137 research outputs found
Fluctuation effects in ternary AB+A+B polymeric emulsions
We present a Monte Carlo approach to incorporating the effect of thermal
fluctuations in field theories of polymeric fluids. This method is applied to a
field-theoretic model of a ternary blend of AB diblock copolymers with A and B
homopolymers. We find a shift in the line of order-disorder transitions from
their mean-field values, as well as strong signatures of the existence of a
bicontinuous microemulsion phase in the vicinity of the mean-field Lifshitz
critical point. This is in qualitative agreement with a recent series of
experiments conducted with various three-dimensional realizations of this model
system. Further, we also compare our results and the performance of the
presently proposed simulation method to that of an alternative method involving
the integration of complex Langevin dynamical equations.Comment: minor changes, references adde
A generic model for lipid monolayers, bilayers, and membranes
We describe a simple coarse-grained model which is suited to study lipid
layers and their phase transitions. Lipids are modeled by short semiflexible
chains of beads with a solvophilic head and a solvophobic tail component. They
are forced to self-assemble into bilayers by a computationally cheap `phantom
solvent' environment. The model reproduces the most important phases and phase
transitions of monolayers and bilayers. Technical issues such as Monte Carlo
parallelization schemes are briefly discussed.Comment: 4 pages, 4 figures conference paper for the CCP 2006 (Gyeongju,
Korea
Phase Behaviour of Amphiphilic Monolayers: Theory and Simulation
Coarse grained models of monolayers of amphiphiles (Langmuir monolayers) have
been studied theoretically and by computer simulations. We discuss some of the
insights obtained with this approach, and present new simulation results which
show that idealised models can successfully reproduce essential aspects of the
generic phase behaviour of Langmuir monolayers.Comment: To appear in J. Phys.: Cond. Matte
A Simple Computer Model for Liquid Lipid Bilayers
We present a simple coarse-grained bead-and-spring model for lipid bilayers.
The system has been developed to reproduce the main (gel-liquid) transition of
biological membranes on intermediate length scales of a couple of nanometres
and is very efficient from a computational point of view. For the solvent
environment, two different models are proposed. The first model forces the
lipids to form bilayers by confining their heads in two parallel planes. In the
second model, the bilayer is stabilised by a surrounding gas of "phantom"
solvent beads, which do not interact with each other. This model takes only
slightly more computing time than the first one, while retaining the full
membrane flexibility. We calculate the liquid-gel phase boundaries for both
models and find that they are very similar.Comment: 11 pages, 6 figure
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