Poly(2,6-dimethyl-1,4-phenylene oxide) blends with a poly(arylene ether ketone) for gas separation membranes

Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) is utilized for gas separation membranes. It has a relatively high free volume with high gas permeabilities but suffers from low selectivities. PPO polymers with Mn's from 2000 to 22,000 g/mole were synthesized and blended with a poly(arylene ether ketone) derived from bisphenol A and difluorobenzophenone (BPA-PAEK). DSC showed that the blends with all but the lowest molecular weight PPO had two Tg's, thus suggesting that two phases were present. The ketone carbon and benzylic methyl groups on the BPA-PAEK and the PPO polymers crosslinked upon exposure to UV light. The gel fractions after UV exposure were high and the tensile properties were similar to the PPO control polymer that is currently used as a gas separation membrane. The crosslinked blends had improved gas selectivities over their linear counterparts. The 90/10 wt/wt 22k PPO/BPA PAEK crosslinked blends gained the most O2/N2 selectivity and maintained a high permeability.