Molecular liquids formed by nanoparticles

Abstract The rheology of a rather special case of molecular nanoliquids formed by polymethylsilsesquioxane nanoparticles which occupy an intermediate position between colloidal particles and macromolecules has been studied. These objects are liquids, homogeneous up to submicron size in a wide temperature range. They demonstrate viscoelastic behavior with very strong dependence of viscosity on molecular weight of these nanoobjects. A new scaling model based on the concept of friction in viscoelastic outer layers describing this kind of behavior has been proposed. Relaxation properties of smaller nanoparticles can be described by a single-mode Maxwell model, while relaxation for larger particles takes place in a wide frequency rage covering three orders. Interpretation of the temperature dependence of viscosity within the framework of the standard WLF equation allowed us to find the “glass” (or gel)transition point. Transition from fluid to global gel-like state was clearly observed at this temperature. As part of finding on the nature of this transition, it was shown that no structural effects are related to this transition and it should be treated as a relaxation phenomenon.