Coarse-grain molecular dynamics simulations of nanoparticle-polymer melt: Dispersion vs. agglomeration

TK Patra and JK Singh, JOURNAL OF CHEMICAL PHYSICS, 138, 144901 (2013).

DOI: 10.1063/1.4799265

In this work, we study the influence of polymer chain length (m), based on Lennard-Jones potential, and nanoparticle (NP)-polymer interaction strength (epsilon(np)) on aggregation and dispersion of soft repulsive spherically structured NPs in polymer melt using coarse-grain molecular dynamics simulations. A phase diagram is proposed where transitions between different structures in the NP-polymer system are shown to depend on m and epsilon(np). At a very weak interaction strength epsilon(np) = 0.1, a transition from dispersed state to collapsed state of NPs is found with increasing m, due to the polymer's excluded volume effect. NPs are well dispersed at intermediate interaction strengths (0.5 <= epsilon(np) <= 2.0), independent of m. A transition from dispersion to agglomeration of NPs, at a moderately high NP-polymer interaction strength epsilon(np) = 5.0, for m = 1-30, is identified by a significant decrease in the second virial coefficient, excess entropy, and potential energy, and a sharp increase in the Kirkwood-Buff integral. We also find that NPs undergo the following transitions with increasing m at epsilon(np) >= 5.0: string-like -> branch-like -> sphere-like -> dispersed state. (C) 2013 American Institute of Physics.

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