An n.m.r. study of absorbed water in polybenzimidazole

Brooks, N. W. J.; Duckett, R. A.; Rose, J.; Ward, I. M.; Clements, J.

doi:10.1016/0032-3861(93)90664-v

Cited by 77 publications

(86 citation statements)

References 5 publications

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“…By immersing a dry PBI membrane in distilled water at room temperature, up to 15-19 wt% of water can be absorbed, corresponding to about 3 water molecules per repeat unit of PBI. The water uptake is due to intermolecular hydrogen bonding between water and N and N-H groups in the PBI [188,189]. In case of acid-doped membranes at an acid-doping level of up to 2 mole H 3 PO 4 per PBI unit, the water uptake is lower than that for the pristine PBI [188].…”

Section: Water Uptake and Acid Dopingmentioning

confidence: 95%

“…The infrared (IR) [30,31,[181][182][183][184][185][186][187][188], Raman spectroscopy [187][188][189] and nuclear magnetic resonance (NMR) spectra [181,182,186] have been made to investigate the polymer and its protonation by acids. For pristine PBI, the IR spectrum [183][184][185] from 2000 to 4000 cm −1 is of particular interest since most of the informative N-H stretching modes occur in this range, with typically three distinguishable bands at 3415, 3145 and 3063 cm −1 .…”

Section: Spectroscopic Studiesmentioning

confidence: 99%

“…Raman spectra of PBI [187][188][189] and acid-doped PBI [187,188] have been studied. The FT-Raman band at 1000 cm −1 was assigned to the meta-benzene ring vibration, unchanged after the acid doping.…”

Section: Spectroscopic Studiesmentioning

confidence: 99%

See 2 more Smart Citations

High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

Jensen

Savinell

et al. 2009

Progress in Polymer Science

1,235

852

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This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. To achieve high temperature operation of proton exchange membrane fuel cells (PEMFC), preferably under ambient pressure, acid-base polymer membranes represent an effective approach. The phosphoric acid-doped polybenzimidazole membrane seems so far the most successful system in the field. It has in recent years motivated extensive research activities with great progress. This treatise is devoted to updating the development, covering polymer synthesis, membrane casting, physicochemical characterizations and fuel cell technologies. To optimize the membrane properties, high molecular weight polymers with synthetically modified or N-substituted structures have been synthesized. Techniques for membrane casting from organic solutions and directly from acid solutions have been developed. Ionic and covalent cross-linking as well as inorganic-organic composites has been explored. Membrane characterizations have been made including spectroscopy, water uptake and acid doping, thermal and oxidative stability, conductivity, electro-osmotic water drag, methanol crossover, solubility and permeability of gases, and oxygen reduction kinetics. Related fuel cell technologies such as electrode and MEA fabrication have been developed and high temperature PEMFC has been successfully demonstrated at temperatures of up to 200• C under ambient pressure. No gas humidification is mandatory, which enables the elimination of the complicated humidification system, compared with Nafion cells. Other operating features of the PBI cell include easy control of air flow rate, cell temperature and cooling. The PBI cell operating at above 150• C can tolerate up to 1% CO and 10 ppm SO 2 in the fuel stream, allowing for simplification of the fuel processing system and possible integration of the fuel cell stack with fuel processing units. Long-term durability with a degradation rate of 5 V h −1 has been achieved under continuous operation with hydrogen and air at 150-160• C. With load or thermal cycling, a performance loss of 300 V per cycle or 40 V h −1 per operating hour was observed. Further improvement should be done by, e.g. optimizing the thermal and chemical stability of the polymer, acid-base interaction and acid management, activity and stability of catalyst and more importantly the catalyst support, as well as the integral interface between electrode and membrane.

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Section: Water Uptake and Acid Dopingmentioning

confidence: 95%

Section: Spectroscopic Studiesmentioning

confidence: 99%

See 1 more Smart Citation

High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

Jensen

Savinell

et al. 2009

Progress in Polymer Science

1,235

852

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“…Ionization of the polymer further promoted this mechanism due to the released intermolecular hydrogen bonding, which is otherwise responsible for the mechanical strength of the pristine material. When the concentration of the bulk solution was increased After drying at 150 °C for 3 h, the strong broad -OH band (2300-3700 cm -1 ) due to water could no longer be observed and the characteristic absorption band at 3415 cm -1 due to free N-H stretching [4,59] became visible for the pristine m-PBI (Figure 6b). At higher KOH concentrations than 15 wt.% the N-H stretching band disappeared.…”

Section: Figurementioning

confidence: 99%

“…Poly(2,2'-(m-phenylene)-5,5'-bisbenzimidazole) (m-PBI, Figure 1) is the most widely used derivative and it is synthesized by melt condensation polymerization [2] or more commonly by homogenous solution polymerization in polyphosphoric acid [3] from 3,3'-diaminobenzidine and isophthalic acid. It is a highly hygroscopic polymer, showing water uptake typically around 15 wt.% [4], corresponding to about 3 water molecules per polymer repeat unit. It strongly interacts with ionic species [5], and the imidazole moieties are readily protonated in the presence of protic acids ( Figure 1, top) to give polymer matrices with high proton conductivity [6].…”

Section: Introductionmentioning

confidence: 99%

Understanding ternary poly(potassium benzimidazolide)-based polymer electrolytes

Aili

Jankova

Han

et al. 2016

Polymer

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A qualitative evaluation of water and monomethyl hydrazine in ethylcellulose membrane

Ravindra

Rao

Khan

1999

J. Appl. Polym. Sci.

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Specific interaction sites of ethylcellulose (EC) with water and monomethyl hydrazine (MMH) and its hydrate have been studied by Fourier transform infrared spectra. Measurements of diffusion and sorption coefficients of MMH and water in EC were made from the reduced sorption curves to determine the overall selectivity of the membrane. Flow patterns across the membrane were examined under an optical microscope (OM) equipped with a differential interference contrast (DIC) facility. Correlation of the front velocity and the diffusivity has been used to calculate and compare these values of diffusion coefficient with that obtained from reduced sorption curve. Desorption of MMH hydrate from EC has been attributed to polymer relaxation phenomena. The physical aging process of the membrane has been monitored by FTIR analysis and mechanical strength evaluation. These studies showed that the EC membrane can be used for prolonged periods in MMH and, as such, is suitable for the separation of MMH-water solutions.

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An n.m.r. study of absorbed water in polybenzimidazole

Cited by 77 publications

References 5 publications

High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

Understanding ternary poly(potassium benzimidazolide)-based polymer electrolytes

A qualitative evaluation of water and monomethyl hydrazine in ethylcellulose membrane

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