6 research outputs found
Coarse-graining and phase behavior of model star polymer-colloid mixtures in solvents of varying quality
We study the effective interactions and phase behavior of star polymer-colloid mixtures through theory and Monte Carlo simulations. We extend previous theoretical approaches for calculating the effective star-colloid pair potential to take into account attractive contributions, which become significant at worsening solvent conditions. In order to assess the validity of our simulation and theory, we compute the effective interactions via virtual move parallel tempering Monte Carlo simulations using a microscopic bead-spring model for the star polymer and achieve excellent agreement. Finally, we perform grand canonical Monte Carlo simulations of the coarse-grained systems to study the effect of solvent quality on the phase behavior
Bottom-Up Colloidal Crystal Assembly with a Twist
Globally
ordered colloidal crystal lattices have broad utility
in a wide range of optical and catalytic devices, for example, as
photonic band gap materials. However, the self-assembly of stereospecific
structures is often confounded by polymorphism. Small free-energy
differences often characterize ensembles of different structures,
making it difficult to produce a single morphology at will. Current
techniques to handle this problem adopt one of two approaches: that
of the âtop-downâ or âbottom-upâ methodology,
whereby structures are engineered starting from the largest or smallest
relevant length scales, respectively. However, recently, a third approach
for directing high fidelity assembly of colloidal crystals has been
suggested which relies on the introduction of polymer cosolutes into
the crystal phase [Mahynski, N.; Panagiotopoulos, A. Z.; Meng, D.;
Kumar, S. K. <i>Nat. Commun.</i> <b>2014</b>, <i>5</i>, 4472]. By tuning the polymerâs morphology to interact
uniquely with the void symmetry of a single desired crystal, the entropy
loss associated with polymer confinement has been shown to strongly
bias the formation of that phase. However, previously, this approach
has only been demonstrated in the limiting case of close-packed crystals.
Here, we show how this approach may be generalized and extended to
complex open crystals, illustrating the utility of this âstructure-directing
agentâ paradigm in engineering the nanoscale structure of ordered
colloidal materials. The high degree of transferability of this paradigmâs
basic principles between relatively simple crystals and more complex
ones suggests that this represents a valuable addition to presently
known self-assembly techniques
How to simulate patchy particlesâ
Abstract.: Patchy particles is the name given to a large class of systems of mesoscopic particles characterized by a repulsive core and a discrete number of short-range and highly directional interaction sites. Numerical simulations have contributed significantly to our understanding of the behaviour of patchy particles, but, although simple in principle, advanced simulation techniques are often required to sample the low temperatures and long time-scales associated with their self-assembly behaviour. In this work we review the most popular simulation techniques that have been used to study patchy particles, with a special focus on Monte Carlo methods. We cover many of the tools required to simulate patchy systems, from interaction potentials to biased moves, cluster moves, and free-energy methods. The review is complemented by an educationally oriented Monte Carlo computer code that implements all the techniques described in the text to simulate a well-known tetrahedral patchy particle model. Graphical abstract: [Figure not available: see fulltext.]