The polymer electrolyte membranes based on Proton Conducting Ionic liquids (PCIL) are very promising systems for the high temperature-PEMFC technology owing to their good ionic conductivity and stability at temperatures above 100oC. The objective of this thesis work is to achieve a profound study on the evolution of morphology and consequent functional properties of the PCIL based polymer electrolyte membranes in function of: i). concentration of the PCIL, ii). the method of elaboration and iii). chemical structure of the PCIL. To demonstrate the potential of these membranes in HT-PEMFC, preliminary tests have been carried out in the fuel cell stack and degradation phenomena associated with PCILs and membranes in the presence of hydrogen peroxide have been studied. The first part of this work is focused on the characterization of Nafion® membranes neutralized with triethylamine (Nafion-TEA) and swollen with triethylammonium Triflate (TFTEA). It has been shown that Nafion-TEA exhibits a single layer string-like organization of inter-digited Triethylammonium cations at the hydrophobic-hydrophilic interface when in anhydrous state. The introduction of TFTEA into Nafion-TEA membrane does not destroy its nano-structuration but significantly boosts the anhydrous ionic conductivity and hydrophilicity of the system. The second part of this work has permitted us to establish the fact that doped membranes prepared by casting method have better organization and better thermo-mechanical properties compared to those obtained by swelling method. Third part of this work focuses on the impact of the chemical nature of the PCIL on the morphology and functional properties of Nafion-TEA membranes. It has been demonstrated that the PCILs with long perfluorinated chain length do not modify the nano-structuration of Nafion-TEA membranes at all. This has a strong impact on the ion-conducting, water-sorption and thermo-mechanical properties of the membrane. In the last part, aromatic ionomers were synthesized in order to replace Nafion-TEA in such PCIL based system. Despite the similar structure of the side chain of the synthesized aromatic ionomers and Nafion®, the membranes based on aromatic ionomers and TFTEA do not present any nano-structuration. Moreover, the plasticizing effect of TFTEA is more noticeable in the case of aromatic ionomers probably due to a random distribution functions in the ionic polymer membrane.
Nano-structured polymer electrolytes based on ionic liquids for high temperature-pemfc