Microporous Networks of High-Performance Polymers: Elastic Deformations and Gas Sorption Properties

Aromatic poly(imide) and poly(amide) networks have been synthesized using a tetrafunctionalized spirobifluorene unit as cross-linker and packing inhibitor. The poly(imide) network exhibits intrinsic microporosity and consequently high surface areas of about 1000 m2/g from nitrogen sorption, while the poly(amide) network does not exhibit N2-accessible pores and consequently no detectable surface area. Combined gas sorption and small-angle X-ray scattering analysis reveals the particularities for the evaluation of pore volume, pore size distribution, and surface areas of such soft microporous frameworks. Besides surface adsorption, pronounced elastic deformation is observed during increasing gas pressures, related to inner gas binding sites also known from the "dual-mode sorption" process of classical polymer membranes. The networks have furthermore been tested as hydrogen storage materials and show high hydrogen uptakes at low pressures. Surprisingly, also the polyamide network stored remarkable amounts of hydrogen.