Gas Permeation Property of Polyimide-Poly(ethylene glycol) Copolymer Membranes

The CO₂ removal process using polymeric membranes has been developed and received a great attention because of global warming. However, polymeric membranes still have low permeability and selectivity. Many researchers have been studied to resolve this weakness. Among various polymer membranes, polysulfone and polyimide have several advantages such as good chemical resistance, mechanical properties and gas separation performance. These kinds of glassy polymers are affected by diffusivity-selectivity. The high diffusivity of glassy polymer can be achieved easily by control of the fractional free volume (FFV) which relates to rotational and flexural mobility of polymer chain. Polymer membranes introduced fluorene bulky groups into polymer backbone showed high FFV and diffusivity. Permeability of rubbery polymer membranes such as poly(ethylene glycol) (PEG) influenced by solubility-selectivity. Rubbery polymer membranes have high CO₂ permeability and high polar/nonpolar gas selectivity. In this work, we synthesized fluorene-based polysulfone-PEG and polyimide-PEG random copolymer and prepared copolymer membranes. Molecular weight and mole percent of PEG were controlled to investigate the effect of PEG. Finally, thermal properties, fractional free volume (FFV) and gas permeability PEG-containing random copolymer membranes were investigated.