub.2, said solvent .SIGMA..sub.1 and/or said solvent .SIGMA..sub.2 being a non-solvent for the polymer P; the polymerization of the polymer P within the cell C; the immersion of the cell C in the solvent .SIGMA..sub.1 and/or the solvent .SIGMA..sub.2 so as to eliminate the substrate S.sub.1 and/or the substrate S.sub.2. Applications: liquid crystal devices, molecular sensors.