Ionomer formation sulfonated

Ionomer formation 150 to 400 Depending on cations in sulfonated ionomers [83-85] [87-90]... 

Sulfonation is very useful chemical modification of polymer, as it induces high polarity in the polymer changing its chemical as well as physical properties. Sulfonated polymers are also important precursors for ionomer formation [75]. There are reports of sulfonation of ethylene-propylene diene terpolymer (EPDM) [76, 77], polyarylene-ether-sulfone [78], polyaromatic ether ketone [79], polyether ether ketone (PEEK) [80], styrene-ethylene-butylene-styrene block copolymer, (SEBS) [81]. Poly [bis(3-methyl phenoxy) phosphozene] [82], Sulfonated polymers show a distinct peak at 1176 cm"1 due to stretching vibration of 0=S=0 in the -S03H group. Another peak appears at 881 cm 1 due to stretching vibration of S-OH bond. However, the position of different vibrational bands due to sulfonation depends on the nature of the cations as well as types of solvents [75, 76]. 

Sulfonated EPDMs are formulated to form a number of rubbery products including adhesives for footwear, garden hoses, and in the formation of calendered sheets. Perfluori-nated ionomers marketed as Nation (DuPont) are used for membrane applications including chemical-processing separations, spent-acid regeneration, electrochemical fuel cells, ion-selective separations, electrodialysis, and in the production of chlorine. It is also employed as a solid -state catalyst in chemical synthesis and processing. lonomers are also used in blends with other polymers. 

Ionomers are polymers which contain up to about 10% mole percent of ionic group [83-85]. Ionomers show interesting properties because of the presence of different interactions which include hydrogen bonding, formation of charge transfer complexes and ion-ion interactions. Polymers with carboxylic or sulfonic acid groups in its backbone on neutralisation with zinc, sodium or other metal salts form ionic aggregates. 

IR spectroscopy can be used to characterise the formation of ionomers by studying the environment of the anions [85, 86]. Risen and co-workers [87, 88] used far-IR spectra (150 to 400 cm"1) to demonstrate the sensitivity of low frequency vibrations to the anions and cations and the degree of cluster formation in ionomers. For example, styrene sulfonic acid ionomers with Na+ cation shows absorption bands at 220 cm 1, whereas the Cs+ cation shows bands at 100 cm 1. 

Mixed anionic (sulfonated - carboxylated) ionomers [81] were prepared by sulfonation of maleated block-copoly (styrene/ethylene-butylene/styrene) (m-SEBS) by acetyl sulfate, followed by neutralisation of the sulfonated maleated product, leading to the formation of a new block copolymer ionomer based on both carboxylate and sulfonate anions according to Scheme 4.6. FT-IR spectra confirm the presence of both carboxylated and sulfonate ions (Figure 4.9). 

In this work we used polystyrene-based ionomers.-Since there is no crystallinity in this type of ionomer, only the effect of ionic interactions has been observed. Eisenberg et al. reported that for styrene-methacrylic acid ionomers, the position of the high inflection point in the stress relaxation master curve could be approximately predicted from the classical theory of rubber elasticity, assuming that each ion pah-acts as a crosslink up to ca. 6 mol %. Above 6 mol %, the deviation of data points from the calculated curve is very large. For sulfonated polystyrene ionomers, the inflection point in stress relaxation master curves and the rubbery plateau region in dynamic mechanical data seemed to follow the classical rubber theory at low ion content. Therefore, it is generally concluded that polystyrene-based ionomers with low ion content show a crosslinking effect due to multiplet formation. More... 

Novel sulfonated and carboxylated ionomers having "blocky" structures were synthesized via two completely different methods. Sulfonated ionomers were prepared by a fairly complex emulsion copolymerization of n-butyl acrylate and sulfonated styrene (Na or K salt) using a water soluble initiator system. Carboxylated ionomers were obtained by the hydrolysis of styrene-isobutyl-methacrylate block copolymers which have been produced by carefully controlled living anionic polymerization. Characterization of these materials showed the formation of novel ionomeric structures with dramatic improvements in the modulus-temperature behavior and also, in some cases, the stress-strain properties. However no change was observed in the glass transition temperature (DSC) of the ionomers when compared with their non-ionic counterparts, which is a strong indication of the formation of blocky structures. 

Interestingly, ionic cluster formation was observed in the case of another aromatic ionomer, the Na salt of sulfonated polyether-ketone47,67. 

Ueda and his co workers of Tokyo Institute of Technology confirmed this strategy with their sulfonated poly(arylene ether sulfone)s (Fig. 7.22) [59-61]. Their polymers contain highly sulfonated moieties (up to ten sulfonic acid groups per repeating unit) randomly distributed in the main chains. Large difference in the polarity between highly sulfonated units and hydrophobic units caused the formation of defined phase-separated structures and well-coimected proton pathways. The proton conductivity of the ionomer membrane with lEC = 2.38 meq/g was comparable to that of Nation 117 at > 30% RH, 80°C. 

Telfah A, Majer G, Kreuer KD, Schuster M, Maier J (2010) Formation and mobility of protonic charge carriers in methyl sulfonic acid-water mixtures a model for sulfonic acid based ionomers at low degree of hydration. Solid State Ionics 181 461 65... 

These systems are based on ionomers, i.e., polymers containing ionic groups, mainly anions such as sulfonic or carboxylic groups. They are neutralized with bases to form salts, which contribute to hydrophilicity (formation of bonds with water), and formation of stable dispersions of polymers in water. After drying, a film on the applied surface is formed. Orientation of molecules, hydrogen bonding, as well as coulombic forces, act as a... 

Use of sulfonated polymers as the proton-conductive component in the fuel cell membranes at T < 100°C Use of nonfluorinated ionomers physical and/or chemical cross-linking of the fuel cell membranes Use of nonfluorinated ionomers physical and/or chemical cross-linking of the fuel cell membranes Development of organic-inorganic composite membranes, based on our cross-linked ionomer membrane systems, in which the inorganic membrane component serves as water storage or even contributes to H -conduction Use of commercially available polymers for chemical modification and membrane formation, which avoids expensive development of novel polymers... 

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