Nanocomposites under flow: dispersing nanoparticle assemblies in polymer melts
Prof. Dr. Dimitris Vlassopoulos
FORTH and Universtiy of Crete, Department of Materials Science and Technology, Heraklion, Greece
- 02.Apr.2014 11:00
- 02.Apr.2014 12:00
- Seminarraum A1-A3, Building 04.6
Grafted nanoparticles in homopolymer melts represent a much-studied model nanocomposite system. It has been shown that the grafting density and size of grafted chains affect the nanoparticle dispersion and in particular the formation of various metastable (depending on the nature of the matrix) self-assembled morphologies, which are nonetheless robust and tunable. An open question, which we address partly here, is whether flow can promote mixing of the nanoparticles or not. Specifically, we explore the effects of shear flow on nanoparticle morphologies (silica particles grafted with polystyrene in polystyrene matrix) and find that, within the experimentally accessible range of rates, it is not possible to fully disperse the nanoparticles, presumably due to the dominance of interparticle attractions over flow fields and thermal energy. A connection to the flow of (non-Brownian) particles in viscoelastic media and the yielding of colloidal gels is attempted.
Work in collaboration with S. Kumar (Columbia), R. H. Colby (Penn State) and B. C. Benicewicz (South Carolina).
Fax: +49 2461 61-2280