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meet the results of this study, which showed an increase in
the degree of conversion when piperonyl alcohol was used
in the photoinitiation system (Disilox and Polysilox) when
compared with the control.
monomers have totally different behavior of polymerization
depending on their chemical structure.
ACKNOWLEDGMENTS
Furthermore, the addition of an alcohol to an epoxide system
can also affect the cationic polymerization through the chain
transfer reaction. A hydroxyl group attacks the oxiranium ion
end of the growing polymer chain to form an ether bond
and cause the release of a proton, and the released proton
can initiate the growth of the next polymer chain.22 Olsson
et al. found that the presence of a small amount of a diol
(hexanediol) led to an increase in the photoinitiated cationic
polymerization, and they explained that the reason for this
was that the alcohol could act as a catalyst for the formation
of the superacid to initiate the polymerization.23 This can
explain the increase in the degree of conversion in the pho-
toinitiators system with 1,2 ethanediol. Wang et al. observed
that the extent of crosslinking and the degree of conversion
could be controlled by adjusting the proton concentration
through variation of the structure of diol molecule present in
the polymerization system; as such, one could conveniently
modify the properties of an epoxy resin.24
The authors thank Cesar Liberato Petzhold (Federal University
of Rio Grande do Sul) for providing the DSC-PCA equipment
and CNPq and FAPERGS/Brazil for the scholarship.
REFERENCES AND NOTES
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The different molecular structure and the yield of the
siloxane-oxirane monomers synthesized affect the polymer-
ization reaction, which can be observed through the diffi-
culty of measuring the degree of conversion of the Polysilox
monomer, which presented a low yield (55%). The unreacted
monomers and the repetition of the elementary unit, with a
high molecular weight (low mobility) and a low concentra-
tion of reactive groups per gram when compared with Cyclo-
silox and Disilox, could explain the results.
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use in dental polymers used in this study was shown to be
effective. The combination of monomers with different
molecular structures can improve the properties of the poly-
mer formed. This new class of monomers could be a way to
develop dental materials that eliminate the problems pro-
moted for the polymerization shrinkage and the resulting
stress, decreasing the dentists’ concern with the technique
applied during the clinical procedure. New studies about the
biological implications, mechanical properties, and improve-
ments in the polymerization of the siloxane-oxirane mono-
mers must be conducted.
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CONCLUSIONS
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This study showed a simple and effective way to synthesize
siloxane-oxirane monomers with a high potential for applica-
tion in dental materials. Furthermore, the presence of etha-
nediol is essential to achieve clinically relevant
polymerization conversion and the new siloxane-oxirane
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orimetry 2004, 76, 367–377.
24 Z. G. Wang, X. B. Lin, W. S. Liu, Polym. Int. 2009, 58, 74–
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