Multi-Block Copolymers in Selective Solvent: A Brownian Dynamics Simulation

2004 ◽  
Vol 856 ◽  
Author(s):  
Yongsheng Liu ◽  
Huifen Nie ◽  
Rama Bansil ◽  
Zhenli Zhang ◽  
Sharon Glotzer
Keyword(s):  
Brownian Dynamics ◽  
Volume Fraction ◽  
Dynamics Simulation ◽  
Multiblock Copolymers ◽  
Brownian Dynamics Simulation ◽  
Selective Solvent ◽  
Bcc Lattice ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations ◽  
Poor Solvent

ABSTRACTWe performed Brownian Dynamics simulations of multiblock copolymers of A and B polymers in a solvent selective for the A block at a volume fraction of 20%. Tri-, penta- and heptabocks were simulated. Fourier transformation reveals micellar clusters arranged in a BCC lattice, in agreement with scattering experiments. The clusters were analyzed using a percolation approach and we observed larger clusters when the outermost block was in the poor solvent condition. The ratio of number of loops to bridges decreases as the number of blocks in the copolymer increases, as does the polydispersity. Increased penalty of looping as the number of blocks increases leads to a larger number of smaller clusters with more bridges.

Determining the Effective Thermal Conductivity of a Nanofluid Using Brownian Dynamics Simulation

2003 ◽  
Author(s):  
P. Bhattacharya ◽  
S. K. Saha ◽  
A. Yadav ◽  
P. E. Phelan ◽  
R. S. Prasher
Keyword(s):  
Thermal Conductivity ◽  
Brownian Motion ◽  
Effective Thermal Conductivity ◽  
Brownian Dynamics ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Solid Particles ◽  
Dynamics Simulation ◽  
Fluid Viscosity ◽  
Brownian Dynamics Simulation

A nanofluid is a fluid containing suspended solid particles, with sizes of the order of nanometers. Normally the fluid has a low thermal conductivity compared to the suspended particles. Therefore introduction of these particles into the fluid increases the effective thermal conductivity of the system. It is of interest to predict the effective thermal conductivity of such a nanofluid under different conditions like varying particle volume fraction, varying particle size, changing fluid conductivity or changing fluid viscosity, especially since only limited experimental data are available. Also, some controversy exists about the role of Brownian motion in enhancing the nanofluid’s thermal conductivity. We have developed a novel technique to compute the effective thermal conductivity of a nanofluid using Brownian dynamics simulation, which has the advantage of being computationally less expensive than molecular dynamics. We obtain the contribution of the nanoparticles towards the effective thermal conductivity using the equilibrium Green-Kubo method. Then we combine that with the thermal conductivity of the base fluid to obtain the effective thermal conductivity of the nanofluid, and thus are able to show that the Brownian motion contributes greatly to the thermal conductivity.

scholarly journals Self-Assembly of Single-Polymer-Tethered Nanoparticle Amphiphiles upon Varying Tail Length

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2108
Author(s):  
Qingxiao Li ◽  
You-Liang Zhu ◽  
Xinhui Zhang ◽  
Kaidong Xu ◽  
Jina Wang ◽  
...  
Keyword(s):  
Self Assembly ◽  
Brownian Dynamics ◽  
Tail Length ◽  
Selective Solvent ◽  
Hydrophobic Polymer ◽  
System Temperature ◽  
The Rich ◽  
Dynamics Simulations ◽  
Phase Behaviors ◽  
Brownian Dynamics Simulations

We systematically investigated the roles of tail length on the self-assembly of shape amphiphiles composed of a hydrophobic polymer chain (tail) and a hydrophilic nanoparticle in selective solvent using Brownian dynamics simulations. The shape amphiphiles exhibited a variety of self-assembled aggregate morphologies which can be tuned by changing tail length (n) in combination with amphiphile concentration (φ) and system temperature (T*). Specifically, at high φ with T*=1.4, the morphology varied following the sequence “spheres → cylinders → vesicles” upon increasing n, agreeing well with experimental observations. At low φ with T*=1.4 or at high φ with T*=1.2, the morphology sequence becomes “spheres or spheres and cylinders mixture → cylinders → vesicles → spheres” upon increasing n, which has not been found experimentally. Two morphological phase diagrams depending on n and φ were constructed for T*=1.4 and 1.2, respectively. The rich phase behaviors on varying tail length could provide the feasible routes to fabricate target aggregate morphologies in various applications, especially for the vesicles with tunable thickness of membranes that are crucial in drug and gene delivery.

scholarly journals Structure formation in suspensions under uniform electric or magnetic field

2021 ◽  
Author(s):  
Konstantinos Manikas ◽  
Georgios G. Vogiatzis ◽  
Markus Hütter ◽  
Patrick D. Anderson
Keyword(s):  
Magnetic Field ◽  
External Field ◽  
Structure Formation ◽  
Brownian Dynamics ◽  
Volume Fraction ◽  
Structural Evolution ◽  
Thermal Fluctuations ◽  
Branch Points ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

AbstractThe structure formation of particles with induced dipoles dispersed in a viscous fluid, under a spatially and temporarily uniform external electric or magnetic field, is investigated by means of Brownian Dynamics simulations. Dipole–dipole interactions forces, excluded volume forces and thermal fluctuations are accounted for. The resulting structures are characterized in terms of average orientation of their inter-particle vectors (second Legendre polynomial), network structure, size of particle clusters, anisotropy of the gyration tensor of every cluster and existence of (cluster) percolation. The magnitude of the strength of the external field and the volume fraction of particles are varied and the structural evolution of the system is followed in time. The results show that the characteristic timescale calculated from the interaction of only two dipoles is also valid for the collective dynamics of many-particle simulations. In addition, the magnitude of the strength of the external field in the range of values we investigate influences only the magnitude of the deviations around the average behavior. The main characteristics (number density of branch-points and thickness of branches) of the structure are mainly affected by the volume fraction. The possibility of 3D printing these systems is explored. While the paper provides the details about the case of an electric field, all results presented here can be translated directly into the case of a magnetic field and paramagnetic particles.

scholarly journals Dynamical Effective Field Model for Interacting Ferrofluids: II. The proper relaxation time and effects of dynamic correlations

2021 ◽  
Author(s):  
Angbo Fang
Keyword(s):  
Relaxation Time ◽  
Brownian Dynamics ◽  
Field Model ◽  
Volume Fraction ◽  
Effective Field ◽  
Rotational Relaxation ◽  
Dynamic Factor ◽  
Nonadiabatic Effects ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

Abstract The recently proposed dynamical effective field model (DEFM) is quantitatively accurate for ferrofluid dynamics. It is derived in paper I within the framework of dynamical density functional theory (DDFT) along with a phenomenological description of nonadiabatic effects. However, it remains to clarify how the characteristic rotational relaxation time of a dressed particle, denoted by τr, is quantitatively related to that of a bare particle, denoted by τr0. By building macro-micro connections via two different routes, I reveal that under some gentle assumptions τr can be identified with the mean time characterizing long-time rotational self-diffusion. I further introduce two simple but useful integrated correlation factors, describing the effects of quasi-static (adiabatic) and dynamic (nonadiabatic) inter-particle correlations, respectively. In terms of both the dynamic magnetic susceptibility is expressed in an illuminating and elegant form. Remarkably, it shows that the macro-micro connection is established via two successive steps: a dynamical coarse-graining with nonadiabatic effects accounted for by the dynamic factor, followed by equilibrium ensemble averaging captured by the static factor. By analyzing data from Brownian dynamics simulations on monodisperse interacting ferrofluids, I find τr/τr0 is, somehow unexpectedly, insensitive to changes of particle volume fraction. A physical picture is proposed to explain it. Furthermore, an empirical formula is proposed to characterize the dependence of τr/τr0 on dipole-dipole interaction strength. The DEFM supplemented with this formula leads to parameter-free predictions in good agreement with results from Brownian dynamics simulations. The theoretical developments presented in this paper may have important consequences to studies of ferrofluid dynamics in particular and other systems modelled by DDFTs in general.

Brownian Dynamics Simulation of the Dynamics of Stretched DNA

2014 ◽  
Author(s):  
Ikenna D. Ivenso ◽  
Todd D. Lillian
Keyword(s):  
Single Molecule ◽  
Brownian Dynamics ◽  
Magnetic Bead ◽  
Dynamics Simulation ◽  
Coarse Grained ◽  
Brownian Dynamics Simulation ◽  
Dna Molecule ◽  
Flexible Polymer ◽  
Dynamics Simulations ◽  
And Function

DNA is a long flexible polymer and is involved in several fundamental cellular processes such as transcription, replication and chromosome packaging. These processes induce forces and torques in the DNA which deform it. These deformations in turn affect the structure and function of DNA. However, understanding of the dynamic response of DNA to the various forces that act on it is still far from complete. Several experiments have been carried out to study these responses most of which use a micron sized magnetic bead attached to the DNA molecule to both manipulate it and to observe its dynamics. One limitation of this approach is that the dynamics of the DNA molecule has mostly been characterized “indirectly” by observing the dynamics of the magnetic bead. It is also reasonable to expect that, because of the size of the bead relative to that of the DNA, the magnetic bead dynamics will obscure that of the DNA. We adapt existing coarse-grained Brownian dynamics models of DNA to develop a model capable of representing the dynamics of DNA without any of the artifacts inherent to the experiments. This model accounts for bending, torsion, extension, electrostatics, hydrodynamics and the random thermal forces acting on DNA in an electrolyte solution. We then carry out Brownian dynamics simulations with our model to benchmark with well established theoretical results of a stretched polymer in solution. Finally, we employ our model to predict the relaxation time scale for single molecule experiments which sets the framework for future studies in which we plan to further shed light on the dynamics of DNA over long length and time scales.

Sign in / Sign up

Export Citation Format

Share Document