TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The primary aliphatic amine is monoethanolamine, ethylamine, propylamine and/or butylamine. The primary aliphatic amine, secondary amine or tetramethylammonium hydroxide are in a solution of alcohol (methanol, ethanol, isopropanol or butanol), hydrocarbon, ketone and/or water. The poly(aryl ether) is polyphenylene oxide, or polysulfone (such as polyether sulfone (preferred), bisphenol A based polysulfone or biphenol based polysulfone). The polyimide is poly(ether imide) of formula (A and B) or phenylindane containing polyimide. (I) is a flat sheet, a tubular or a hollow fiber fluid separation membrane (microfiltration, ultrafiltration, nanofiltration or gas separation membrane). The fluid separation membrane further contains a separation layer formed on top of the flat sheet, tube or hollow fiber surface.Preferred Process: The process of forming a shaped configuration is accomplished by extrusion, casting or molding. The step of decomposing the polyimide and removing the low molecular weight fragments take place concurrently in a common liquid media. The preparation of (I) further comprises drying the porous article under conditions that substantially preserves the porous structure. The drying process is carried out by removing a hydrocarbon, or a fluorocarbon solvent from the porous article. The blend contains at least one additive (such as solvent, a plasticizer, a catalytic particle or a filler). (I) is a multilayer article (contains two or more layers (the layer comprised of the smaller average pore size is supported or sandwiched between layers with the larger average pore size) that differ in the average pore size) formed from two or more poly(aryl ether)/polyimide blends that differ in blend chemical composition. (I) is a battery separator. The preparation of (I) comprises forming a casting solution containing a poly(aryl ether), a polyimide and at least one solvent, forming a shaped configuration in the form of a flat sheet, a tube, or a hollow fiber from the casting solution, decomposing the polyimide in the shaped configuration into low molecular weight fragments by chemical means, and removing the low molecular weight fragments from the shaped configuration. At least one solvent is partially or completely removed during conveying the shaped configuration.The method further comprises drying the shaped configuration, to remove residual solvent under conditions that substantially preserve the porous structure and the casting solution further contains a non solvent, a poroformer or a filler. The process of solidifying the shaped configuration and decomposing the polyimide in take place concurrently in a common liquid media. The process of decomposing the polyimide and removing the low molecular weight fragments take place concurrently in a common liquid media. The process further comprise a washing step to remove the solvent after solidifying the shaped configuration and before decomposing the polyimide by contacting the shaped configuration with tetramethylammonium hydroxide, primary aliphatic amine and/or secondary aliphatic amine. The microfiltration, ultrafiltration, nanofiltration or gas separation membrane further contain a separation layer formed on top of the flat sheet, tube or hollow fiber surface. (I) is a multilayer article formed from two or more casting solutions that differ in solution chemical composition. The multilayer article contains two or more layers that differ in the average pore size and the layer comprised of the smaller average pore size is supported by or sandwiched between layers with the larger average pore size. In the preparation of (I), the flat sheet is supported by a screen or a permeable cloth. The poly(aryl ether) in the first blend or the at least one additional blend is polyphenylene oxide or polysulfone. EXAMPLE - First, a layer of polysulfone blend film was form on a glass plate with a rim by the solution casting followed by the solvent evaporation at room temperature. The casting solution contained polysulfone (0.6 g) and polyimide (1.4 g) dissolved in chloroform (30 ml). After the solvent in the first layer has been evaporated, a second casting solution contained polysulfone (0.25 g) and polyimide (0.25 g) dissolved in chloroform (15 ml) was cast on top of the first layer followed by solvent evaporation at room temperature. A transparent film with two distinct polymer blend layers was obtained. The thus formed multilayer film was then dried under vacuum at 100 degrees C for 48 hours. The thickness of the multilayer film was 86 micrometers. Both layers exhibit uniform pore size distribution. The average pore diameter in the first bottom layer is about 0.5 micrometer and the average pore diameter in the second top layer is 0.2 micrometers.