A series of hydrogen-bonded cardo poly(aryl ether ketone) copolymers were prepared by polymerization from a mixture of phenolphthalein (PPH) and 3,3'-bis(4-hydroxyphenyl)isobenzopyrrolidone (HPP) with equivalent molar bis(4-nitrophenyl) ketone. The gas permeabilities of H-2, O-2, and N-2 through copolymer membranes were examined over a temperature range of 30-100 degrees C. In comparison with bisphenol A polysulfone (PSF), all the homo- and copolymers exhibited similar H-2 permeability coefficients, but H-2/N-2 selectivity coefficients were more than twice as high as that of PSF. Of interest was the observation that, different from previous other copolymers, the gas permeability in this study exhibited a sigmoid dependency on comonomer composition, and the variation amplitude of gas permeability coefficients between wave trough (40 mol % HPP) and wave crest (60 mol % HPP) was reduced with increased temperature. This peculiar phenomenon was interpreted according to polymeric structural factors, including free volume, interchain distance, glass transition, secondary transition, and the effect of temperature on interchain hydrogen bonds.