Synthesis and gas permeation properties of novel spirobisindane-based polyimides of intrinsic microporosity

Three novel polyimides (PIM-PIs) with characteristics similar to a polymer of intrinsic microporosity (PIM) were prepared by the reactions of a novel spirobisindane-based dianhydride with appropriate aromatic diamines. A polymerisation procedure via in situ ester precursor formation provided PIM-PIs with very high molar masses. The gas permeation parameters (permeability (P), diffusion (D) and solubility (S) coefficients) were determined for these polymers. These PIM-PIs exhibit both high apparent surface areas and high gas permeability coefficients, greater than those of most polyimides studied so far and only slightly smaller than the permeability coefficients of the archetypal polymer of intrinsic microporosity, PIM-1. Treatment of the films with alcohols results in significant increases the P values, just as has been noted for PIM-1. This enhancement is caused by an increase of the diffusion coefficients, while the solubility coefficients are much less sensitive to this treatment. However, PIM-PIs are distinguished by extremely high gas solubility coefficients a property, which is characteristic to all PIMs.