Highly Stable, Low Gas Crossover, Proton‐Conducting Phenylated Polyphenylenes

Adamski, Michael; Skalski, Thomas J. G.; Britton, Benjamin; Peckham, Timothy J.; Metzler, Lukas; Holdcroft, Steven

doi:10.1002/anie.201703916

Cited by 94 publications

(163 citation statements)

References 41 publications

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“…The findings presented herein are consistent with previously published mechanical properties of post-sulfonated phenylated polyphenylenes, [14] as well as presulfonated derivatives. [19] Theoretical (IEC th )a nd experimental (IEC xp )i on exchange capacity values, calculated and determined by titration experiments,r espectively,a re shown in Figure2.T hey follow al inear trend from sPPP(0.5)-H + + (IEC th = 2.17 meq g À1 )t ot he homopolymer sPPP(1.0)-H + + (IEC th = 3.70 meq g À1 ). The experimental IECs closely matched their theoretical counterparts, as previously observed.…”

Section: Resultsmentioning

confidence: 94%

“…[19] Theoretical (IEC th )a nd experimental (IEC xp )i on exchange capacity values, calculated and determined by titration experiments,r espectively,a re shown in Figure2.T hey follow al inear trend from sPPP(0.5)-H + + (IEC th = 2.17 meq g À1 )t ot he homopolymer sPPP(1.0)-H + + (IEC th = 3.70 meq g À1 ). [13,19] These data provide insightt op olymer tunability according to the ratios of hydrophilic and hydrophobic monomers used. [13,19] These data provide insightt op olymer tunability according to the ratios of hydrophilic and hydrophobic monomers used.…”

Section: Resultsmentioning

confidence: 94%

“…Previously published [19] methodologies were used to determine the polymer water sorption characteristics, including water uptake, water content, dimensional stability (volumetric expansion or volume uptake), ion exchange capacity (IEC), number of water molecules per sulfonic group (l,m ol H 2 Op er mol of ÀSO 3 H), membrane analytical acid concentration [SO 3 H],a nd effective proton mobility (m eff ). Ad etailed outline can be found in the Supporting Information.…”

Section: Dimensional Stabilityion Exchange Capacityand Water Sorptimentioning

confidence: 99%

“…[9] Althoughe ffective, post-functionalization strategies are synonymous with al ack of reproducibility,w ith limited control over the location of the hydrophilic functionalg roup on the resulting functionalized polymer, and non-integer degrees of functionalization. [9,13,[19][20][21] The presence of both hydrophilic and hydrophobic moieties on ion-conducting polymers drives phase segregation into respectived omains, [6,[22][23][24] which facilitates the formation of ionic clusters and channels throughout the materials prepared therefrom.T hese nano-and microscopic morphological features are critical to their properties as ion-conducting media. [9,13,[19][20][21] The presence of both hydrophilic and hydrophobic moieties on ion-conducting polymers drives phase segregation into respectived omains, [6,[22][23][24] which facilitates the formation of ionic clusters and channels throughout the materials prepared therefrom.T hese nano-and microscopic morphological features are critical to their properties as ion-conducting media.…”

Section: Introductionmentioning

confidence: 99%

“…[16,[49][50][51] Owing to the high stabilityo f the backbone, simple synthesis, and promising initial PEM properties, sPPP becameatopic of interest. [13,19] Additionally, by modifying the dienophile monomer,w ep repared homopolymers with different hydrophobic segments to control the IEC, lower their water uptake and swelling, andtotune proton conductivity. [14,41,52] Second, despite reporting as ynthetic approach that allowed for tuning the polymerI EC, the random and irreproducible natureo fp ostsulfonation gave irregular functionalizations on the polymer backbone, in the range of 0.8-2.1 sulfonica cid groups per repeatu nit.…”

Section: Introductionmentioning

confidence: 99%

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Sulfophenylated Terphenylene Copolymer Membranes and Ionomers

et al. 2018

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The copolymerization of a prefunctionalized, tetrasulfonated oligophenylene monomer was investigated. The corresponding physical and electrochemical properties of the polymers were tuned by varying the ratio of hydrophobic to hydrophilic units within the polymers. Membranes prepared from these polymers possessed ion exchange capacities ranging from 1.86 to 3.50 meq g−1 and exhibited proton conductivities of up to 338 mS cm−1 (80 °C, 95 % relative humidity). Small‐angle X‐ray scattering and small‐angle neutron scattering were used to elucidate the effect of the monomer ratios on the polymer morphology. The utility of these materials as low gas crossover, highly conductive membranes was demonstrated in fuel cell devices. Gas crossover currents through the membranes of as low as 4 % (0.16±0.03 mA cm−2) for a perfluorosulfonic acid reference membrane were demonstrated. As ionomers in the catalyst layer, the copolymers yielded highly active porous electrodes and overcame kinetic losses typically observed for hydrocarbon‐based catalyst layers. Fully hydrocarbon, nonfluorous, solid polymer electrolyte fuel cells are demonstrated with peak power densities of 770 mW cm−2 with oxygen and 456 mW cm−2 with air.

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 94%

Section: Dimensional Stabilityion Exchange Capacityand Water Sorptimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sulfophenylated Terphenylene Copolymer Membranes and Ionomers

et al. 2018

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Weakly Humidity‐Dependent Proton‐Conducting COF Membranes

et al. 2020

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phase-separated copolymer membranes, often suffer from dramatically declined proton conductivity at low relative humidity (RH), [6-10] because the severe water loss under low RH destructs watermediated hydrogen-bonding networks. [8,11] For decades, great effort has been devoted to reduce the humidity-dependence of conductivity through preserving membrane hydration under low RH, such as incorporating hydrophilic groups [12,13] or hygroscopic porous nanofillers into membranes [7,14] to improve water retention properties, and installing nanovalves to retard water desorption of membranes. [2] However, the water retention remains a daunting challenge due to the "flexible polymer networks" nature of these PEMs. The amorphous, flexible ion nanochannels are prone to shrinking and even breaking upon dehydration, leading to poorly connected water channels and consequently exponential decline in conductivity and fuel cell performance. [6,15] Therefore, the design of electrolyte materials with weakly humidity-dependent proton-conducting feature remains a challenge. Materials with crystalline and rigid nanochannels are able to firmly retain water by capillary forces [16-20] and may promote membrane hydration, thereby facilitating proton transport efficiently over a wide range of humidity. Covalent organic frameworks (COFs), a class of crystalline porous polymers with pre-designable pore structures, hold grand promise. [21-23] Unlike amorphous, flexible crosslinked networks, the crystalline, rigid organic frameworks of COFs are expected to afford well-defined and stable proton-conducting nanochannels, [24-30] as well as good water retention capability. [18] However, leveraging COF materials in the field of COF-based PEMs for practical application remains a great challenge arising from the poor processing ability of COF materials and the poor structural integrity of COF membranes. Moreover, the proton transport mechanism in crystalline and rigid nanochannels of COF membranes remains elusive. Herein, we report a diffusion and solvent co-mediated modulation strategy for the direct synthesis of highly crystalline IPC-COF nanosheets (NUS-9) that can be readily processed into defect-free, robust IPC-COF membranes by subsequent vacuum-assisted self-assembly. These IPC-COF membranes exhibit weakly humidity-dependent conductivity and fuel cell performance over a wide range of humidity (30-98%). We further demonstrate that the crystalline and rigid ion nanochannels render the IPC-COF membranes exceptional State-of-the-art proton exchange membranes (PEMs) often suffer from significantly reduced conductivity under low relative humidity, hampering their efficient application in fuel cells. Covalent organic frameworks (COFs) with pre-designable and well-defined structures hold promise to cope with the above challenge. However, fabricating defect-free, robust COF membranes proves an extremely difficult task due to the poor processability of COF materials. Herein, a bottom-up approach is developed to synthesize intrinsic proton-conducting COF...

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