TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Solvents: The solvent medium comprises a halogenated phenolic solvent, preferably 4-chloro-3-methyl-phenol, 4-chloro-2-methyl-phenol, 2,4-dichloro-6-methyl-phenol, 2,4-dichloro-phenol, 2,6-dichloro-phenol, 4-chloro-phenol, 2-chloro-phenol, o-cresol, m-cresol, p-cresol, 4-methoxy-phenol, catechol, benzoquinone, 2,3-xylenol, 2,6-xylenol and/or resorcinol. The solvent medium comprises primary and secondary solvents. The primary solvent is chosen from 4-chloro-3-methyl-phenol, 4-chloro-2-methyl-phenol, 2,4-dichloro-6-methyl-phenol, 2,4-dichloro-phenol, 2,6-dichloro-phenol, 4-chloro-phenol and/or 2-chloro-phenol. The secondary solvent is chosen from o-cresol, m-cresol, p-cresol, 4-methoxy-phenol, catechol, benzoquinone, 2,3-xylenol, 2,6-xylenol and/or resorcinol. The solvent medium comprises 50 wt.pts of 4-chloro-2-methyl-phenol and 50 wt.pts of p-cresol. The solvent medium further comprises a co-solvent. The solvent having melting point of greater than 20degreesC is chosen from 4-chloro-3-methyl-phenol, 4-chloro-2-methyl-phenol, 2,4-dichloro-6-methyl-phenol, 2,4-dichloro-phenol, 2,6-dichloro-phenol, 4-chloro-phenol and/or 2-chloro-phenol, preferably 4-chloro-2-methyl-phenol. The co-solvent is chosen from o-cresol, m-cresol, p-cresol, 4-methoxy-phenol, catechol, benzoquinone, 2,3-xylenol, 2,6-xylenol and/or resorcinol, preferably cresol or p-cresol.    TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The polymer is at least partially crystalline. The polymer comprises polyketone, polyether ketone, polyarylene ether ketone ketone, polyimide, polyetherimide or polyphenylene sulfide, preferably polyarylene ether ketone ketone or polyimide. The polyimide comprises structural units derived from benzophenone-3,3',4,4'-tetracarboxylic dianhydride and at least one diamine chosen from 1,4-diaminobenzene, m-phenylenediamine and/or p-phenylenediamine. The polymer comprises polyetherimide comprising structural units derived from at least one anhydride chosen from oxydiphthalic anhydride and/or bisphenol-A diphthalic anhydride and at least one diamine chosen from 1,4-diaminobenzene, m-phenylenediamine and/or p-phenylenediamine. Preferred Method: The process for producing polymeric membrane involves casting a thin film from the polymer solution. The polymer solution is contacted with a coagulating bath comprising a non-solvent for the polymer. The solvent of the solvent medium is removed from the polymer solution. EXAMPLE - Para-cresol (in g) (40) was added to 100 ml flask. The flask was heated, and oxydiphthalic anhydride-based polyetherimide (2) was added, and the temperature was increased to 140degreesC. The polyetherimide pellets remained intact at 140degreesC under vigorous stirring. Subsequently, 4-chloro-2-methyl phenol (40) was added to a flask. The flask was heated to 120degreesC, and the pellets were added to the flask and stirred vigorously. A homogeneous solution of the polymer in solvent was obtained. Para-cresol (28.9) was added to the solution, and the temperature was maintained at 120degreesC. Additional polyetherimide powder was added to the flask, and a polymeric solution was obtained. The polymeric solution was cooled to room temperature, and cast on a glass plate. The formed wet film was quenched to produce a porous polyimide membrane. The membrane had excellent solvent resistance.