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Internet Electronic Journal of Molecular Design - IEJMD, ISSN 1538-6414, CODEN IEJMAT
| ABSTRACT - Internet Electron. J. Mol. Des. October 2005, Volume 4, Number 10, 721-736 |
Study of the Glass Transition Temperatures of Stereoregular
PMMAs Using Different Force Fields
Armand Soldera and Noureddine Metatla
Internet Electron. J. Mol. Des. 2005, 4, 721-736
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Abstract:
Poly(methyl methacrylate), PMMA, offers a particular regard to the
study of the glass transition since according to the tacticity of its chain,
a different glass temperature transition, Tg, is exhibited. Molecular
modeling is thus a perfect tool to study such a variation since changes
that occur during these transitions can be regarded as differences in
molecular characteristics only. The selection of a forcefield that
correctly depicts this difference is thus of primary importance. In this
article, two forcefields, AMBER and AMBER/OPLS, have been used
to simulate the glass transition of the stereoregular PMMAs. Results
stemming from these simulations are compared with those, already
published, coming from a second generation force field, pcff.
Molecular dynamics simulations are used to study the glass transition
of stereoregular polymers, and their energetic differences, with respect
to the use of two force fields of different generation. Although Tgs are
obtained at higher temperatures than those obtained with the pcff force
field, the difference between the two Tgs is better mimicked using the
AMBER/OPLS force field. The presence of the cross terms in the
force fields is thus not a determining factor in getting the Tgs variation.
A first generation force field could deal with the representation of the
difference in Tgs between stereoregular polymers. Accordingly to the
fact that a first generation force field can deal with the difference in
Tgs difference, a greater amount of phase space could be regarded.
Moreover, studies of specific interaction, such as PMMA behavior
with surfaces, can be undertaken.
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