Gas transport coefficients of phthalide-containing high-T<inf>g</inf> glassy polymers determined by gas-flux and NMR measurements

Abstract

The synthesis of three aromatic polymers containing phthalide cardo groups having high inherent viscosities is described. Polyimides PIC-6F and PIC-TB were prepared from a cardo diamine and two different dianhydrides, and poly(phthalidylidenearylene) (PPDAr) was prepared by a precipitative Friedel-Crafts homopolycondensation of 3-(4-biphenylyl)-3-chlorophthalide. All polymers presented high glass transition temperatures varying between 600 and 690 K. Dense membranes prepared by casting from N,N-dimethylacetamide solutions exhibited good mechanical properties and decomposition temperatures over 770 K under a N<inf>2</inf> atmosphere. Results of gas transport measurements of O<inf>2</inf>, N<inf>2</inf>, and CO<inf>2</inf> were comparatively analyzed based on the chemical structure of the polymers. Additionally, the solubility, diffusion, and permeability coefficients of [¹³C]O<inf>2</inf> in these membranes were determined by ¹³C NMR spectroscopy and pulsed-field gradient NMR measurements, and the results were in good agreement with those determined with pressure-driven measurements. It was found that membranes of PPDAr exhibited the highest permeability and CO<inf>2</inf>/N<inf>2</inf> and CO<inf>2</inf>/O<inf>2</inf> permselectivities.