Molecular Weight and Gas Separation Performance of Polyimide Membrane: Insight into Role of Imidization Route

Various methods have been explored to improve the gas separation performance of polyimide membrane for more viable industrial commercialization. Generally, polyimide membrane can be synthesized via two different methods: chemical imidization and thermal imidization routes. Due to the markedly different membrane synthesis conditions, the influence of imidization methods on the gas transport properties of resulting membrane is worthy of investigation. The polyimide produced from two imidization methods was characterized for its molecular weight. In overall, the molecular weight of thermally imidized polyimide was higher than that of chemically imidized one except ODPA-6FpDA:DABA as it was prone to depropagation at high temperature. It was observed that the chemically imidized ODPA-6FpDA:DABA membrane possessed better gas separation performance than the thermally imidized counterpart. In particular, it showed 12 times higher CO2 permeability (19.21 Barrer) with CO2/N2 selectivity of 5. After crosslinking, the CO2/N2 selectivity of the polyimide membrane was further improved to 11.8 at 6 bar of permeation pressure.