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Membranes, Aromatic Ionomer, Structure

Many research studies have focused on improving the nanophase-separated structures between the hydrophilic and hydrophobic units to increase the proton conductivity of the aromatic ionomers under low RH. In this section, recent approaches to improve the membrane properties, especially the proton conductivity, which is usually the first characteristic considered when evaluating membranes for fuel cells, and morphology will be discussed as follows (1) multiblock SPES copolymers, (2) locally and densely SPES, (3) SPES with high lEC values and high free volume, (4) SPES with pendant perfluoroalkyl sulfonic acids, (5) cross-linked SPES, and (6) thermally annealed SPESs. [Pg.157]

Despite its higher lEC values, the proton conductivity of the membranes was lower than that of the Nafion membrane. The authors concluded that acidity was a crucial factor to determine the proton conducting properties. However, other structural factors, such as the hydrophobicity and flexibility of the main chain, would have to be optimized for further improving the proton conductivity of the aromatic ionomer membranes [51]. On the other hand, Ueda and coworkers reported a novel PES containing binaphthyl units with pendant perfluoroalkyl sulfonic acids (BNSH-PSA) for PEM [52]. The BNSH-PSA (1EC=1.91 meq./g) was prepared by the aromatic nucleophilic substitution reaction of l,T-binaphthyl-4,4 -diol and 4,4 -dichlorodiphe-nylsulfone, followed by bromination with bromine, and then the Ullmann coupling reaction with PSA-K (Scheme 4.19). [Pg.182]

The sensitivity to hydrolysis is a key issue in many applications. The ester bond in 4GT-PTMO copolymers is sensitive to hydrolysis however, it is fairly protected since most of the ester is contained in a crystalline structure. The addition of a small amount (1-2%) of a hindered aromatic polycarbodiimide substantially increases the lifetime of this material in the presence of hot water or steam (Brown et al., 1974). Polyurethanes are susceptible to hydrolytic attack, especially those with polyester soft segments. However, polyester soft segment polyurethanes are generally more resistant to oils, organic solvents, and thermal degradation. lonomers will swell when exposed to water in fact, a commercial hydrated perfluorosulfonic ionomer (Nation) is used as a membrane separator in chlor-alkali cells. Styrene-diene copolymers and polyolefin TPEs are insensitive to water. [Pg.627]

These findings are, more or less, applicable to the other aromatic hydrocarbon ionomers and useful to design the higher-order structure and properties of ionomer membranes. [Pg.1026]

This chapter is a review focussed on the development of ionomers based on aromatic polysulfones for their application as Polymer Electrolyte Membrane (PEM) in Proton Exchange Membrane Fuel Cells (PEMFC) or in Direct Methanol Fuel Cells (DMFC). Different types of synthesis routes have been discussed in this chapter in order to obtain ionomers based on polysulfones with variation in structural designs. Special attention is given to the impact of the structural design of the ionomer on various properties such as membrane morphology, thermo-mechanical stability and protonic conductivity of the membranes for their utilization as PEMs. [Pg.81]


See other pages where Membranes, Aromatic Ionomer, Structure is mentioned: [Pg.1025]    [Pg.182]    [Pg.391]    [Pg.73]    [Pg.82]    [Pg.530]    [Pg.102]    [Pg.102]    [Pg.65]    [Pg.566]    [Pg.477]    [Pg.65]    [Pg.225]    [Pg.102]    [Pg.3038]    [Pg.1027]    [Pg.1028]    [Pg.188]    [Pg.199]    [Pg.588]    [Pg.238]    [Pg.361]   
See also in sourсe #XX -- [ Pg.375 , Pg.378 ]




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Aromatic Ionomers

Aromatic structures

Aromatics structure

Ionomers structure

Membrane ionomers

Membranes structure

Membranes structured

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