Copolyimide membranes containing both sulfonyl (-SO2) and trifluoromethyl (-CF3) groups, which have high affinity for aromatic hydrocarbons, were prepared and the pervaporation properties of these membranes were investigated for the separation of benzene/cyclohexane mixtures. The 6FDA-DDBT/DABA copolyimides were obtained by polycondensation of 4,4`'hexafluoroisopropylidene dianhydride (6FDA) with dimethyl-3,7-diaminobenzothiophene-5,5`-dioxide (DDBT) and 3,5-diaminobenzoic acid (DABA). In order to prevent excessive swelling effects, the copolyimides were crosslinked with ethylene glycol. With the copolyimides synthesized, sorption and pervaporation experiments were performed for benzene/cyclohexane mixtures at 323 K, 333 K and 351 K. It has been found that all the crosslinked copolyimides showed high separation performances with good chemical and thermal stability. Compared with the noncrosslinked copolyimides, the chemically crosslinked copolyimides exhibited a lower permeation flux and a higher permselectivity. For the most promising membrane meterial, the crosslinked 6FDA-DDBT/DABA (9/1) had a specific permeation flux of 4.94 kgμm/m2h and a separation factor of 17.8 at a feed composition of 60 wt% benzene in cyclohexane at 351 K. Keywords: separation of benzene

방향족 탄화수소에 친화성이 큰 sulfonyl (-SO2)기와 trifluoromethyl (-CF3)기를 함유하는 6FDA-DDBT/DABA 공중합 폴리이미드막을 제조하고 벤젠/싸이클로헥산 혼합액의 분리를 위하여 이들 막의 투과증발 특성을 연구하였다. 공중합 폴리이미드는 4,4`-hexafluoroisopropylidene dianhydride (6FDA)와 dimethyl-3,7-diaminobenzothiophene-5,5`-dioxide (DDBT) 및 3,5-diaminobenzoic acid (DABA)를 축중합하여 합성하였다. 지나친 팽윤 효과를 방지하기 위하여 공중합 폴리이미드는 ethylene glycol과 가교결합시켰다. 합성한 막을 이용하여 323 K, 333 K와 351 K에서 벤젠/싸이클로헥산 혼합액의 수착과 투과증발실험을 행하였다. 가교 폴리이미드는 모두 높은 분리성능과 좋은 화학적 및 열적 안정성을 나타내었으며, 비가교 폴리이미드에 비하여 낮은 투과속도와 높은 선택도를 나타내었다. 가교 6FDA-DDBT/DABA(9/1)막은 351 K에서 벤젠농도가 60 wt%인 싸이클로헥산과의 혼합용액에서 4.94 kgμm/m2h의 비투과속도와 17.8의 분리계수를 나타내었다.