Prix Professeur René Wasserman 2011 - Gianluca Ambrosetti

"Pour son approche originale à la compréhension et description des propriétés de transport électronique dans les nanocomposites polymères, et pour l'apport novateur au problème général de la transition conducteur-isolant dans les matériaux composites".

On the insulator-conductor transition in polymer nanocomposites.

Polymeric organic materials, more commonly called plastics, are well known for their generally excellent behavior as electric insulators. Less known is the fact that polymers, alone or in combination with additives, can offer conductivities which come close to that of metals.
An important example of this kind of materials are conductive polymer nanocomposites, which consist in more or less random dispersions of nanometric conductive fillers like carbon nanotubes, nanofibers or graphene sheets in a polymer matrix.

Here, we present an investigation of the models describing the electrical conductivity of polymer nanocomposites, with an emphasis on its dependence on the filler concentration and geometry.
The investigation is carried out mainly through ``bottom-up'' simulations with algorithms replicating the main microscopic features of the composites, including a realistic electron tunneling inter-particle conduction mechanism.
These studies, through the identification of scaling laws and universal behavior, lead to simple semi-empirical relations which allow a precise estimation of the composite conductivity from few microscopic parameters.