The dissipative particle dynamics technique has been used to study grafted polymer chains under shear in solvents of different quality. We show that width of the grafted polymer chains decreases with increasing shear rate for an adsorbed monolayer and bilayer in an athermal solvent but that the layer shrinks in a poor solvent and there is no further decrease in the width on shearing. The polymer chains are preferentially aligned along the direction of the shear and tilted away from the surface normal with even the smallest shear rates. The orientational ordering with respect to the layer director increases with increasing shear. Reducing the quality of the solvent dramatically reduces the width of the grafted layers and the friction between them.

We used Brownian Dynamic simulation to study structural and dynamic properties of bi-disperse colloidal suspensions. The size ratio of large to small particles in the bi-disperse colloidal suspension is set at 5:1 and 10:1. We studied the interaction of aggregates (clusters) formed through DLVO (Derjaguin, Landau, Verwey and Overbeek) and soft sphere interactions in a bi-disperse suspension. The dynamic properties of bi-disperse is correlated by varying the size ratio of bi-disperse particles, it is found that the mobility is decreased at size ratio of large to small particles is 5:1. This is despite the percolating particle gels formation was disrupted by larger particles at higher size ratio.

The form of crystallization colloidal gels is important as matrix for controlled release application. In this work, we use the Brownian Dynamics simulation to study the formation of gels by varying the inverse Debye length. We choose a fixed volume fraction, ϕ = 0.1 and a fixed quenched temperature at room temperature, while the inverse Debye length, κ, is varied. To ensures that the simulations cover the fluid-phase region down to the unstable phase region above the critical coagulation concentration, the inverse Debye length is varied between κ = 120σ−1 to 250σ−1. It shows that at the inverse Debye length κ = 250σ−1 the gel forms by colloidal particles that can support the active ingredient by forming long range network.

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