TECHNOLOGY FOCUS - POLYMERS - Preferred Methods: The exposing involves using carbon-containing polymer precursor compounds and carried out at temperature of 10 - 60 (preferably 10 - 40, particularly 20 - 30)degreesC; pressure of 50 - 400 (preferably 50 - 300, particularly 95 - 105)kPa; and for 0.1 - 80 (preferably 0.2 - 70, particularly 1 - 24)hours. The exposing involves providing the polymer precursor compounds as a dense film. The method further involves removing the polar organic liquid from the treated polymer precursor compounds. The step of removing involves heating, desiccating, evaporating, drying, drying under vacuum, and drying using heated gas. The method further involves forming the membrane as a dense film, tube or hollow fiber. The step of pyrolyzing is carried out at 500 - 1500 (preferably 500 - 1400, particularly 800 -1200)degreesC and at 1 - 1600 9preferably 1 - 1000, particularly 1 - 10)Pa in vacuum or in the presence of inert gas. The pyrolyzing involves heating a dense film of polymer precursor film. The film has a thickness of 20 - 100 (preferably 30 - 80, particularly 30 - 50)microns. Preferred Components: The polymer precursor compound is selected from polycarbonate precursor, cellulosic polymer precursor, polyamide precursor, polyimide precursor, poly(amidimides) precursor, polyfurfuryl alcohol precursor, polyvinylidene chloride precursor, phenolic polymer precursor, polyacrylonitrile precursor, and/or polyetherimides precursor. The polar organic solvent has 1-6 carbon atoms (preferably alcohol, ether, aldehyde, ketone and/or carboxylic acid). The membrane comprises polyimide of formula (I).Ar1=quadrivalent organic group (preferably selected from benzene1,3,4,6-tetrayl, biphenyl tetra-yl, naphthalene tetra-yl, dibenzothiophene tetra-yl, dibenzothiophene 5,5-dioxide tetra-yl, pyrazine-1,3,4,6-tetra yl, anthracene tetra-yl, perylene-3,4,9,10-tetra-yl or group of formula (i));Ar2=aromatic diamine moiety (preferably selected from groups of formulae (Ia) - (Id));n=greater than 1;Z=-C(CF3)2-, -C(=O)-, O, S, -S(=O)2-, -C(CH3)2-, CH2 or groups of formula (ii);X, X1, X2 and X3=H, 1-5C alkyl, 1-5C alkoxy, phenyl or phenoxy. SPECIFIC COMPOUNDS - Methanol, ethanol, propanol, butanol, pentanol and hexanol are specifically claimed as the polar organic liquid.    EXAMPLE - No relevant example given.