The dependence of hydrocarbon gas transport behaviour on the liquid crystalline (LC) and isotropic state of different liquid crystalline side chain elastometer membranes (LCSCE‐membranes) is investigated with respect to the LC‐phase structure of the membranes and the molecular shape of the gas molecules.—A distinct change of the transport behaviour at the phase transformation from the smectic to the nematic and from the nematic to the isotropic state is observed. Additionally, an odd‐even effect is detected determined by the spacer length of the mesogenic moieties at a temperature range a little above the phase transformation temperature from the LC‐ to the isotropic state. It is assumed that this odd‐even effect correlates with the stress temperature dependence of the LCSCE‐samples. An enhanced selectivity for linear shaped gases compared to spherical shaped gases occurs in a macroscopic ordered sample.—For these experiments the accuracy of the transport coefficient determination by a transport process through membranes is analysed with respect to the geometrical arrangement of the developed experimental apparatus. The experimental method of determing transport coefficients, already described by R. A. Pasternack, is discussed and further developed.—The LCSCE‐membranes are synthesized by adding a mesogenic side chain to a polymethylhydrogensiloxane network.

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