In recent years superglassy polymers exhibiting intrinsic microporosity established a new perspective for a number of applications, especially for gas separation membranes as these polymers combine extremely high permeabilities with attractive selectivities. The essential factor governing the structure formation in the solid film or layer is either a contorted rigid backbone (polymers of intrinsic microporosity - PIMs) or extremely bulky side groups (polynorbornenes and polytricyclonenenes).<br/>For a deeper understanding of both types of such high-performance polymers for gas separation membranes and their further development broadband dielectric spectroscopy (BDS) can provide a substantial contribution. BDS addresses molecular relaxations characterizing the dynamics of the solid polymer as a major factor determining the gas transport properties but also the physical aging behavior which is an essential issue for such polymers.<br/>BDS is applied on PIMs where fluctuations of molecular dipoles connected to the backbone can be directly monitored. Furthermore, also polynorbornenes were investigated which carry no dipole moment in their repeat unit - the high resolution of modern equipment allows for the detailed analysis also for very small dielectric losses originating from partially oxidized moieties or marginal catalyst residues.<br/>Additionally, from interfacial polarization phenomena, such as Maxwell-Wagner-Sillars (MWS) polarization due to blocking of charge carriers at internal interfacial boundaries on a mesoscopic length scale, valuable information on the intrinsic microporosity and its changes induced by physical aging can be obtained.<br/>Finally, also conductivity can be characterized in detail in such polymeric systems revealing contributions of interactions of aromatic moieties (π-π-stacking) or the drift motion of charge carriers. These features also determine the structure formation in the solid state.

Characterization of high-performance membrane polymers for gas separation using broadband dielectric spectroscopy

2019 Spring National Meeting

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