Liquid crystal polymers and ionomers for membrane applications

[EN] Transport phenomena through polymeric composite membranes depend on several complex factors, involving not only their chemical composition but also their microstructure. Due to the combination of mesomorphic and macromolecular behaviour, thermotropic liquid crystal polymers (LCP) may enhance the transport properties in membranes by improving parameters related to the order, orientation, connectivity and distribution of the different domains arising from phase separation. This paper provides an overview of some existing and potential applications of liquid crystals (LC) in polymeric membranes as effective structure-directing templates or as components providing a dynamic response to external stimuli. The first part is a description of the composition and phase behaviour of LCP containing ionic and ionogenic groups, the so-called liquid crystal ionomers (LCI). The second part is focused on the description of LCP and LCI used in transport applications, such as proton-conducting films in fuel cells, ionic polymer transducers and hydrogels. The paper highlights the relationships between the composition and the LC properties of the materials and their potential as membranes for ionic and solvent transport, with particular attention paid to covalently linked materials prepared by copolymerisation, due to their higher versatility and stability.The author would like to especially thank Professor Amparo Ribes-Greus, from Universitat Politecnica de Valencia, UPV, and Professor Corrie T. Imrie, from the University of Aberdeen, UoA, for their support during the discussion of this work, and also the researchers and students from the research group of Degradation and Recycling of Polymeric Materials in the Institute of Materials Technology (ITM) of UPV. Also acknowledged for their financial support are the Spanish Ministry of Science and Innovation, through the Research Projects ENE2007-67584-C03 and UPOVCE-3E-013, the Ministry of Education and Science for the awarding of two FPU and FPI pre-doctoral grants, and the financial support of the Generalitat Valenciana, through the Grisolia and the ACOMP/2011/189 program. The UPV is also thanked for additional support through the PAID 05-09-4331 programme.Martinez-Felipe, A. (2011). Liquid crystal polymers and ionomers for membrane applications. Liquid Crystals. 38(11-12):1607-1626. https://doi.org/10.1080/02678292.2011.624201160716263811-1