Evolution of surface chemistry and morphology of hyperbranched polysiloxane polyimides in simulated atomic oxygen environment

Hyperbranched polysiloxane (HBPSi) polyimide membranes were fabricated by copolymerizing amine-functionalized HBPSi and imide monomers. The atomic oxygen (AO) resistance of the resulting polyimides were investigated in simulated AO environment, based on their evolution of surface chemistry and morphology. Results indicated that a silica passivating layer finally formed on the membrane surfaces and, there was a percolation threshold of HBPSi addition to achieve the most desirable AO resistance. This is explained by the formation of a much denser and more connected silica passivating layer in shorter time on the membrane surface at high HBPSi loading upon AO exposure.