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Mesoscopic simulation of Polymers and Colloids

Mesoscopic simulation of Polymers and Colloids
Mesoscopic simulation of Polymers and Colloids

This thesis reports the application of mesoscale modelling technique to study of the behaviour of complex fluids. We demonstrated their usefulness in the areas where conventional molecular simulation is not applicable due to the size, complexity and long relaxation time of such systems. We gave a brief introduction of two techniques of mesoscopic modelling, the Brownian dynamics method and the dissipative particle dynamics method. Both techniques use the Langevin equation to describe the motion of the particles. The Brownian dynamics method represents the case where the solvent particles can be described implicitly. We simulated colloidal particles immersed in an ionic solution using this technique. The dynamics of the colloidal particles were studied at different ionic strength and suspension density. The simulation showed the formation of aggregates and percolating structures depending on the position of the system in the phase diagram. We studied the local structure evolution after the quench and its relation to the mechanical stability.

In the dissipative particle dynamics, we included the solvent explicitly along with other components in the simulation. The method was used to similar two layers of grafted polymer chains brought into close contact and sheared with respect to each other. We studied the system under different shear rates and observed the shear thinning property of the system. The viscosity was shown to vary at any point relative to the grafting surfaces due to the effect of polymer chains resisting the movement of the solvent particles. We studied the system under varying compression and shown that the off-diagonal and the coefficient was found to be insensitive to the compression but in the absence of solvent, the friction coefficient decreased with decreasing pore width. We also studied the system at different solvent qualities and observed a narrow collapse transition of the layers as the solvent quality was varied from a good to a poor solvent.

University of Southampton
Irfachsyad, Daniel
Irfachsyad, Daniel

Irfachsyad, Daniel (2002) Mesoscopic simulation of Polymers and Colloids. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

This thesis reports the application of mesoscale modelling technique to study of the behaviour of complex fluids. We demonstrated their usefulness in the areas where conventional molecular simulation is not applicable due to the size, complexity and long relaxation time of such systems. We gave a brief introduction of two techniques of mesoscopic modelling, the Brownian dynamics method and the dissipative particle dynamics method. Both techniques use the Langevin equation to describe the motion of the particles. The Brownian dynamics method represents the case where the solvent particles can be described implicitly. We simulated colloidal particles immersed in an ionic solution using this technique. The dynamics of the colloidal particles were studied at different ionic strength and suspension density. The simulation showed the formation of aggregates and percolating structures depending on the position of the system in the phase diagram. We studied the local structure evolution after the quench and its relation to the mechanical stability.

In the dissipative particle dynamics, we included the solvent explicitly along with other components in the simulation. The method was used to similar two layers of grafted polymer chains brought into close contact and sheared with respect to each other. We studied the system under different shear rates and observed the shear thinning property of the system. The viscosity was shown to vary at any point relative to the grafting surfaces due to the effect of polymer chains resisting the movement of the solvent particles. We studied the system under varying compression and shown that the off-diagonal and the coefficient was found to be insensitive to the compression but in the absence of solvent, the friction coefficient decreased with decreasing pore width. We also studied the system at different solvent qualities and observed a narrow collapse transition of the layers as the solvent quality was varied from a good to a poor solvent.

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Published date: 2002

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Local EPrints ID: 464814
URI: http://eprints.soton.ac.uk/id/eprint/464814
PURE UUID: 73b12000-e287-48ed-833f-9793f1ab55de

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Date deposited: 05 Jul 2022 00:03
Last modified: 05 Jul 2022 03:14

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Author: Daniel Irfachsyad

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