Two novel poly(aryl ether)s, dimethylphenylated poly(ether nitrile) (6H-PEN) and dimethylphenylated poly(ether ether ketone) (6H-PEEK), derived from (3,5-dimethylphenyl)hydroquinone monomer, were synthesized via aromatic nucleophilic substitution polycondensation. They showed high glass transition temperatures and were soluble in common solvents. A comparison of gas permeabilities and permselectivities among methylphenylated (3H-PEEK and 3H-PEN), trifluoromethlyphenylated (3F-PEEK and 3F-PEN), dimethylphenylated (6H-PEEK and 6H-PEN) and 3,5-ditrifluoromethylphenylated (6F-PEEK and 6F-PEN) poly(aryl ether)s were studied. Compared with the methylated polymers, the corresponding fluoromethylated polymers had generally higher permeabilities. The 3F and 6F polymers had combined permeabilities, and C permselectivity properties attractive for O-2/N-2 separation. 6F-PEN exhibited the best gas separation properties for the O-2/N-2, pair, and P(O-2), and P(O-2)/P(N-2) values were 6.6 and 5.9. respectively. Crown Copyright (c) 2005 Published by Elsevier Ltd. All rights reserved.