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1
sharp peak at 1717 cm21. In addition, in the H NMR spectrum
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of PMMA after reaction with 2-ethylhexylamine in the presence
of TZ and DBU, a distinct peak owing to 2-ethylhexyl protons
was observed in the region from 0.7 to 1.2 ppm, which clearly
showed a successful installation of amines via amidation reac-
tion, demonstrating that the amidation reaction of PMMA
indeed took place at carbonyl group (Fig. 7). Thus, the ulti-
mately stable ester moieties in PMMA were revealed to behave
as a facile polymeric activated ester in the presence of the DBU
and TZ catalytic system. In a clear contrast to the reaction in
the presence of organo-activators, only 19.6% of methyl esters
of PMMA were consumed, showing a very limited reactivity of
PMMA for the reaction in the absence of activators (Table 1,
run 9).
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This new chemical modification method should lead to new
synthetic functionalization possibilities for the common polymer
PMMA and thereby enhance the applications of PMMA within
biomedical applications. In addition, synthesis of stereo-
controlled polymethacrylamides is a long-lasting challenge in
polymer synthesis and the herein presented synthetic methods
opens a route to master this challenge. Starting from stereo-
controlled polymethacrylates—whose synthetic protocols are
rather established as compared with polymethacryla-
mides29,30—preparation of stereo-controlled polymethacryla-
mides should be straightforward and is currently under
investigation.
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CONCLUSIONS
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In this study, we succeeded in the activation of nonactivated
ester moieties embedded in polymer structures. Although
PPFPMA was allowed to react with amines in the presence
of proton scavenger such as NEt3, PPhMA did not react with
amines in the presence of NEt3. However, the combination of
1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 1,2,4-triazole
(TZ) yielded facile conversion from ester to amide for
PPhMA with almost perfect conversion. In addition, under
the same conditions as PPhMA, PTFEMA, and PMMA under-
went amidation in the presence of the organo-activating
agents, resulting in impressive degrees of conversion
(>70%). To the best of our knowledge, this is the first
report on using PMMA as a facile activatable ester precursor
polymer for the synthesis of functionalized poly(methacryla-
mides) by using organo-activating method.
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23 N. K. Singha, M. I. Gibson, B. P. Koiry, M. Danial, H.-A. Klok,
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28 Although the structure of the imide derivatives in polymers
practically can not be precisely assigned, cyclic 6-membered
ring should be the most probable structure because of thermal
stability. In addition, though precise determination of structural
compositions requires quantitative measurements, preliminary
speculation of imide generation ratio was given by using
IR measurements ignoring the difference in absorption
coefficiency of amides, esters, and imides due to their struc-
tural simirality.
ACKNOWLEDGMENTS
R. Kakuchi gratefully acknowledges the support by a Grant-
in-Aid for the Japan Society for the Promotion of Science
(JSPS) Fellows.
REFERENCES AND NOTES
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