Counterion ionomer, effect

Kadirov MK, Bosnjakovic A, Schlick S (2005) Membrane-derived fluorinated radicals detected by electron spin resonance in UV-irradiated Nation and Dow ionomers effect of counterions and H202. J Phys Chem B 109(16) 7664-70... 

Jing, F., Hou, M., Shi, W, Fu, J., Yu, H., Ming, P. and Yi, B. (2007) The effect of ambient contamination on PEMFC performance. J. Power Sources 166, 172-176 Kadirov, M. K., Bosnjakovic, A. and Schlick, S. (2005) Membrane-derived fluorinated radiceds detected by electron spin resonance in UV-irradiated Nafion and Dow ionomers Effect of counterions and H O - J- Phys. Chem. B 109, 7664-7670 Kelly, M. J., Egger, B., Fafilek, G., Besenhard, J. O., Kronberger, H. and Nauer, G. E. (2005a) Conductivity of polymer electrolyte membranes by impedance spectroscopy with microelectrodes. Solid State Ionics 176, 2111-2114... 

For partially crystalline ionomers, such as those based on copolymers of ethylene and methacrylic acid, even time or aging at room temperature can have an effect on mechanical properties. For example, upon aging at 23°C, the modulus of the acid form of the copolymer increased 28%, while in the ionomer form, the increase ranged up to 130%, with the specific gain in modulus depending on the degree of conversion and on the counterion that was present [17]. 

The type of counterion present in an ionomer may, or may not, have a significant effect of properties. For polyethylene-based ionomers, where the presence of crystallinity has an appreciable effect on properties, the type of counterion present does not appear to have a significant effect on either modulus or tensile strength, as Fig. 4 indicates. However, in amorphous ionomers, the effects of changing the counterion from a monovalent one, as in Na or K, to a divalent one, such as Ca, may be appreciable. 

The combined effects of a divalent Ca counterion and thermal treatment can be seen from studies of PMMA-based ionomers [16]. In thin films of Ca-salts of this ionomer cast from methylene chloride, and having an ion content of only 0.8 mol%, the only observed deformation was a series of long, localized crazes, similar to those seen in the PMMA homopolymer. When the ionomer samples were subject to an additional heat treatment (8 h at 100°C), the induced crazes were shorter in length and shear deformation zones were present. This behavior implies that the heat treatment enhanced the formation of ionic aggregates and increased the entanglement strand density. The deformation pattern attained is rather similar to that of Na salts having an ion content of about 6 mol% hence, substitution of divalent Ca for monovalent Na permits comparable deformation modes, including some shear, to be obtained at much lower ion contents. 

Aside from ion content, a wide range of properties is available in ionomers by control of various processing variables, such as degree of conversion (neutralization), type of counterion, plasticizer content and thermal treatment. Various examples illustrating possible effects of these variables on mechanical relaxation behavior and on such mechanical properties as stiffness, strength, and time- or energy-to-fracture have been given. 

Landis, F A. and Moore, R. B. 2000. Blends of a perfluorosulfonate ionomer with poly(vinylidene fluoride) Effect of counterion type on phase separation and crystal morphology. Macromolecules 33 6031-6041. 

K.M. Cable, K.A. Mauritz, and R.B. Moore. Effects of hydrophihc and hydrophobic counterions on the coulombic interactions in perfluorosulfonate ionomers. Journal of Polymer Science Part B-Polymer Physics 33, 1065-1072 1995. 

Effective diameters of lonomers can be used to discuss quantitatively the effects of various molecular parameters, such as ion content and counterions, on the structure of ionomers. For example, for the ion content effeet it is found (18) that D Increases linearly from 420 A for PS, which is close to the°root-mean-square end-to-end distance of PS, to ca. 3100 A at 6 mol % ion content. The linear relationship between D and ion content, f, is expressed as... 

Also, for the counterion effect on the effective diameters it is found (18) that Do decreases with Increasing ionic radius of the counterions 1800 A for Na Jon (0.96 X), 1600 X for K ion (1.33 A), and 1500 A for Cs ion (1.69 A). Original Kc/Rq vs. c curves were reported elsewhere (16). We also pointed out by viscosity measurements (li) that for sulfonated ionomers, the effect of counterion (i.e., counterion binding) Increased in the order of Li < Na < K < Cs, since the solvated ion size decreased in the order of Li > Na > K > Cs. Light scattering results show this tendency more quant i tat ively. 

With regard to counterion binding, some similarities are also observed between ionomer nonaqueous solution and polyelectrolyte aqueous solution. This is the short-range effect due to partial desolvation associated with coun-... 

Agarwal PK, Garner RT, Graessley WW. Counterion and solvent effects on the dilute solution viscosity of polystyrene ionomers. J Polym Sci Polym Phys Ed 1987 25 2095-2111. 

Effect of Counterion Structure on Ionomer Properties Quaternary Phosphonium Counterions in Sulfonated EPDM... 

T he type of counterion used in an ion-containing polymer can have a substantial effect on the physical properties of the material. Many studies have been made in the past comparing the properties of metal- or ammonium-neutralized ionomers two recent books on ion-containing polymers present a comprehensive review of the literature (1,2). There is a wealth of information comparing different metal counterions in neutralized or partially neutralized ethylene-carboxylic acid copolymers. Rees and Vaughan studied the melt flow and tensile properties of... 

Several groups have found that counterions have a great effect on the thermal stability of perfluoro-sulfonated ionomer membranes (Feldheim et al, 1993 Lage et al., 2004a,b Bas et al., 2009). Using TG analysis, Feldheim et al. (1993) found the thermal stability of Nafion perfluorosulfonated ionomer to be... 

Cable, K. M., Mauritz, K. A., and Moore, R. B. 1995. Effects of hydrophilic and hydrophobic counterions on the Coulombic interactions in perfluorosulfonate ionomers. 

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