Feasibility of thermal crosslinking of polyarylate gas-separation membranes using benzocyclobutene-based monomers

Current literature results suggest that crosslinking may be a useful route to balance the productivity/selectivity tradeoff of polymeric gas-separation membranes. This study explores the use of benzocyclobutene chemistry to thermally crosslink polyarylate membranes based on 1,2-dihydrocyclobutabenzene-3,6-dicarbonyl dichloride (XTA-Cl), fluorene bisphenol (FBP) and 5-t-butyl isophthalic acid dichloride (tBIA). Very high temperatures were required to produce significant crosslinking which also caused significant degradation of the polymers. The result of this heat treatment was small increases in gas permeability coefficients and small decreases in permselectivity; this is opposite to what is typically observed for simple crosslinking. It is concluded that the thermal treatment required for crosslinking is too severe to utilize this approach successfully for polyarylate gas-separation membranes.