States of water in proton exchange membranes: Part A - Influence of chemical structure and composition

Abstract

Disulfonated poly(arylene ether) and polyimide copolymers can phase separate to form nano-scale hydrophilic and hydrophobic domain morphology. Water in these domains has been assigned to three different states, tightly bound, loosely bound and free water. The states of water were characterized using DSC, NMR relaxation and TGA. The chemical structures of the proton exchange membranes were varied in chemical composition, microstructure (random and block) and also regarding functional sulfonic acid groups fixed to the polymer backbones. A strong dependence of the types of water on the ion content and morphology was observed. For the random copolymers, the formation of free water in the system occurs after reaching a certain ion content.

Perfluorosulfonyl Imide versus Perfluorosulfonic Acid Ionomers in Proton‐Exchange Membrane Fuel Cells at Low Relative Humidity

“…The proton conductivity of ionomers generally rises with the hydration degree as a consequence of (i) the reduction of confinement effects at the nanoscale, (ii) the increase of connectivity, and (iii) the development of structural diffusion . The proton conductivity as a function of RH at 25 °C is presented on Figure c for Si X / Y (red) and In X / Y (blue).…”

“…The proton conductivity of ionomers generallyr ises with the hydration degree as ac onsequence of (i)the reduction of confinemente ffects at the nanoscale, [17,18,[43][44][45] (ii)the increase of connectivity, [5,46] and (iii)the development of structural diffusion. [18,22,[47][48][49][50][51] The proton conductivity as af unction of RH at 25 8Ci sp resented on Figure 3c for Si X/Y (red) and In X/Y (blue). The conductivities of Si X/Y compounds are much lower than those of the In X/Y over the entire hydration range.…”

Synthesis and Characterization of Organosoluble, Thermal Stable and Hydrophobic Polyimides Derived from 4-(4-(1-pyrrolidinyl)phenyl)-2,6-bis(4-(4-aminophenoxy)phenyl)pyridine

“…Aromatic polyimides (PIs) are a class of macromolecular high-performance polymers possessing the imide rings and aromatic groups in the main chains [1,2,3,4,5]. They have been applied in the fields of electronic devices, microelectronic packaging, gas separation, optoelectronic, and automobile industries due to their unique heat resistance, superior chemical stability, special physical, and their mechanical properties [6,7,8,9,10,11,12]. However, although possessing the superior comprehensive properties mentioned above, most of these polymers show some serious drawbacks.…”

Preparation and Biodegradation of Nanocellulose Reinforced Polyvinyl Alcohol Blend Films in Bioenvironmental Media

“…Rate of water solubility for the pure PVOH was slower than the NCC modified PVOH composites. The 30/70 weight percent of PVOH/NCC showed higher solubility rate, which indicated 60% for both of in water and acidic media [14]. For other weight ratio of PVOH/NCC the solubility rate in water is higher than in acid because the concentration of acid is higher than of water.…”