講師：Dr. Sanoop Ramachandran (Postdoctoral Researcher, Tokyo Metropolitan University)
題目：Hydrodynamic effects on phase separation in multicomponent membranes
Lipid membranes can be considered to be two-dimensional viscous liquids embedded in a three-dimensional bulk fluid.
In this talk, I will present our work on the effect of the bulk fluid on the dynamics of multicomponent membranes.
Within this theme, I will focus on concentration fluctuations (above Tc) and phase separation (below Tc),
investigated using a combination of theory and simulations.
講師： Didier R. Long
(Laboratoire Polymeres et Materiaux Avances:
CNRS/Rhodia; Rhodia Reserches et Technologies, France)
Slow domains percolation in polymer melts and blends close to the glass transition:
a unifying concept regarding bulk dynamics, dynamics in the vicinity of interfaces,
and the physical properties of nanocomposites
Experiments have demonstrated over past 15 years that the
dynamics in liquids close to and below the glass transition temperature
is strongly heterogeneous, on the scale of a few nanometers. Over the same period,
experiments have demonstrated that the glass transition temperature in the vicinity
of interfaces can be very different from that in the bulk, with shifts either positive
or negative depending on the interaction between the polymer and the interface.
By considering thermally induced density fluctuations in the bulk, we proposed
that the 3-D glass transition is controlled by the percolation of small domains of slow
dynamics, which allows to explain the heterogeneous dynamics close to T_g.
This model allowed then for interpreting a priori unrelated features of polymer dynamics.
We propose that slow domains percolate at a lower temperature in the quasi 2-D
case of thin suspended polymer, corresponding to a glass transition temperature reduction.
In the case of strongly adsorbed films, we show that the strong adsorption
amounts to enhance the slow domains percolation. These effects allow for interpreting the main feature
of confinement effects on the dynamics and in particular for explaining reinforcement properties in
filled elastomers. The model we proposed regarding the glass transition in the bulk
allows then to interpret physical ageing or rejuvenating in van der Waals liquids as the evolution
of the density fluctuations distribution towards the equilibrium one. I will discuss briefly how this model, when extended
to the case of solvent/polymer systems allows for interpreting case II diffusion, which is
how a solvent penetrates and finally melts a glassy polymer matrix.
Regarding these various issues, I will put the emphasis on how percolation of slow domains is key for explaining
their main features.
 D. Long, F. Lequeux,
"Heterogeneous dynamics at the glass transition in van der Waals liquids, in the bulk and in thin films",
EPJ E, 4, 371-387 (2001)
 Souche M., Long D.,
"Case II diffusion and solvent-polymer film drying : a mesoscale model",
EuroPhys. Lett., 77, 48002 (2007)
 Merabia S., Sotta P., Long D.R.,
"A Microscopic Model for the Reinforcement and Non-linear Behavior of Filled
Elastomers and Thermoplastic Elastomers (Payne and the Mullins effects)",
Macromolecules, 41 8252-8266 (2008)