660
L.A. Ford et al. / Journal of Fluorine Chemistry 126 (2005) 653–660
ꢀ129.46,ꢀ130.12,ꢀ130.72,ꢀ130.97,ꢀ131.30, ꢀ131.48
provide a versatile platform for a new ionomeric materials
useful for fuel cells and other electrochemical applications.
1H NMR d 7.90 (Hb, b), d 7. 36 (Ha, b).
3.9. Copolymerization of Monomers 4a–c (Et4N) to
polymers 8a–c
Acknowledgments
A typical copolymerization was carried out in a 100 mL
roundbottom flask equipped with a mechanical stirrer and a
nitrogen purge. The functionalized monomer 4a–c (Et4N)
was added with unfunctionalized monomer 5 and 1% of
trifunctional monomer 6 in appropriate amounts to obtain
the desired equivalent weights. In a typical run, 1.0 g of 4b
(0.92 mmol), 1.4 g of 5 (4.05 mmol) and 1% of 6
(0.46 mmol) were allowed to react. The reaction vessel
was stirred at 75 rpm and heated to 175 8C for 16 h. Fifty
percent (w/w) of benzonitrile was added to the flask and the
temperature was increased to 210 8C for an additional 24 h.
The benzonitrile was then removed under vacuum
(10ꢀ2 Torr). Upon cooling, the polymer was recovered
and boiled two times in 50% nitric acid for 30 min. The
polymer was then washed with deionized water until neutral
with subsequent boiling in deionized water for 1 h. The
resulting polymer was vacuum dried (10ꢀ2 Torr) at 100 8C
giving an essentially quantitative yield of 8b (1100 equiv.
weight).
We would like to thank Clemson University, 3M
Company and the DOE SC EPSCoR program for financial
support. Dennis Smith acknowledges 3M for a pretenured
faculty award. We also thank Dow Chemical for a generous
donation of, 4,40-(trifluorovinyloxy)biphenyl, and R. Baily
and Dr. W. T. Pennington for X-ray crystallography.
References
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ꢄ 8a (H+) 19F NMR (CD3CN) d ꢀ111.35 (4F, b), d ꢀ118.53
1
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1
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1
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4. Conclusions
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An aryl lithium intermediate containing the trifluorovinyl
ether group was prepared and utilized to obtain a key
sulfonyl chloride starting material. The latter allowed the
synthesis of polymerizable trifluorovinyl aryl ethers contain-
ing the sulfonimide function. Thermal bulk cyclopolymer-
ization of these monomers yielded the first examples of
sulfonimide containing perfluorocyclobutane polymers as
clear, flexible, freestanding films. Analyses of these
polymers show good thermal stability, and conductivities
approaching that of other ionomeric materials, such as
Nafion1. Sulfonimide-containing PFCB polymers clearly
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[19] L.A. Ford, Ph.D. Thesis, Clemson University, 2002.