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Title: Poly(terphenylene) Anion Exchange Membranes: The Effect of Backbone Structure on Morphology and Membrane Property

Abstract

A new design concept for ion-conducting polymers in anion exchange membranes (AEMs) fuel cells is proposed based on structural studies and conformational analysis of polymers and their effect on the properties of AEMs. Thermally, chemically, and mechanically stable terphenyl-based polymers with pendant quaternary ammonium alkyl groups were synthesized to investigate the effect of varying the arrangement of the polymer backbone and cation-tethered alkyl chains. The results demonstrate that the microstructure and morphology of these polymeric membranes significantly influence ion conductivity and fuel cell performance. Finally, the results of this study provide new insights that will guide the molecular design of polymer electrolyte materials to improve fuel cell performance.

Authors:
 [1];  [2];  [1];  [1];  [3]; ORCiD logo [1]
  1. Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Chemistry and Chemical Biology
  2. Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Chemistry and Chemical Biology; Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1400128
Report Number(s):
LA-UR-17-22033
Journal ID: ISSN 2161-1653
Grant/Contract Number:
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Macro Letters
Additional Journal Information:
Journal Volume: 6; Journal Issue: 5; Journal ID: ISSN 2161-1653
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Energy Sciences

Citation Formats

Lee, Woo-Hyung, Park, Eun Joo, Han, Junyoung, Shin, Dong Won, Kim, Yu Seung, and Bae, Chulsung. Poly(terphenylene) Anion Exchange Membranes: The Effect of Backbone Structure on Morphology and Membrane Property. United States: N. p., 2017. Web. doi:10.1021/acsmacrolett.7b00148.
Lee, Woo-Hyung, Park, Eun Joo, Han, Junyoung, Shin, Dong Won, Kim, Yu Seung, & Bae, Chulsung. Poly(terphenylene) Anion Exchange Membranes: The Effect of Backbone Structure on Morphology and Membrane Property. United States. doi:10.1021/acsmacrolett.7b00148.
Lee, Woo-Hyung, Park, Eun Joo, Han, Junyoung, Shin, Dong Won, Kim, Yu Seung, and Bae, Chulsung. Fri . "Poly(terphenylene) Anion Exchange Membranes: The Effect of Backbone Structure on Morphology and Membrane Property". United States. doi:10.1021/acsmacrolett.7b00148. https://www.osti.gov/servlets/purl/1400128.
@article{osti_1400128,
title = {Poly(terphenylene) Anion Exchange Membranes: The Effect of Backbone Structure on Morphology and Membrane Property},
author = {Lee, Woo-Hyung and Park, Eun Joo and Han, Junyoung and Shin, Dong Won and Kim, Yu Seung and Bae, Chulsung},
abstractNote = {A new design concept for ion-conducting polymers in anion exchange membranes (AEMs) fuel cells is proposed based on structural studies and conformational analysis of polymers and their effect on the properties of AEMs. Thermally, chemically, and mechanically stable terphenyl-based polymers with pendant quaternary ammonium alkyl groups were synthesized to investigate the effect of varying the arrangement of the polymer backbone and cation-tethered alkyl chains. The results demonstrate that the microstructure and morphology of these polymeric membranes significantly influence ion conductivity and fuel cell performance. Finally, the results of this study provide new insights that will guide the molecular design of polymer electrolyte materials to improve fuel cell performance.},
doi = {10.1021/acsmacrolett.7b00148},
journal = {ACS Macro Letters},
number = 5,
volume = 6,
place = {United States},
year = {Fri May 05 00:00:00 EDT 2017},
month = {Fri May 05 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
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Citation Metrics:
Cited by: 9works
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  • Membranes based on cationic polymers that conduct anions are important for enabling alkaline membrane fuel cells and other solid-state electrochemical devices that operate at high pH. Anion exchange membranes with poly(arylene ether sulfone) backbones are demonstrated by two routes: chloromethylation of commercially available poly(sulfone)s or radical bromination of benzylmethyl moieties in poly(sulfone)s containing tetramethylbisphenol A monomer residues. Polymers with tethered trimethylbenzyl ammonium moieties resulted from conversion of the halomethyl groups by quaternization with trimethyl amine. The water uptake of the chloromethylated polymers was dependent on the type of poly(sulfone) backbone for a given IEC. Bisphenol A-based Udel (R) poly(sulfone) membranesmore » swelled in water to a large extent while membranes from biphenol-based Radel (R) poly(sulfone), a stiffer backbone than Udel, only showed moderate water uptake. The water uptake of cationic poly(sulfone)s was further reduced by synthesizing tetramethylbisphenol A and 4,4-biphenol-containing poly(sulfone) copolymers where the ionic groups were clustered on the tetramethylbisphenol A residues. The conductivity of all samples scaled with the bulk water uptake. The hydration number of the membranes could be increased by casting membranes from the ionic form polymers versus converting the halomethyl form cast polymers to ionic form in the solid state. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1790-1798, 2013« less
  • A poly(2,6 dimethyl 1,4-phenylene oxide)-b-poly(vinyl benzyl) chloride copolymer membranes was processed by solvent casting followed by melt pressing (SCMP) to provide uniformly thin films, 25 +/- 5 mu m, with improved conductivity, mechanical strength, water uptake, dimensional swelling, and chemical stability under 1 M KOH and 80 degrees C. These properties depended strongly on the length of the melt-pressing time. The solvent cast membranes melt pressing time was optimized to provided highly conductive membranes (high OH- conductivity of 75 +/- 25 mS cm(-1) for an IEC of 1.8 mmol g(-1) at room temperature in water). Membranes that were only solventmore » cast and not melt-pressed swelled excessively and had insufficient mechanical integrity for detailed study. When the copolymer powder was melt pressed (without prior solvent casting) at 240 degrees C and ca. 30 MPa for 20 minutes, membranes with high mechanical strength (tensile stress at break of 32 +/- 6 MPa at 25% RH and 29 +/- 3 MPa when 95% RH at 60 degrees C), high conductivity (Cl conductivity of 80 mS/cm at 90 degrees C and 95% RH), and lower water uptake were formed. However, melt pressing alone did not give larger then 5 cm x 5 cm area films, homogeneously thin (< 60 mu m), or mechanical defect-free membranes. The SCMP membranes were uniformly thin, and thermally crosslinked. The mass loss via dehydrochlorination indicated by TGA and elemental analysis confirmed the crosslinking via thermal melt pressing. The SCMP membranes thickness could be reduced by more than 50% (25 +/- 5 mu m) compared to melt pressing alone, and the Cl conductivity increased by 44% at 90 degrees C and 95% RH. The tensile stress at break of the SCMP membranes, however, was reduced by 50% at 25% RH.« less
  • Anion exchange m em branes (AEM )are prom ising solid polym er electrolytes utilized in alkalifuelcells and electrochem icalenergy conversion devices.AEM s m ust ef ciently conductions w hile m aintaining chem icaland m echanicalstability undera range ofoperating conditions.The ionicnature ofAEM sleads to stiffand brittle m em branesunderdry conditions w hile athigher hydrations,w ater sorption causes signi cant softening and w eakening of the m em brane.In this w ork,a new polyethylene-b-poly(vinylbenzyltrim ethylam m onium ) polym er (70 kg/m ol) w as cast into large (300 cm 2),thin (127 3 m ) m em branes.These m em branes exhibitedmore » im proved elasticity over previously tested AEM s,m inim aldim ensional sw elling,and m oderate ionic conductivity (57 2 m S/cm at 50 °C,95% RH in the brom ide form ).Extensional testing indicated a 95% reduction in Young's m odulus betw een dry and hydrated states.Furtherinvestigation ofthe com plex m odulusasa function ofhydration,by dynam ic m echanical analysis,revealed a sharp decrease in m odulusbetw een dry and hydrated states.M echanicalsoftening w as reversible,but the location ofthe transition displayed hysteresis betw een hum idi cation and dehum idi cation.Conductivity increased after m em brane softening;suggesting bulk m echanicalpropertiescan identify thehydration levelrequired forim proved ion transport.Understanding the relationship betw een ion conduction and m echanical properties w illhelp guide AEM developm ent and identify operating conditions for sustained perform ance.« less