59 research outputs found
A study for the static properties of symmetric linear multiblock copolymers under poor solvent conditions
We use a standard bead-spring model and molecular dynamics simulations to
study the static properties of symmetric linear multiblock copolymer chains and
their blocks under poor solvent conditions in a dilute solution from the regime
close to theta conditions, where the chains adopt a coil-like formation, to the
poorer solvent regime where the chains collapse obtaining a globular formation
and phase separation between the blocks occurs. We choose interaction
parameters as is done for a standard model, i.e., the Lennard-Jones fluid and
we consider symmetric chains, i.e., the multiblock copolymer consists of an
even number of alternating chemically different A and B blocks of the same
length . We show how usual static properties of the individual
blocks and the whole multiblock chain can reflect the phase behavior of such
macromolecules. Also, how parameters, such as the number of blocks can
affect properties of the individual blocks, when chains are in a poor solvent
for a certain range of . A detailed discussion of the static properties of
these symmetric multiblock copolymers is also given. Our results in combination
with recent simulation results on the behavior of multiblock copolymer chains
provide a complete picture for the behavior of these macromolecules under poor
solvent conditions, at least for this most symmetrical case. Due to the
standard choice of our parameters, our system can be used as a benchmark for
related models, which aim at capturing the basic aspects of the behavior of
various biological systems.Comment: 13 pages, 11 figure
Coalescence of sessile polymer droplets: A molecular dynamics study
Droplet coalescence is ubiquitous in nature and the same time key to various
technologies, such as inkjet printing. Here, we report on the coalescence of
polymer droplets with different chain lengths coalescing on substrates of
different wettability. By means of molecular dynamics simulations of a
coarse-grained model, it is found that the rate of bridge growth is higher in
the case of droplets with smaller contact angles (more wettable substrates) and
decreases with the increase of the chain length of the polymers. Different
behavior has also been identified in the dynamics of the approach of the two
droplets during coalescence with the substrate wettability playing a more
important role compared to the chain length of the polymers. While the dynamics
of the droplet are greatly affected by the latter parameters, the density
profile and flow patterns remain the same for the different cases. Thus, we
anticipate that our work provides further insights into the coalescence of
liquid polymer droplets on solid substrates with implications for relevant
technologies.Comment: 10 pages, 5 figure
Structure of bottle-brush brushes under good solvent conditions. A molecular dynamics study
We report a simulation study for bottle-brush polymers grafted on a rigid
backbone. Using a standard coarse-grained bead-spring model extensive molecular
dynamics simulations for such macromolecules under good solvent conditions are
performed. We consider a broad range of parameters and present numerical
results for the monomer density profile, density of the untethered ends of the
grafted flexible backbones and the correlation function describing the range
that neighboring grafted bottle-brushes are affected by the presence of the
others due to the excluded volume interactions. The end beads of the flexible
backbones of the grafted bottle-brushes do not access the region close to the
rigid backbone due to the presence of the side chains of the grafted
bottle-brush polymers, which stretch further the chains in the radial
directions. Although a number of different correlation lengths exist as a
result of the complex structure of these macromolecules, their properties can
be tuned with high accuracy in good solvents. Moreover, qualitative differences
with "typical" bottle-brushes are discussed. Our results provide a first
approach to characterizing such complex macromolecules with a standard bead
spring model.Comment: To appear in Journal of Physics Condensed Matter (2011
Mixing-Demixing Transition in Polymer-Grafted Spherical Nanoparticles
Polymer-grafted nanoparticles (PGNPs) can provide property profiles than
cannot be obtained individually by polymers or nanoparticles (NPs). Here, we
have studied the mixing--demixing transition of symmetric copolymer melts of
polymer-grafted spherical nanoparticles by means of coarse-grained molecular
dynamics simulation and a theoretical mean-field model. We find that a larger
size of NPs leads to higher stability for given number of grafted chains and
chain length reaching a point where demixing is not possible. Most importantly,
the increase in the number of grafted chains, , can initially favour the
phase separation of PGNPs, but further increase can lead to more difficult
demixing. The reason is the increasing impact of an effective core that forms
as the grafting density of the tethered polymer chains around the NPs
increases. The range and exact values of where this change in behaviour
takes place depends on the NP size and the chain length of the grafted polymer
chains. Our study elucidates the phase behaviour of PGNPs and in particular the
influence of the grafting density on the phase behaviour of the systems
anticipating that it will open new doors in the understanding of these systems
with implications in materials science and medicine.Comment: 6 pages, 4 figures, final version to be published in Soft Matte
Monte Carlo study of the interfacial adsorption of the Blume-Capel model
We investigate the scaling of the interfacial adsorption of the
two-dimensional Blume-Capel model using Monte Carlo simulations. In particular,
we study the finite-size scaling behavior of the interfacial adsorption of the
pure model at both its first- and second-order transition regimes, as well as
at the vicinity of the tricritical point. Our analysis benefits from the
currently existing quite accurate estimates of the relevant (tri)critical-point
locations. In all studied cases, the numerical results verify to a level of
high accuracy the expected scenarios derived from analytic free-energy scaling
arguments. We also investigate the size dependence of the interfacial
adsorption under the presence of quenched bond randomness at the originally
first-order transition regime (disorder-induced continuous transition) and the
relevant self-averaging properties of the system. For this ex-first-order
regime, where strong transient effects are shown to be present, our findings
support the scenario of a non-divergent scaling, similar to that found in the
original second-order transition regime of the pure model.Comment: 6 pages, 5 figures, version published in Phys. Rev. E. arXiv admin
note: text overlap with arXiv:1610.0822
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