Highly selective polymer electrolyte membranes consisting of poly(2-ethyl-2-oxazoline) and Cu(NO(3))(2) for SF(6) separation

Polymer electrolyte membranes consisting of Cu(NO(3))(2) and poly(2-ethyl-2-oxazoline) (POZ) were prepared for SF(6)/N(2) separation. It was anticipated that repulsive forces would be operative between the negative charge of water and the F atoms of SF(6) when Cu(NO(3))(2) in the composite was solvated by water, and that the barrier effect of Cu(2+) ions would be activated. In fact, Cu(NO(3))(2) solvated by water in the POZ membrane was observed to have more higher-order ionic aggregates than free ions or ion pairs, as confirmed by FT-Raman spectroscopy. Thus, when Cu(NO(3))(2) solvated by water was incorporated into the POZ matrix, the N(2)/SF(6) selectivity increased to 28.0 with a N(2) permeance of 11.2 GPU at a POZ/Cu(NO(3))(2) mole ratio of 1:0.7. The coordinative interaction of Cu(NO(3))(2) with the carbonyl group in POZ was confirmed by FT-IR spectroscopy and TGA, and the film thickness of the membrane was determined from SEM analysis.