Two novel aromatic diamines 3

5-diaminobenzophenone (PDA) and 4-(trifluoromethyl)phenyl 3

5-diaminobenzoate (FPDA) were mixed separately with 4

4'-diaminodiphenyl ether (ODA) and 3

5-diaminebenzoic acid (DABA) with different ratios

and then copolymerized separately with 4

4'-oxydiphthalic anhydride (ODPA)

3

3'

4

4'-benzophenonetetracarboxylic dianhydride (BTDA) and 4

4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) to give poly(amic acid)s

which were converted into cross-linked polyimides (PIs) with ethylene glycol (EG) by thermal imidization.The structures of these series of PIs were characterized by FT-IR

NMR and GPC.The effect of side-chain content on the thermal stability was investigated by DSC and TGA.The effects of the fluorine group on the properties and separation performance of side-chain polyimides were investigated.The membranes of polyimide obtained were employed in pervaporation separation of benzene/cyclohexane mixtures.The two side-chain polyimide membranes containing 6FDA have an optimal separation efficiency in terms of both flux and separation factor.The cross-linked 6FDA-FPDA/ODA/DABA (1:7:2) membranes show the most promising separation performance with a flux of 9.84 kg·μm·m-2·h-1 and separation factor of 6.1 for benzene/cyclohexane (50/50

mass ratio) at 50℃.