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Densely Sulfophenylated Segmented Copoly(arylene ether sulfone) Proton Exchange Membranes

Title
Densely Sulfophenylated Segmented Copoly(arylene ether sulfone) Proton Exchange Membranes
Author
Michael D. Guiver
Keywords
FUEL-CELL APPLICATIONS; MULTIBLOCK COPOLY(ETHER SULFONE)S; POLYMER ELECTROLYTE; ACID GROUPS; SIDE-CHAINS; IONOMERS; SULFONATION; COPOLYMERS; KETONE)S; CONDUCTIVITY
Issue Date
2011-06
Publisher
AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
Citation
MACROMOLECULES, JUN 28 2011, 44 12, p4901-p4910, 10p
Abstract
Segmented copoly(arylene ether sulfone) membranes having densely sulfonated pendent phenyl blocks were synthesized by the coupling reaction of phenoxide-terminated oligomers with bis(4-hydroxyphenyl) sulfone and decafluorobiphenyl (DFBP), followed by postpolymerization sulfonation of the blocks containing pendent phenyl substituents. The coupling reaction was conducted at relatively low temperature by utilizing highly reactive DFBP to prevent any possible trans-etherification that would randomize the hydrophilic hydrophobic sequences. Segmented copolymer molecular weights were reasonably high, as determined by viscosity measurements. Postsulfonation occurred selectively on the pendent phenyl substituent to yield hydrophilic blocks that were highly sulfonated in regular sequence on the linked phenyl rings. The resulting polymers gave transparent, flexible, and tough membranes by solution casting. Morphological observation by transmission electron microscopy (TEM) and atomic force microscopy (AFM) showed that the high local concentration and regular sequence of pendent sulfonic acid groups within the hydrophilic blocks enhanced nanophase separation between the hydrophobic and hydrophilic blocks. A comparison of copolymers with similar ion exchange capacities (IECs) indicated that proton conductivity and water uptake were strongly influenced by the hydrophilic block sequence lengths. Proton conductivity and water uptake increased with increasing block length, even at low relative humidity (RH). The ionomer membrane with X20Y20 (X and Y refer to the number of hydrophilic and hydrophobic repeat units, respectively) and 1.82 mequiv/g of IEC had a proton conductivity of 3.6 x 10(-2) S/cm at 80 degrees C and 50% RH, which is comparable to that of perfluorinated ionomer (Nafion) membrane (4.0 x 10(-2) S/cm).
URI
https://pubs.acs.org/doi/abs/10.1021/ma200937whttp://hdl.handle.net/20.500.11754/36690
ISSN
0024-9297
DOI
10.1021/ma200937w
Appears in Collections:
COLLEGE OF ENGINEERING[S](공과대학) > ENERGY ENGINEERING(에너지공학과) > Articles
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