Polymer-grafted nanoparticles (PGNs) are usually synthesized and processed in solution before creating solid systems with uniform spacings of inorganic particles in robust and flexible organic matrices, which are of interest for applications such as hybrid electronics, sensors, dielectrics, and flexible energy storage devices. Understanding interparticle interactions in solvated PGN systems is crucial to control the structure of PGNs during deposition. We use coarse-grained molecular dynamics (MD) simulations to investigate the effective interactions between pairs of PGNs in implicit solvents. Specifically, we use a standard Kremer-Grest model for graft polymer chains, which are rigidly attached to spherical nanoparticles. The nanoparticle beads are ten times the size of the monomer beads. Monomers interact via mixed Lennard-Jones potentials in which the repulsive portions are kept constant while the strength of the attractive portions is adjusted to consider solvents of various qualities. Nanoparticle interactions are of an integrated form as though they are comprised of a melt of monomers of uniform density. We analyze polymer conformations around isolated and interacting pairs of PGNs immersed in implicit solvents of different strengths. In both cases, the monomers in the canopies rapidly collapse onto the nanoparticles as solvent strength increases. We calculate the potentials of mean force (PMFs) between the PGNs and find a relatively sudden onset of a deep attractive well with increasing solvent strength, corresponding to greater overlaps of canopies. The implications for solution phase behavior will be discussed.

Studying interactions between solvated polymer-grafted nanoparticles via coarse-grained molecular dynamics simulations

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