Development of Polyimide Polymers membranes for Pervaporation and Vapor-Permeation of Hydrocarbon Mixtures.

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The crosslinked membranes of the phosphorylated polymides displayd higher pervaporation (PV) performance with excellent durability toward aromatic/non-aromatic hydrocarbon mixtures, compared with the base polymide and its homolog membranes, because of the higher solubility selectivity due to affinity of the phosphonate groups to the aromatic hydrocarbons.Polymides from thianthrene-2,3,7,8-tetracarboxylic dianhydride-5,5-10,10-tetraoxide and diamines were synthesized and the investigation of their PV properties are in progress. Copolyimides from 2,2'-diethynylbenzidine were synthesized. The crosslinking based on the ethynyl groups enhanced the PV performance due to the increased diffusivity selectivity. The addition of tetracyanoethylene was also effective for the improvement of the PV performance.Carbon molecular sieve membranes wer prepared by pyrolyzing polyimide and polypyrrolone membranes at 500-700 ﾟC in N2. They displayd high performance for gas separation such as propylene/propane.Poly (glycidyl methacrylate) grafted membranes were prepared using porous high density polyethylene films as substrate. The membranes prepared by the homogeneous both-side plasma treatment and under the mild polymerization conditions displayd the highest PV performance.