Dynamics of nanoparticles in polydisperse polymer networks: From free diffusion to hopping

Condensed Matter lunchtime seminar

Dynamics of nanoparticles in polydisperse polymer networks: From free diffusion to hopping

  • Event time: 1:00pm
  • Event date: 21st September 2021
  • Speaker: Valerio Sorichetti (Paris-Saclay University)
  • Location: Zoom - see email invite.

Event details

Using molecular dynamics simulations we study the static and dynamic properties of spherical nanoparticles (NPs) embedded in a disordered and polydisperse polymer network. Purely repulsive (RNP) as well as weakly attractive (ANP) polymer-NP interactions are considered. It is found that for both types of particles the NP dynamics at intermediate and at long times is controlled by the confinement parameter C=σN/λ, where σN is the NP diameter and λ is the dynamic localization length of the crosslinks. Three dynamical regimes are identified: i) For weak confinement (C≲1) the NPs can freely diffuse through the mesh; ii) For strong confinement (C≳1) NPs proceed by means of activated hopping; iii) For extreme confinement (C≳3) the mean squared displacement shows on intermediate time scales a quasi-plateau since the NPs are trapped by the mesh for very long times. Escaping from this local cage is a process that depends strongly on the local environment, thus giving rise to an extremely heterogeneous relaxation dynamics. The simulation data are compared with the two main theories for the diffusion process of NPs in gels. Both theories give a very good description of the C−dependence of the NP diffusion constant, but fail to reproduce the heterogeneous dynamics at intermediate time scales.

About Condensed Matter lunchtime seminars

This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..

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