A complete series of aliphatic aromatic copolyimides has been synthesized. In this case all the samples had the same structure, BKDA-PEO6000-ODA, but different percentage of PEO in the final polymer. These copolymers have been thermally treated and characterized by several techniques. A direct relationship between temperature of treatment and both phase segregation and permeability improvement has been demonstrated.
Results show that the permeability is higher when higher the PEO content is, but otherwise the selectivity does not follow the same trend. Notable is the case of the CO2/N2 couple of gases that show selectivity-versus-permeability very near the upper bound of Robeson especially when permeation is done at 50 °C.
The Maxwell model has been applied to carry out the prediction of permeability (for CO2, CH4, O2 and N2) and it has been found that depending on the percentage of amorphous PEO in the polymer, the model reproduces well the experimental tendency.
