ASAXS study of styrene-grafted sulfonated poly(vinylidene fluoride) membranes

Torkkeli, Mika; Serimaa, Ritva; Eteläniemi, V.; Toivola, Minna; Jokela, K.; Paronen, Mikael; Sundholm, Franciska

doi:10.1002/1099-0488(20000701)38:13<1734::aid-polb70>3.0.co;2-z

Cited by 16 publications

(14 citation statements)

References 20 publications

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“…It is well known that PVDF is a semicrystalline polymer forming lamellar stacks [32±35] and previous experiments have shown that the structure is still lamellar after grafting and sulfonation [31]. The SAXS intensities of all the current samples show a pronounced peak arising from the lamellar structures [32,33].…”

Section: Resultsmentioning

confidence: 70%

Relationship Between Methanol Permeability and Structure of Different Radiation‐Grafted Membranes

Kallio¹,

Kisko²,

Kontturi³

et al. 2004

Fuel Cells

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Styrene grafted and sulfonated poly(vinylidene fluoride) and poly(vinylidene fluoride‐co‐hexafluoropropylene) films are candidates as electrolytes in direct methanol fuel cells. Their behaviour in water, 1 and 3 mol dm–3 aqueous methanol, and pure methanol were studied. According to SAXS results, water and methanol‐water solutions have similar effects on the membranes, i.e., the lamellar period increases and the ionic domains enlarge. Furthermore, differences in the ionic domain structures in pure methanol and water were observed. These structural changes together with dissimilar liquid uptakes in water and in methanol are reflected as changes in the conductivities. An increase in the SAXS intensity and changes in the Bragg distance of the ionic peak were observed in methanol compared to aqueous solutions. This may be related to the hydrophobicity of the CH3 group on methanol. Dissimilarities in methanol permeability through the radiation‐grafted membrane can be related to structural differences in membranes observed with SAXS. Permeabilities were observed to be lower for the radiation‐grafted membranes compared to Nafion® 115, which compensates for the higher area resistance of the experimental membranes and thus improves their performance in a fuel cell.

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Section: Resultsmentioning

confidence: 70%

Relationship Between Methanol Permeability and Structure of Different Radiation‐Grafted Membranes

Kallio¹,

Kisko²,

Kontturi³

et al. 2004

Fuel Cells

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“…This radiation technique allows us to introduce various functional grafted polymers directly bonded to the main chains of polymer substrates, while the inherent characteristics of the polymer substrates such as thermal stability, mechanical strength, and crystallinity are still retained. Morphology of the graft‐type PEMs prepared by the above radiation grafting technique has been intensively investigated using the small‐angle scattering methods with various matrix polymers of poly(tetrafluoroethylene) (PTFE), poly(ether ether ketone) (PEEK), poly(vinylidene fluoride) (PVDF), and poly(ethylene‐ co ‐tetrafluoroethylene) (ETFE) . Consequently, various general features have been well‐established as follows.…”

Section: Introductionmentioning

confidence: 99%

“…The sulfonic acid–water clusters were observed to form in the amorphous polymer matrix of PEEK, PVDF, and ETFE. The matrix polymers (PTFE, PEEK, PVDF, ETFE) possessed the layered structures (lamellae) and the variation of these structures depended on the amount of grafted materials . In addition, the crystalline structures and the hydrophilic phases generated by the introduction of the graft materials were found to play an important role in the mechanical integrity and conductivity of the membranes, respectively.…”

Section: Introductionmentioning

confidence: 99%

SAXS Investigation on Morphological Change in Lamellar Structures During Propagation Steps of Graft‐Type Polymer Electrolyte Membranes for Fuel Cell Applications

Tap

Nguyen

Zhao³

et al. 2019

Macro Chemistry & Physics

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their advantages over other fuel cells in terms of the clean and efficient power generation and lower operating temperature. [1] They are expected to reduce the fossil fuel consumption, which is believed to be the primary sources causing the climate change. PEM, which consists of super acid groups (i.e., sulfonic acid), has been considered as one of the key components in achieving the high fuel cell performance because of its unique fuel cell properties such as ionic conductance, mechanical strength, and thermal and chemical stabilities. When a dry PEM is immersed in water, the hydrophilic chains with sulfonic ion groups can absorb water and consequently form the interconnected ion channels inside the hydrated regions. The macro and microphase separations, viz., crystalline morphologies, conducting layers (ion channels), characteristic domain sizes, and the connection and distribution of the ionic groups and water in the conducting layers and around the crystalline phases are believed to play an important role in the conductivity and mechanical integrity of the PEMs. [2][3][4] Currently, the main challenges to improve the conductivity and mechanical strength of the PEMs are the lack of detailed informationThe changes of the lamellar periods (L 1D ), thickness of lamellar crystals (L c ), and amorphous layers (L a ) within the stacked lamellae of poly(styrenesulfonic acid)-grafted poly(ethylene-co-tetrafluoroethylene) polymer electrolyte membranes (ETFE-PEMs), induced by the preparation and water-absorbing steps are investigated using the small-angle X-ray scattering method. The L 1D values of all the samples quickly increase at a grafting degree (GD) range of less than 19% and then level off. The solvent-induced recrystallization is observed at the early stage of grafting (GD < 10%) and at successive sulfonation and hydration steps. The L 1D , L a , and L c of dry and hydrated PEMs show similar values at higher GD ranges (>34%), leading to the conclusion that most water molecules in the PEMs with higher GDs exist at the outside of the lamellar stacks. Accordingly, for the PEMs with low GD (<19%), all the hydrophilic graft-polymers (ion-channels) locate in the lamellar stacks and are strongly restricted by lamellar crystalline layers, which suppress the swelling of the PEMs. The unique lamellar structures of ETFE-PEMs characterized by L a and L c are well connected with the high conductance and mechanical properties of the membranes, and are suitable for fuel cell applications.

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“…[2][3][4] The structure and properties of styrene-grafted and sulfonated poly(vinylidene fluoride) (PVDFg-PSSA) have been studied so that new membrane materials can be obtained for fuel cell applications. [5][6][7][8][9][10][11] In these earlier studies, poly(vinylidene fluoride) (PVDF) was used as a matrix polymer irradiated with electrons and then grafted with styrene into the matrix. The final proton-conducting membrane was obtained when the grafted styrene was sulfonated.…”

Section: Introductionmentioning

confidence: 99%

Effect of the initial matrix material on the structure of radiation‐grafted ion‐exchange membranes: Wide‐angle and small‐angle X‐ray scattering studies

Jokela

Serimaa

Torkkeli

et al. 2002

J Polym Sci B Polym Phys

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Seven different fluoropolymer films were used as matrix materials for radiation-grafted ion-exchange membranes. The crystallinity and preferred orientation of these membranes were studied with wide-angle X-ray scattering, and the lamellar structure of the membranes was examined with small-angle X-ray scattering. The crystallinity of poly(vinylidene fluoride) (PVDF)-based matrix materials varied between 57 and 40%, and the crystallinity of the sulfonated samples varied between 34 and 23%. The lamellar periods of PVDF-based matrix materials were about 115 Å, and the lamellar periods of poly(ethylene-alt-tetrafluoroethylene) and poly(tetrafluoroethyleneco-hexafluoropropylene) were 250 and 212 Å, respectively. When the samples were grafted, the lamellar periods increased. Correlation function analysis showed very clearly that the long-range order decreased because of grafting and sulfonation processes. For those samples that showed good proton conductivity, the lamellar period also increased because of sulfonation.

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ASAXS study of styrene-grafted sulfonated poly(vinylidene fluoride) membranes

Cited by 16 publications

References 20 publications

Relationship Between Methanol Permeability and Structure of Different Radiation‐Grafted Membranes

Relationship Between Methanol Permeability and Structure of Different Radiation‐Grafted Membranes

SAXS Investigation on Morphological Change in Lamellar Structures During Propagation Steps of Graft‐Type Polymer Electrolyte Membranes for Fuel Cell Applications

Effect of the initial matrix material on the structure of radiation‐grafted ion‐exchange membranes: Wide‐angle and small‐angle X‐ray scattering studies

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