Dynamics of Solvent-free Grafted Nanoparticles
Chremos, Alexandros; Panagiotopoulos, Athanassios; Koch, Donald
The diffusivity and structural relaxation characteristics of oligomer-grafted nanoparticles have been investigated with simulations of a previously proposed coarse-grained model at atmospheric pressure. Solvent-free, polymer-grafted nanoparticles as well as grafted nanoparticles in a melt were compared to a reference system of bare (ungrafted) particles in a melt. Whereas longer chains lead to a larger hydrodynamic radius and lower relative diffusivity for grafted particles in a melt, bulk solvent-free nanoparticles with longer chains have higher relative diffusivities than their short chain counterparts. Solvent-free nanoparticles with short chains undergo a glass transition as indicated by a vanishing diffusivity, diverging structural relaxation time and the formation of body-centered-cubic-like order. Nanoparticles with longer chains exhibit a more gradual increase in the structural relaxation time with decreasing temperature and concomitantly increasing particle volume fraction. The diffusivity of the long chain nanoparticles exhibits a minimum at an intermediate temperature and volume fraction where the polymer brushes of neighboring particles overlap, but must stretch to fill the interparticle space.
The authors would like to thank Professor Fernando Escobedo and Hsiu-Yu Yu for helpful discussions and Professor Escobedo for suggesting the simulation model used in this work. This publication is based on work supported in part by Award No.KUS-C1-018-02, made by King Abdullah University of Science and Technology (KAUST). Additional support was provided by grant CBET-1033155 from the U.S. National Science Foundation (NSF).
The Journal of Chemical Physics
oligomer-grafted nanoparticles; polymer-grafted nanoparticles; nanoparticles with longer chains
Previously Published As
Chremos, Alexandros, Athanassios Z. Panagiotopoulos, and Donald L. Koch. "Dynamics of Solvent-free Grafted Nanoparticles." The Journal of Chemical Physics 136.4 (2012): 044902. Web.