Molecular mobility in high‐performance polynorbornenes: A combined broadband dielectric, advanced calorimetry, and neutron scattering investigation

The molecular dynamics of two addition type polynorbornenes, exo‐PNBSi and PTCNSi1, bearing microporosity has been investigated by broadband dielectric spectroscopy, fast scanning calorimetry, and neutron scattering. Both polymers have the same side groups but different backbones. Due to their favorable transport properties, these polymers have potential applications in separation membranes for gases. It is established in literature that molecular fluctuations are important for the diffusion of small molecules through polymers. For exo‐PNBSi, two dielectric processes are observed, which are assigned to Maxwell/Wagner/Sillars (MWS) process due to blocking of charge carriers at internal voids or pore walls. For PTCNSi1, one MWS‐polarization process is found. This points to a bimodal pore‐size distribution for exo‐PNBSi. A glass transition for exo‐PNBSi and for PTCNSi1 could be evidenced for the first time using fast scanning calorimetry. For Tg and the corresponding apparent activation energy, higher values were found for PTCNSi1 compared to exo‐PNBSi. For both polymers, the neutron scattering data reveal one relaxation process. This process is mainly assigned to methyl group rotation probably overlayed by carbon–carbon torsional fluctuations. Chemical structure, dielectric spectra, heat flow and time dependent scattering function for exo‐PNBSi