Diarylacetylene monomers containing substituted biphenyl (1a-f) and anthryl (1g) groups were synthesized and then polymerized with TaCI5-n-BU4Sn catalyst to produce the corresponding poly(diarylacetylene)s (2a-g). Polymers 2a-f were soluble in common organic solvents such as cyclohexane, toluene, and chloroform. According to thermogravimetric analysis, the onset temperatures of weight loss of the polymers were over 400 degrees C in air, indicating considerably high thermal stability. Free-standing membranes 2a and 2c-e were prepared by the solution casting method. Desilylation of Si-containing membrane 2c was carried out with trifluoroacetic acid to afford 3c. All the polymer membranes, especially those having twisted biphenyl groups, exhibited high gas permeability; for example, their oxygen permeability (P-O2) values ranged from 130 to 1400 barrers. Membrane 2d having two chlorine atoms in the biphenyl group showed the highest gas permeability (P-O2 = 1400 barrers) among the present polymers. (C) 2010 Wiley Periodicals, Inc. J Polym Sci PartA: Polym Chem 48: 861-868, 2010