Local and long-range structure of water in a perfluorinated ionomer membrane

Lee, E. M.; Thomas, Riya; Burgess, A. N.; Barnes, David; Soper, A. K.; Rennie, A. R.

doi:10.1021/ma00038a013

Cited by 35 publications

(25 citation statements)

References 2 publications

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“…However, the structure could alternatively be envisioned as having isolated ordered regions with a highly ordered layered crystalline-type structure (such as those suggested by Starkweather [11], Litt [15], Ozerin et al [5,6], or Rebrov et al [16]), dispersed within a matrix of less well-ordered material. A general structural interpretation of this sort is easily reconciled with reported crystallinity values from x-ray diffraction in the 10-15% range [2,11] and consistent with reports of a networked channel structure in the membranes [21]. For a dispersed layered crystalline-phase model, the disparity in the ionic feature spacing and crystalline feature spacing slopes would be indicative of the preference of the particular solvent for the matrix relative to the layeredcrystalline regions rather than evidence against a layered structure.…”

Section: Resultssupporting

confidence: 80%

Investigation of the Morphological Changes in Nafion Membranes Induced by Swelling with Various Solvents

Young¹,

Trevio²,

Tan³

2002

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The structure of Nafiort 117 perfluorosulfonate ionomer membranes has been investigated using small-angle neutron-scattering techniques. Structural changes induced by swelling of the membranes with water, alcohols, and dipolar aprotic solvents were monitored, at solvent swelling levels ranging from -2% to >50%, by volume. Membranes swollen up to -50 volume-percent solvent exhibited two scattering maxima: one known to be associated with ionic regions of the membrane structure and one known to be associated with correlation distances between crystalline regions in the membrane structure. The positions of both maxima shifted toward lower q values as the solvent content in the membrane increased. The shift in the position of both maxima was linearly related to the volume fraction of solvent in the membrane. The Bragg spacings corresponding to both the ionic feature scattering maximum and the crystalline feature scattering maximum were plotted vs. volume fraction of solvent in the membranes and the data fit using linear regression. The slopes associated with the spacing vs. volume fraction solvent curves were greater for the crystalline feature spacing than for the ionic feature spacing for all solvents other than water, indicative of preferential segregation of non-aqueous solvents into regions of the structure not directly associated with the ionic scattering maximum.u

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Section: Resultssupporting

confidence: 80%

Investigation of the Morphological Changes in Nafion Membranes Induced by Swelling with Various Solvents

Young¹,

Trevio²,

Tan³

2002

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“…The validity of such a structure has been supported by both theoretical (Eisenberg, 1970;Hsu and Gierke, 1982) and experimental (Gierke et al, 1981;Xue et al, 1989;Lee et al, 1992) observations. Readers are referred to review articles by Mauritz (1988) and Heitner-Wirguin (1996) for more information.…”

Section: Introductionmentioning

confidence: 81%

Micromechanical analysis of ionic clustering in Nafion perfluorinated membrane

Nemat‐Nasser

2000

Mechanics of Materials

105

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The cluster morphology in a water-swollen Na®on per¯uorinated membrane is studied using a micromechanics approach. The cluster size is determined from the minimization of the free energy as a function of the equivalent weight of Na®on, the volume fraction of water, and the temperature, taking into account the electrostatic dipole interaction energy, the elastic polymer chain reorganization energy, and the cluster surface energy, leading to results which are in accord with experimental observations. By minimizing the sum of: (1) the electro-elastic interaction energy between an ionic cluster and the¯uorocarbon matrix, and (2) the cluster surface energy, it is concluded that the eective cluster shape is spherical in the absence of an electric ®eld, and becoming an oblate spheroid when an electric ®eld is applied. The eect of cluster morphology on the eective electro-elastic moduli and the eective ionic conductivity is then studied by a micromechanical multi-inclusion model. The result seems to describe the available empirical relation when a spherical cluster shape is assumed. It correctly predicts the insulator-to-conductor transition which occurs in Na®on, as the water volume fraction is increased. Ó

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“…With the increment of heat treatment temperature, more energy was provided to produce a higher crystallinity. The cluster network model of PFSA proposed by Gierke32, 33 gave a reasonable account for PV process of PFSA membrane. During the annealing process (heat treatment), the main chains containing CF 2  gradually crystallize, the SO 3 − and counterions form ion‐clusters.…”

Section: Resultsmentioning

confidence: 99%

Preparation of PFSA‐PVA/PSf hollow fiber membrane for IPA/H₂O pervaporation process

Lang

Tong

2007

J of Applied Polymer Sci

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Using Na 1 form of perfluorosulfonic acid (PFSA) and poly(vinyl alcohol) (PVA) as coating materials, polysulfone (PSf) hollow fiber ultrafiltration membrane as a substrate membrane, PFSA-PVA/PSf hollow fiber composite membrane was fabricated by dip-coating method. The membranes were post-treated by two methods of heat treatment and by both heat treatment and chemical crosslinking. Maleic anhydride (MAC) aqueous solution was used as chemical crosslinking agent using 0.5 wt % H 2 SO 4 as a catalyst. PFSA-PVA/PSf hollow fiber composite membranes were used for the pervaporation (PV) separation of isopropanol (IPA)/H 2 O mixture. Based on the experimental results, PFSA-PVA/PSf hollow fiber composite membrane is suitable for the PV dehydration of IPA/H 2 O solution. With the increment of heat treatment temperature, the separation factor increased and the total permeation flux decreased. The addition of PVA in PFSA-PVA coating solution was favorable for the improvement of the separation factor of the composite membranes post-treated by heat treatment. Compared with the membranes by heat treatment, the separation factors of the composite membranes post-treated by both heat treatment and chemical crosslinking were evidently improved and reached to be about 520 for 95/5 IPA/water. The membranes posttreated by heat had some cracks which disappeared after chemical crosslinking for a proper time. Effects of feed temperature on PV performance had some differences for the membranes with different composition of coating layer. The composite membranes with the higher mass fraction of PVA in PFSA-PVA coating solution were more sensitive to temperature. It was concluded that the proper preparation conditions for the composite membranes were as follows: firstly, heated at 1608C for 1 h, then chemical crosslinking at 408C for 3 h in 4% MAC aqueous solution.

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Local and long-range structure of water in a perfluorinated ionomer membrane

Cited by 35 publications

References 2 publications

Investigation of the Morphological Changes in Nafion Membranes Induced by Swelling with Various Solvents

Investigation of the Morphological Changes in Nafion Membranes Induced by Swelling with Various Solvents

Micromechanical analysis of ionic clustering in Nafion perfluorinated membrane

Preparation of PFSA‐PVA/PSf hollow fiber membrane for IPA/H₂O pervaporation process

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Local and long-range structure of water in a perfluorinated ionomer membrane

Cited by 35 publications

References 2 publications

Investigation of the Morphological Changes in Nafion Membranes Induced by Swelling with Various Solvents

Investigation of the Morphological Changes in Nafion Membranes Induced by Swelling with Various Solvents

Micromechanical analysis of ionic clustering in Nafion perfluorinated membrane

Preparation of PFSA‐PVA/PSf hollow fiber membrane for IPA/H2O pervaporation process

Contact Info

Product

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Preparation of PFSA‐PVA/PSf hollow fiber membrane for IPA/H₂O pervaporation process