Condensed Matter and Materials Physics(DCMMP)
Physique de la matière condensée et des matériaux (DPMCM)
Maria KILFOIL
McGill University
Consequences of Being Soft: Equilibrium Concepts in Nonequilibrium, Soft Materials Using Real Space Imaging
'Soft' condensed matter refers to the very small elastic constants -- typically nine to ten orders of magnitude smaller than those of atomic and molecular solids -- conferred to these materials by their large mesoscopic basic building blocks: colloids, polymers, and biomolecules are examples. These materials are easily driven out of equilibrium. They may also be "quenched" to form nonequilibrium structures through the introduction of an interparticle attraction that is strong relative to the thermal energy. One of the unifying aspects of this research is the search for ways to extend well-developed ideas of statistical mechanics to non-equilibrium systems.
In this talk, I will discuss our recent experiments using colloidal systems as models for atoms, and real space imaging for full three-dimensional structure, using this data to measure spatial correlations over time. I will present experimental measurements of translational order in colloidal gels of PMMA colloids with polymer added to induce a controlled attraction. These results are the first to quantify the microscopic disorder in non-equilibrium solids using model colloidal systems. In doing so, I will introduce a new translational order parameter that is sensitive to long range order in these non-random packings, and should be sensitive to a changing characteristic length scale with age, and, importantly, is also sensitive to anisotropy. I will further show the first experimental measurements of the equation of state in a system with short range attractions using the same colloid-polymer model system.