Chemistry Reference
In-Depth Information
important control variable. We have shown that simulations with predictive power
are already possible, at least in favorable cases, when the effective interaction
parameters of the pure constituents (solvent, oligomer) are adjusted such that
their vapor liquid equilibria are reasonably well described. Interactions between
unlike particles are then described by the Lorentz Berthelot combining rule. We
have shown that dipolar solvents (such as NH
3
) and quadrupolar solvents (such as
supercritical CO
2
) can be described accurately enough by very simple potentials.
However, the described modeling of solvents does not include water, nor does the
described coarse-graining of the macromolecules in terms of very simple bead
spring models apply to proteins or other biopolymers. Also, solutions of synthetic
polyelectrolytes (where one needs to address the effects of counterions and/or salt
ions dissolved in the solution) are completely outside the scope of this article.
Finally, we have addressed only the phase behavior of solutions, and have not
addressed either the structural properties (e.g., as described by the various pair
distribution functions or the size of polymer coils) or the interfacial structure in
phase-separated solutions (though we did pay attention to prediction of the interfa-
cial tension between coexisting phases). Also, the kinetics of phase separation (via
nucleation and growth or spinodal decomposition) has not been discussed. Thus, we
emphasize that, although a few first and promising steps towards the computational
modeling of polymer solutions via computer simulations have been taken, many
further studies are still necessary to obtain a more complete theoretical understand-
ing of polymer solutions and their properties.
Acknowledgement Part of the work reviewed here has been carried out in a fruitful and
productive collaboration with A. Cavallo, V. Ivanov, L. G. MacDowell, M. M¨ ller, M. Oettel,
and T. Strauch; it is a pleasure to thank them. Stimulating discussions with H. Weiss and
F. Heilmann are acknowledged as well. Financial support has been provided by the BASF SE
and by the Deutsche Forschungsgemeinschaft (DFG) in the framework of projects DFG 436 RUS
113/791, PA473/7 1 and PA473/8 1, and Sonderforschungsbereich 625. Computer time grants
were provided by John von Neumann Institute for Computing (NIC) and the Network of Excel
lence SOFTCOMP.
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