SYNTHESIS AND CHARACTERIZATION OF POLYIMIDES WITH PENDANT PHOSPHONATEESTER GROUPS

A polyimide from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 2,4,6-trimethyl-1,3-phenylenediamine (TrMPD). which has less effic ient packing of polymer chains and displays very high gas permeability , was methyl-brominated and then phosphorylated by the reaction of -CH 2Br with triethyl phosphite. The degree of phosphorylation upto 200% ( two phosphonate ester groups per repeating unit) was achieved. Phospho rylation increased the sorption amount of benzene but decreased that o f cyclohexane. Phosphorylated polyimide membranes were crosslinked the rmally and/or with diamine. The amine-crosslinked membranes with P con tent of 5.9-8.3 wt% have high performance of pervaporation of benzene- cyclohexane mixtures; for example, specific permeation flux of 10 kg m u m m(-2) h(-1) and separation factor of 15 at 343 K and benzene compo sition in feed of 50 wt%.