Asymmetric membranes of phenylated polyphenylene were prepared by wet phase inversion. The polyphenylene (M-n = 62 kDa, PD = 2.3) was prepared by Diels-Alder polymerization of 1,4-bis(tetraphenylcyclopentadienonyl) benzene with 1,4-diethynylbenzene at 180 degrees C. Solvents and non-solvents were experimentally identified and solvent : non-solvent systems were evaluated by the quality of the resulting membranes. Cyclohexanone/n-butanol (88 : 12) as solvent and n-butanol as the non-solvent were found to afford the best asymmetric membranes with minimal defects. Membranes (20-30 mu m thick) from coagulating 11.5 wt % polyphenylene from cyclohexanone/n-butanol in n-butanol baths exhibited 250-300 mm, non-porous skins overlaying 20-30 mu m of open-celled, spongiform structure. Due to a relatively high glass transition temperature of 370 degrees C, the phenylated polyphenylene membranes retained their porosity to 200 degrees C higher than polysulfone asymmetric membranes. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 128: 750-753, 2013