Synthesis and Gas Permeability of Polynorbornene Dicarboximides Bearing Sulfonyl Moieties

This work reports on the synthesis and ring-opening metathesis polymerization (ROMP) of two novel homologous sulfonyl-containing norbornene dicarboximide monomers, specifically, <i>N</i>-4-(trifluoromethylsulfonyl)phenyl-norbornene-5,6-dicarboximide (<b>1a</b>) and <i>N</i>-4-(trifluoromethylsulfonyl)phenyl-7-oxanorbornene-5,6-dicarboximide (<b>1b</b>) using the Grubbs 2nd generation catalyst (<b>I</b>). The polymers are thoroughly characterized by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), thermomechanical analysis (TMA), thermogravimetric analysis (TGA), atomic force microscopy (AFM), and X-ray diffraction (XRD), among other techniques. A comparative study of gas transport in membranes based on these ROMP-prepared polymers is performed and the gases studied are hydrogen, oxygen, nitrogen, carbon dioxide, methane, ethylene and propylene. It is found that the presence of sulfonyl pendant groups in the polymer backbone increases the gas permselectivity in slight detriment of the gas permeability compared to a polynorbornene dicarboximide lacking sulfonyl groups. The membrane of the sulfonyl-containing polymer with an oxygen heteroatom in the cyclopentane ring, <b>2b</b>, is also found to have one of the largest permselectivity coefficients reported to date for the separation of H₂/C₃H₆ in glassy polynorbornene dicarboximides.