Transport properties of crosslinkable polyimide blends

The use of polymeric membranes for separation of chemically aggressive media, or at elevated temperatures, has been limited by membrane availability. While a number of polymers are both resistant to chemical dissolution and thermally stable to over 300 degrees C, none has been shown to be simultaneously capable of the selective transport of gases at high rates. The research reported here analyzes the influence of solid-state crosslinking of polyimides to achieve this unique combination of properties. Polyimide blends consisting of an inert polymer base with a diacetylene-functionalized additive were prepared and the properties evaluated before and after crosslinking by thermal annealing. Crosslinking rendered the resultant polymers insoluble in what were previously solvents, but had no measurable influence on gas permeabilities or selectivities. The permeability/permselectivity of these new crosslinked polyimide bleeds are competitive with the best known polymers. Moreover, the combined ease of processing and resultant stability are unmatched.