Influence of the Phase Structure on the Gas Transport Behaviour Through Liquid Crystalline Side Chain Elastomer Membranes

Abstract

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.

Sorption Properties of Functionalized Liquid Crystalline Networks

“…The diffusion coefficients for all of the samples were found in the range of 10 −9 cm 2 /s. This is in good agreement with those measured by other authors through mesogenic materials. ,, …”

“…Many studies elucidate relationships between polymer structures, such as the free volume, polymer chain packing, helical structure and intersegmental distance, and their gas transport properties. Among them, the use of a thermotropic liquid-crystalline polymer (TLCP) as the membrane – or a component of a membrane for gas permeation experiments seems, due to their specific properties, to be of special interest . For these materials, permeabilities mainly depend on the state of the membrane (below or above the glass temperature, in a liquid-crystalline state or not, and so forth) and the structure of the mesogenic groups (spacer length, chemical structure, and so forth).…”

Investigation of the Thermal and Morphological Behavior of Liquid-Crystalline Acetylene Homo- and Copolymers

“…Furthermore, the synthesis of block copolymers is possible as well. 24 With respect to the interesting features of both polyacetylenes [25][26][27][28][29][30][31][32][33][34][35][36] and liquid-crystalline polymers [37][38][39][40][41][42][43][44][45][46][47][48] in membrane processes for gas separation, these new materials are of fundamental interest not only for the investigation of structure-property relationships but also for their potential application in this field.…”

Polymerization of the Organized Phases of Polyelectrolyte−Surfactant Complexes

“…The ability of swelling under structural preservation gives the possibility to tune the material properties of those highly anisotropic networks, and the residual reactive groups enable further postmodification. The behavior and potential applications of the present class of polymer mesostructures have to be seen in strict analogy with polymerized smectic liquid-crystalline networks, where unusual tensorial mechanical properties, 27 piezo- 28 and pyroelectricity 29 as well as switchable gas diffusion, 30 have been examined. Extending the present materials, it is also possible to locate and couple other materials properties within the polyelectrolyte phase (such as conductivity), which may lead to further development of smart functional materials.…”