| 1. |
- Takamuku, Shogo, et al.
(författare)
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Segmented tetrasulfonated copoly(arylene ether sulfone)s: improving proton transport properties by extending the ionic sequence
- 2013
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Ingår i: ChemSusChem. - : Wiley. - 1864-564X .- 1864-5631. ; 6:2, s. 308-319
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Tidskriftsartikel (refereegranskat)abstract
- The morphologies and proton-transport efficiencies of segmented copoly(arylene ether sulfone) ionomers that contain tetrasulfonated sequences are compared with the corresponding copolymers with disulfonated sequences. Tetrasulfonated 4,4′-bis[(4-chlorophenyl)sulfonyl]-1,1′-biphenyl (sBCPSBP) is synthesized by metalation and sulfination. This new monomer is then used in K2CO3-mediated polycondensations of mixtures with 4,4′-dichlorodiphenyl sulfone (DCDPS) and 4,4′-dihydroxybiphenyl in dimethyl sulfoxide at 110 °C to prepare segmented copolymers with tetrasulfonated units. The corresponding disulfonated copolymers are prepared by using disulfonated DCDPS instead of sBCPSBP. Small-angle X-ray scattering measurements of the fully aromatic copolymer membranes show ionomer peaks that indicate significantly larger characteristic separation lengths of the tetrasulfonated copolymers compared to those of the corresponding disulfonated copolymers with similar ionic contents. This implies a much more efficient phase separation of the ionic groups in the segmented tetrasulfonated copolymer membranes, especially at low-to-medium ionic contents. The enhanced phase separation has a pronounced positive effect on water uptake characteristics and proton transport properties. Under a reduced relative humidity (RH), the tetrasulfonated copolymer membranes show a significantly higher conductivity than the disulfonated ones, particularly at low-to-medium ionic contents. At an ion-exchange capacity of 1 meq g−1, the conductivity of the tetrasulfonated copolymer membrane at 30 % RH is higher than that of the disulfonated membrane at 90 % RH. Because of their relative ease of synthesis, segmented copolymers based on well-designed multisulfonated monomers may provide a viable alternative to the more complex sulfonated block and graft copolymers for use as fuel-cell membranes.
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| 2. |
- Weiber, Annika, et al.
(författare)
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Ion distribution in quaternary ammonium functionalized aromatic polymers: effects on the ionic clustering and conductivity of anion exchange membranes
- 2014
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Ingår i: ChemSusChem. - : Wiley. - 1864-564X .- 1864-5631. ; 7:9, s. 2621-2630
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Tidskriftsartikel (refereegranskat)abstract
- A series of copoly(arylene ether sulfone)s having precisely two, three or four quaternary ammonium (QA) groups clustered directly on single phenylene rings along the backbone are studied as anion exchange membranes. The copolymers are synthesized via condensation polymerizations involving either di-, tri- or tetramethylhydroquinone, followed by virtually complete benzylic bromination using N-bromosuccinimide and quaternization with trimethylamine. This synthetic strategy allows an excellent control and systematic variation of the local density and distribution of QA groups along the backbone. Small angle X-ray scattering of these copolymers shows extensive ionic clustering, promoted by an increasing density of QA on the single phenylene rings. At an ionexchangecapacity (IEC) of 2.1 meq. g-1, the water uptake decrease with an increasing local density of QA groups. Moreover, at moderate IECs at 20 °C the Br- conductivity of the densely functionalized copolymers is higher than a corresponding randomly functionalized polymer, despite the significantly higher water uptake of the latter. Thus, placing multiple cations on single aromatic rings in the polymers facilitates the formation of a distinct percolating hydrophilic phase domain with high ionic concentration to promote efficient anion transport, despite probable limitations by reduced ion dissociation. These findings imply a viable strategy to improve the performance of alkaline membrane fuel cells.
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| 3. |
- Sedrik, Rauno, et al.
(författare)
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Aromatic Polymethacrylates from Lignin-Based Feedstock: Synthesis, Thermal Properties, Life-Cycle Assessment and Toxicity
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Ingår i: ChemSusChem. - 1864-564X.
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Tidskriftsartikel (refereegranskat)abstract
- There is currently a great need for rigid, high-performance and processable bio-based polymers and plastics as alternatives to the fossil-based materials used today. Here, we report on the straightforward synthesis and polymerization of lignin-derived methacrylate monomers based on the methyl esters of syringic, vanillic, and 4-hydroxybenzoic acid, respectively. The corresponding homopolymethacrylates exhibit high glass transition temperatures (Tgs) at 106, 128, and 197 °C, respectively. Rheological properties and thermal stability up to at least 277 °C indicate that these polymers are melt-processable. In addition, copolymers with methyl methacrylate are prepared to further vary and tune the polymer properties. An integrated ex-ante and prospective life-cycle assessment of key environmental impact parameters indicates similar or only slightly higher values compared to well-established fossil-based methyl methacrylate. Moreover, the toxicity towards human HeLa cell lines compares well with that of poly(methyl methacrylate). Hence, the potential availability of lignin-derived acids, combined with the straightforward and potentially upscalable monomer synthesis, make these rigid polymers appealing alternatives towards bio-based high-Tg thermoplastic materials with low toxicity.
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| 4. |
- Xia, Yifan, et al.
(författare)
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Poly(arylene alkylene)s with Tetrazole Pendants for Alkaline Ion-Solvating Polymer Electrolyte
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Ingår i: ChemSusChem. - 1864-564X.
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Tidskriftsartikel (refereegranskat)abstract
- Alkaline ion-solvating membranes derived from a tetrazole functionalized poly(arylene alkylene) are prepared, characterized and evaluated as electrode separators in alkaline water electrolysis. The base polymer, poly[[1,1′-biphenyl]-4,4′-diyl(1,1,1-trifluoropropan-2-yl)], is synthesized by superacid catalyzed polyhydroxyalkylation and subsequently functionalized with tetrazole pendants. After equilibration in aqueous KOH, the relatively acidic tetrazole pendants are deprotonated to form the corresponding potassium tetrazolides. The room temperature ion conductivity is found to peak at 19 mS cm−1 in 5 wt. % KOH, and slightly declines with increasing KOH concentration to 13 mS cm−1 in 30 wt. % KOH. Based on an overall assessment of the mechanical properties, conductivity and electrode activity, 30 wt. % KOH is applied for alkaline electrolysis cell tests. Current densities of up to 1000 mA cm−2 were reached with uncatalyzed Ni-foam electrodes at a cell voltage of less than 2.6 V, with improved gas barrier characteristics compared to that of the several times thicker Zirfon separator.
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