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The dynamics of a soft particle suspended in a viscous fluid can be changed by the presence of an elastic boundary. Understanding the mechanisms and dynamics of soft–soft surface interactions can provide valuable insights into many important research fields, including biomedical engineering, soft robotics development, and materials science. This work investigates the anomalous transport properties of a soft nanoparticle near a visco-elastic interface, where the particle consists of a polymer assembly in the form of a micelle and the interface is represented by a lipid bilayer membrane. Mesoscopic simulations using a dissipative particle dynamics model are performed to examine the impact of micelle’s proximity to the membrane on its Brownian motion. Two different sizes are considered, which correspond to ≈10−20nm in physical units. The wavelengths typically seen by the largest micelle fall within the range of wavenumbers where the Helfrich model captures fairly well the bilayer mechanical properties. Several independent simulations allowed us to compute the micelle trajectories during an observation time smaller than the diffusive time scale (whose order of magnitude is similar to the membrane relaxation time of the largest wavelengths), this time scale being hardly accessible by experiments. From the probability density function of the micelle normal position with respect to the membrane, it is observed that the position remains close to the starting position during ≈0.05τd (where τd corresponds to the diffusion time), which allowed us to compare the negative excess of mean-square displacement (MSD) to existing theories. In that time range, the MSD exhibits different behaviors along parallel and perpendicular directions. When the micelle is sufficiently close to the bilayer (its initial distance from the bilayer equals approximately twice its gyration radius), the micelle motion becomes quickly subdiffusive in the normal direction. Moreover, the temporal evolution of the micelle MSD excess in the perpendicular direction follows that of a nanoparticle near an elastic membrane. However, in the parallel direction, the MSD excess is rather similar to that of a nanoparticle near a liquid interface.
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Directed assembly of metal nanoparticles in polymer bilayers
The integration of layer-by-layer (LbL) and self-assembly methods has the potential to achieve precision assembly of nanocomposite materials. Knowledge of how nanoparticles move across and within stacked materials is critical for directing nanoparticle assembly. Here, we investigate nanoparticle self-assembly within two different LbL architectures: (1) a bilayer composed of two immiscible polymer thin-films, and (2) a bilayer composed of polymer and graphene that possesses a “hard-soft” interface. Polymer-grafted silver nanocubes (AgNCs) are employed as a model nanoparticle system for systematic experiments – characterizing both assembly rate and resulting morphologies – that examine how assembly is affected by the presence of an interface. We observe that polymer grafts can serve to anchor AgNCs at the bilayer interface and to decrease particle mobility, or can promote particle transfer between layers. We also find that polymer viscosity and polymer mixing parameters can be used as predictors of assembly rate and behavior. These results provide a pathway for designing more complex multilayered nanocomposites.
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- Award ID(s):
- 1636356
- PAR ID:
- 10075260
- Date Published:
- Journal Name:
- Molecular Systems Design & Engineering
- Volume:
- 3
- Issue:
- 2
- ISSN:
- 2058-9689
- Page Range / eLocation ID:
- 390 to 396
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/C7ME00104E
