Structural Transitions of Solvent-Free Oligomer-Grafted Nanoparticles

Novel structural transitions of solvent-free oligomer-grafted nanoparticles are investigated by using molecular dynamics simulations of a coarse-grained bead-spring model. Variations in core size and grafting density lead to self-assembly of the nanoparticles into a variety of distinct structures. At the boundaries between different structures, the nanoparticle systems undergo thermoreversible transitions. This structural behavior, which has not been previously reported, deviates significantly from that of simple liquids. The reversible nature of these transitions in solvent-free conditions offers new ways to control self-assembly of nanoparticles at experimentally accessible conditions.

Figure 1

Radial distribution functions at different densities and temperatures: (a) $D_c=2\sigma$, $f=4$ and 32; (b) $D_c=3\sigma$, $f=2$; (c) $D_c=5\sigma$, $f=64$.

Figure 2

Mean-square displacement of solvent-free oligomer-grafted nanoparticles with $D_c=5\sigma$.

Figure 3

Top: Structural behavior of nanoparticles with $f=4$. Bottom: Structural behavior of nanoparticles with $D_c=5\sigma$. The dashed lines outline the different morphologies, and the dotted lines correspond to systems with the same polymer-bead density ${\rho }_b$.

Figure 4

Structural behavior map of solvent-free oligomer-grafted nanoparticles with fixed chain length $N_m=10$. The dashed lines are approximate boundaries between different behaviors.