Ion transport properties of mechanically stable symmetric ABCBA pentablock copolymers with quaternary ammonium functionalized midblock

Ertem, S. Piril; Caire, Benjamin R.; Tsai, Tsung Han; Zeng, Di; Vandiver, Melissa A.; Kusoglu, Ahmet; Seifert, Söenke; Hayward, Ryan C.; Weber, Adam Z.; Herring, Andrew M.; Coughlin, E. Bryan; Liberatore, Matthew W.

doi:10.1002/polb.24310

Cited by 22 publications

(15 citation statements)

References 61 publications

(105 reference statements)

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“…Solid lines are Park model fitting.Mechanical properties. The stress-strain characteristics of HMT-PMBI, PPO-TMA and PPO-AGO changed between drier and wetter conditions at 60 o C, which agrees with other AEMs and PEMs 76,[85][86][87][88][89]. By using two different humidities, the range of mechanical properties of a film can be captured within the context of the water uptake study; a more exhaustive study81 was not completed as it is outside of the scope of this work.…”

supporting

confidence: 69%

Water Uptake Study of Anion Exchange Membranes

et al. 2018

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Anion exchange membrane fuel cells (AEMFCs) have attracted extensive attention in the recent years, primarily due to the distinct advantage potentials they have over the mainstream proton exchange membrane fuel cells. The anion exchange membrane (AEM) is the key component of AEMFC systems. Due to the unique characteristics of water management in AEMFCs, understanding the water mobility through AEMs is key for this technology, as it significantly affects (and limits) overall cell performances. This work presents a study of the equilibrium state and kinetics of water uptake (WU) for AEMs exposed to vapor source H2O. We investigate different AEMs that exhibit diverse water uptake behaviors. AEMs containing different backbones (fluorinated and hydrocarbon-based backbones) and different functional groups (various cations as part of the backbone or as pendant groups) were studied. Equilibrium WU isotherms are measured and fitted by the Park model. The influence of relative humidity and temperature is also studied for both equilibrium and dynamic WU. A characteristic time constant is used to describe WU kinetics during the H2O sorption process. To the best of our knowledge, this is the first time that WU kinetics has been thoroughly investigated on AEMs containing different backbones and cationic functional groups. The method and analysis described in this work provides critical insights to assist with the design of the next generation anion conducting polymer electrolytes and membranes for use in advanced, high-performance AEMFCs.

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confidence: 69%

Water Uptake Study of Anion Exchange Membranes

et al. 2018

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“…However, AAEM conductivity is significantly influenced by hydrophobic-hydrophilic microphase separation, because a well-defined polymer morphology (e.g., bicontinuous hydrophobic-hydrophilic channels) facilitates water/hydroxide transportation in solid-state membranes (14). In previous reports, modifying polymer morphology with multiblock sequences (15)(16)(17)(18), long flexible side chains (18)(19)(20)(21), or microporous structures (22) has improved hydroxide conductivity. For instance, Watanabe and coworkers (15) observed that multiblock poly(arylene ether)s showed significantly higher hydroxide conductivity than their random copolymer analogs [σ (OH − , 60°C) = 126 mS/cm and 35 mS/cm for multiblock and random copolymers, respectively.…”

mentioning

confidence: 99%

Highly conductive and chemically stable alkaline anion exchange membranes via ROMP of trans -cyclooctene derivatives

You

Padgett

MacMillan

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

134

107

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Alkaline anion exchange membranes (AAEMs) are an important component of alkaline exchange membrane fuel cells (AEMFCs), which facilitate the efficient conversion of fuels to electricity using nonplatinum electrode catalysts. However, low hydroxide conductivity and poor long-term alkaline stability of AAEMs are the major limitations for the widespread application of AEMFCs. In this paper, we report the synthesis of highly conductive and chemically stable AAEMs from the living polymerization of trans-cyclooctenes. A trans-cyclooctene-fused imidazolium monomer was designed and synthesized on gram scale. Using these highly ring-strained monomers, we produced a range of block and random copolymers. Surprisingly, AAEMs made from the random copolymer exhibited much higher conductivities than their block copolymer analogs. Investigation by transmission electron microscopy showed that the block copolymers had a disordered microphase segregation which likely impeded ion conduction. A cross-linked random copolymer demonstrated a high level of hydroxide conductivity (134 mS/cm at 80°C). More importantly, the membranes exhibited excellent chemical stability due to the incorporation of highly alkaline-stable multisubstituted imidazolium cations. No chemical degradation was detected by 1 H NMR spectroscopy when the polymers were treated with 2 M KOH in CD 3 OH at 80°C for 30 d.alkaline anion exchange membrane | trans-cyclooctene | block and random copolymer | cross-linked polymer | transmission electron microscopy A lkaline anion exchange membranes (AAEMs) are a class of polymer electrolytes constructed from immobilized cations with hydroxide counteranions (1-3). AAEMs have been widely used for a variety of electrochemical applications, such as redox flow batteries, electrodialysis, and water electrolysis (4-7). One of the most important applications for AAEMs is their use as polyelectrolytes in alkaline exchange membrane fuel cells (AEMFCs). These devices can efficiently convert chemical energy in fuels (e.g., H 2 , hydrazine, and direct alcohols) into electricity. In comparison with proton exchange membrane fuel cells and aqueous alkaline fuel cells, AEMFCs are advantageous because they allow for rapid reduction of oxygen at the cathode, limit fuel cross-over, prevent the formation of carbonate precipitates, and are compatible with nonnoble electrocatalysts (8-12). Because of their essential role in AEMFCs, AAEMs have been extensively studied to optimize their performance and, in particular, to improve their hydroxide conductivity and alkaline stability.Hydroxide conductivity is one of the most important parameters used to evaluate AAEMs, because it is directly related to the ohmic resistance and power density of an AEMFC (9). There are several strategies to enhance the hydroxide conductivity of AAEMs. The most straightforward method is to increase the ion exchange capacity (IEC), such that more ions are present in AAEMs. However, a higher IEC typically results in higher water uptake. While the presence of water facilitates h...

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“…An ideal Young's modulus value can occur over the broad range of~65-450 MPa, where handling was found to be easier according to Ertem et al, no fluid-like behavior was observed, and ruptures due to physical contact were not observed [105]. Below 65 MPa, the membrane can be more fluid-like, and above 450 MPa, the membrane can be very stiff [106,107]. Another important requirement is to keep Young's Modulus difference to a minimum at 25 and 60 • C. Nafion 115 meets these requirements with the values of 288.94 and 221.46 MPa at 25 and 60 • C, respectively.…”

Section: Tensile Strengthmentioning

confidence: 99%

Effect of Increased Ionic Liquid Uptake via Thermal Annealing on Mechanical Properties of Polyimide-Poly(ethylene glycol) Segmented Block Copolymer Membranes

Çiftçioğlu

Frank

2021

Molecules

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Proton exchange membranes (PEMs) suffer performance degradation under certain conditions—temperatures greater than 80 °C, relative humidity less than 50%, and water retention less than 22%. Novel materials are needed that have improved water retention, stability at higher temperatures, flexibility, conductivity, and the ability to function at low humidity. This work focuses on polyimide-poly(ethylene glycol) (PI-PEG) segmented block copolymer (SBC) membranes with high conductivity and mechanical strength. Membranes were prepared with one of two ionic liquids (ILs), either ethylammonium nitrate (EAN) or propylammonium nitrate (PAN), incorporated within the membrane structure to enhance the proton exchange capability. Ionic liquid uptake capacities were compared for two different temperatures, 25 and 60 °C. Then, conductivities were measured for a series of combinations of undoped or doped unannealed and undoped or doped annealed membranes. Stress and strain tests were performed for unannealed and thermally annealed undoped membranes. Later, these experiments were repeated for doped unannealed and thermally annealed. Mechanical and conductivity data were interpreted in the context of prior small angle X-ray scattering (SAXS) studies on similar materials. We have shown that varying the compositions of polyimide-poly(ethylene glycol) (PI-PEG) SBCs allowed the morphology in the system to be tuned. Since polyimides (PI) are made from the condensation of dianhydrides and diamines, this was accomplished using components having different functional groups. Dianhydrides having either fluorinated or oxygenated functional groups and diamines having either fluorinated or oxygenated diamines were used as well as mixtures of these species. Changing the morphology by creating macrophase separation elevated the IL uptake capacities, and in turn, increased their conductivities by a factor of three or more compared to Nafion 115. The stiffness of the membranes synthesized in this work was comparable to Nafion 115 and, thus, sufficient for practical applications.

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Ion transport properties of mechanically stable symmetric ABCBA pentablock copolymers with quaternary ammonium functionalized midblock

Cited by 22 publications

References 61 publications

Water Uptake Study of Anion Exchange Membranes

Water Uptake Study of Anion Exchange Membranes

Highly conductive and chemically stable alkaline anion exchange membranes via ROMP of trans -cyclooctene derivatives

Effect of Increased Ionic Liquid Uptake via Thermal Annealing on Mechanical Properties of Polyimide-Poly(ethylene glycol) Segmented Block Copolymer Membranes

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