Particle size-induced transition between surface segregation and bulk aggregation in a thin film of athermal polymer-nanoparticle blends

Abstract

Surface segregation and bulk aggregation in a thin film of athermal polymer-nanoparticle blends have been investigated by dissipative particle dynamics simulations. The thin film is confined between two athermal walls and the shape of the nanoparticles is spherical or cubic. Both phases are driven purely by the entropic effect, i.e., depletion attraction, which depends significantly on the nanoparticle size. At a specified particle volume fraction, surface segregation dominates for small nanoparticles but bulk aggregation emerges for large ones. The transition between the two phases is a result of the competition between particle-wall and particle-particle depletion attractions. The dominance of the former leads to surface segregation while the control of the latter results in bulk aggregation. Since nanocubes possess more contact areas and thus exhibit stronger depletion attractions than nanospheres do, the crossover from surface segregation to bulk aggregation occurs at smaller particle size for nanocubes.

Zwitterionic Membrane via Nonsolvent Induced Phase Separation: A Computer Simulation Study

“…The combined results show great agreement with the segregation of the low-surface-energy fluorinated chains to the air/polymer interface. The behavior of the nanoparticle in an athermal polymer system was studied by Teng et al Nanoparticles transited from surface segregation to bulk aggregation as the particle size changes. Recently, Wang et al simulated the NIPS process and explored the influential factors of porous membrane formation .…”

Optical Properties of Nanocomposite Films: Size-tuned vs. Shape-tuned Silver Nanoparticles

“…Such segregation has been previously observed for bidispersed systems, where nanoparticles of different sizes segregate into zones with particles of a single size and zones with particles of mixed sizes [46]. Moreover, it has been predicted that shape of nanoparticle plays a larger role in the segregation of particles in films due to difference in attractive depletion, especially for nanoparticles with flat faces [45].…”

“…This last discrepancy was attributed to the intrinsic uncertainty associated with the preparation of the films. For instance, ultramicrotomed sections from the same film may have different distribution of nanoparticles at different depths [45], and the embedding media causes micrographs of nanoparticles in films to be less clear than the micrographs of nanoparticles in solution. This uncertainty favors the measurement of large nanoparticles.…”

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“…The DPD method has been proven to be an effective mesoscopic simulation tool to study uid events occurring on millisecond timescales and micrometer length scales via tracking the motion of coarsegrained particles (composed of a group of atoms or molecules). Many researchers have studied the morphology of so matter at mesoscopic level using the DPD method, for example, self-assembly of surfactant solutions, [30][31][32] interactions between polymers and nanoparticles 24,33,34 and phase separation for polymer solar cells. [35][36][37] The fundamental equation in the DPD method is Newton's equation of motion.…”