Polymer-grafted nanoparticles (PGNPs) can provide property profiles than
cannot be obtained individually by polymers or nanoparticles (NPs). Here, we
have studied the mixing--demixing transition of symmetric copolymer melts of
polymer-grafted spherical nanoparticles by means of coarse-grained molecular
dynamics simulation and a theoretical mean-field model. We find that a larger
size of NPs leads to higher stability for given number of grafted chains and
chain length reaching a point where demixing is not possible. Most importantly,
the increase in the number of grafted chains, Ngâ, can initially favour the
phase separation of PGNPs, but further increase can lead to more difficult
demixing. The reason is the increasing impact of an effective core that forms
as the grafting density of the tethered polymer chains around the NPs
increases. The range and exact values of Ngâ where this change in behaviour
takes place depends on the NP size and the chain length of the grafted polymer
chains. Our study elucidates the phase behaviour of PGNPs and in particular the
influence of the grafting density on the phase behaviour of the systems
anticipating that it will open new doors in the understanding of these systems
with implications in materials science and medicine.Comment: 6 pages, 4 figures, final version to be published in Soft Matte