Effect of Nanoscale rods on the Kinetics of Phase-Separating Multi-Component Fluids
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Effect of Nanoscale rods on the Kinetics of Phase-Separating Multi-Component Fluids Michael J.A. Hore and Mohamed Laradji1 Physics Department, The University of Memphis, Memphis, TN 38152-3390, USA 1 MEMPHYS-Center for Biomembrane Physics, University of Southern Denmark, DK5230, Denmark ABSTRACT Using large scale particle dynamics simulations, we investigated the effect of nanoscale rods on the dynamics of phase separation dynamics of two-component fluids in three dimensions. We found that when the nanoparticles interact more attractively with one of the two segregating component, they lead to a reduction of the rate of domain growth, and that this decrease is intensified as the nanoparticles volume fraction is increased. Furthermore, our results show that nanorods are much more effective in slowing down the kinetics than nanosphres. The dramatic effect of nanorods on the dynamics of phase separation of multi-component fluids, as opposed to nanospheres, implies that they may be used as an efficacious emulsifying agent of multi-component polymer blends. INTRODUCTION In many advanced applications, novel materials with specific physical properties are desired. With the blending of two or more polymers, materials with tailored mechanical, electrical or optical properties can in principle be achieved. However, the entropy of mixing of polymers is inversely proportional to their molecular weight. Thus, unless the polymers are fairly short, polymer blends tend to unmix. The phase separation of multicomponent polymers can be prevented through the addition of compatibilizers such as diblock copolymers. The surface pressure induced by self-assembled diblock copolymers at the interfaces balances the interfacial tension, which is the driving force of the phase separation phase, leading consequently to single--phase thermodynamically stable micophase--separated structures [1,2]. However, since the synthesis of copolymers is typically expensive, industrial applications of copolymers as compatibilizers have been limited. Alternative compatibilizing agents have therefore been sought after. In particular, nanoparticles have been proposed as an emulsifying agent. Filler particles, such as platelets, elastomers, and fibers are commonly added to single-component polymers in order to improve their mechanical strength, and are widely used in everyday products. Recent studies of spherical nanoparticles in binary fluid mixtures, both in three dimensions [3,4] and in the context of thin films [5-8] have shown that these reduce the growth rate of the dynamics of phase separation. The generic features of the dynamics, however, are the same as in the pure binary fluid. In particular, the mixture undergoes full phase separation, implying therefore that nanospheres may not be considered as an efficient emulsifier of immiscible polymer blends. A natural question that arises is whether the anisotropy of the nanoparticles has an effect on the phase separation dynamics. In the present paper, we report on recent results obtained from large s
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