TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: In the process, the heat is carried out at 300-650 degrees C, preferably 350-500 degrees C. Preferred Components: The polybenzoxazole membrane comprises a tricyclic repeating unit of formula (II). The polybenzoxazole membrane is in a configuration comprising flat sheet, disk, tube, and hollow fiber.Ring A = phenyl, biphenyl or diphenyl group of formula (aa);R1aa = -C(-CF3)2-, -C(-CH3)2-, -S(=O)2-, -O- or -S-; andring B = T    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The polymer containing aromatic sulfonic acid groups comprises poly(styrene sulfonic acid),and/or poly(trifluorostyrene sulfonic acid). The blend membrane comprises 0.05-20 wt.% of the polymer containing aromatic sulfonic acid groups. The aromatic polyimide polymer comprises poly(2,2'-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride-2,2-bis (3-amino-4-hydroxyphenyl)-hexafluoropropane) (poly(6FDA-APAF)), poly(3,3',4,4'-benzophenonetetracarboxylic dianhydride-2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane) (poly(BTDA-APAF)), poly(3,3',4,4'-benzophenonetetracarboxylic dianhydride-3,3'-dihydroxy-4,4'-diamino-biphenyl) (poly(BTDA-HAB)), poly(4,4'-oxydiphthalic anhydride-2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane) (poly(ODPA-APAF)), poly(3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride-2,2-bis (3-amino-4-hydroxyphenyl)-hexafluoropropane) (poly(DSDA-APAF)), poly(3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride-3,3'-dihydroxy-4,4'-diamino-biphenyl) (poly(DSDA-HAB)), poly(2,2'-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride-3,3',4,4'-benzophenonetetracarboxylic dianhydride-2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane) (poly(6FDA-BTDAAPAF)), poly(4,4'-oxydiphthalic anhydride-2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane-3,3'-dihydroxy-4,4'-diamino-biphenyl) (poly(ODPA-APAFHAB)), poly(3,3',4,4'-benzophenonetetracarboxylic dianhydride-2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane-3,3'-dihydroxy-4,4'-diamino-biphenyl) (poly(BTDA-APAF-HAB)), poly(2,2'-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride-3,3'-dihydroxy-4,4'-diamino-biphenyl) (poly(6FDA-HAB)), and/or poly(4,4'-bisphenol A dianhydride-3,3',4,4'-benzophenonetetracarboxylic dianhydride-2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane) (poly(BPADA-BTDA-APAF)). Preferred Definitions:    R1a = -C(CF3)2-;    X1 = phenoxybenzen-yl or diphenylmethanon-yl; and    X2 = 4-(2,2,2-trifluoro-1-(4-hydroxyphenyl)-1-(trifluoromethyl)ethyl)phenol group or acetic acid 4-(1-(4-acetoxy-phenyl) -2,2,2-trifluoro-1-trifluoromethyl-ethyl)-phenyl ester group.    EXAMPLE - 3,3',4,4'-Benzophenonetetracarboxylic dianhydride, 2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane, and 3,3'-dihydroxy-4,4'-diamino-biphenyl were mixed in a ratio of 3:2:1. Poly(2,2'-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride-3,3'-dihydroxy-4,4'-diamino-biphenyl) (poly(6FDA-HAB)) (2.5 g) and poly(3,3',4,4'-benzophenonetetracarboxylic dianhydride-2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane-3,3'-dihydroxy-4,4'-diamino-biphenyl) (poly(BTDA-APAF-HAB)) (2.5 g) were dissolved in a solvent mixture of N-methylpyrrolidone (16 g) and 1,3-dioxolane (9 g). The mixture was mechanically stirred for 2 hours to form a homogeneous casting dope. The resulting homogeneous casting dope was allowed to degas overnight to give poly(6FDA-HAB)/poly(BTDA-APAF-HAB) blend polymer membrane. The poly(6FDA-HAB)/poly(BTDA-APAF-HAB) polymer membrane was heated to 50-350 degrees C at a heating rate of 3 degrees C/minute under nitrogen gas flow. The membrane was held for 1 hour at 350 degrees C and then cooled down to 50 degrees C at a heating rate of 3 degrees C/minute under nitrogen gas flow to give polybenzoxazole (PBO) polymer membrane (PBO (6FDA-HAB/BTDA-APAF-HAB)-350).