# (423c) Effects of Matrix Chain Length on Miscibility of Nanoparticles

- Conference: AIChE Annual Meeting
- Year: 2018
- Proceeding: 2018 AIChE Annual Meeting
- Group: Nanoscale Science and Engineering Forum
- Session:
- Time:
Tuesday, October 30, 2018 - 4:06pm-4:24pm

polymer matrices/melts. The grafting of chemically similar polymer chains to the nanofiller has

been a commonly proposed solution. However, aggregation of filler particles remains a problem.

Furthermore, the particle aggregation observed experimentally by decreasing the graft/matrix

chain ratio (N/M) remains unobservable in simulations of a single nanoparticle (NP) in a ho-

mopolymer matrix. Here, molecular dynamics simulations were used to study the miscibility

effects of decreasing the ratio N/M on a polymer grafted nanoparticle in a polymer melt. The

polymer matrix chain length was varied systematically in a series of simulations , while NP

radius, grafting density, and grafted chain length were held constant. We first show that com-

position profiles of graft/matrix chains do not reveal any signs of brush collapse, observed

experimentally, with increasing matrix chain length. The brush heights were then calculated

using a second moment of the segment density and only highlighted a good to theta solvent

transition. As most of the differences in segment density are evident closer to the surface of the

nanoparticle, we thus conjecture that the first solvation shell, defined as the region bounding

the first peak of the radial distribution function of monomers around the NP, might be more

illuminating. Indeed, an analysis of the monomer fluctuations in the first solvation shell reveals

several findings: (1) Miscibility effects by the matrix on the polymer grafted NP can be observed

in the first solvation shell, (2) The matrix chains rather than the graft chains might give more

insight into any conformational changes in the brush, (3) there is a subtle hint of a second

transition at a N/M ratio of âˆ¼ 0.3 . These results imply that the interactions at

the surface, perhaps between the NP itself and the melt, are significant in studying changes in

miscibility of the polymer grafted NP and might be driving the morphology of the entire brush.

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