Conveners
(DCMMP) M3-6 Soft Condensed Matter III | Matière condensée molle III (DPMCM)
- John Dutcher
Glass-formers represent an important family of natural and manufactured materials ubiquitous in nature, technology, and our daily lives. Approaching their glass transition temperatures ($T_g$) makes them resemble solids lacking long-range structural order, similar to liquids. Careful detection of the glass transition and accurate measurement of the $T_g$-value constitute fundamental steps in...
We are studying stable polystyrene (PS) glasses prepared by PVD (physical vapour deposition) with N up to ~12. These glasses have fictive temperatures as low as Tg -20 K with respect to its supercooled liquid line, and a kinetic stability of down to deposition temperatures of ~ 0.84*Tg. Employing increased surface dynamics, vapour deposition can yield an effectively packed amorphous material...
We measure the isothermal rejuvenation of stable glass films of poly(styrene) and poly(methylmethacrylate). We demonstrate that the propagation of the front responsible for the transformation to a supercooled-liquid state can serve as a highly localized probe of the local supercooled dynamics. We use this connection to probe the depth-dependent relaxation rate with nanometric precision for a...
When continuum materials with cohesive forces are perturbed from an equilibrium configuration, they relax over time tending toward the lowest energy shape. We are interested in studying the physics of a similar ageing process in a two-dimensional granular system in which individual particle rearrangements can be directly observed. We present an experiment in which a two-dimensional raft of...
Granular systems can be great analogies to the molecular structures of materials and introducing an intruder to the system can provide novel insight into their dynamics. Here, we study the response of a disordered bi-disperse two-dimensional aggregate of oil droplets to a moving ferrofluid droplet which acts as a controlled intruder. The frictionless and cohesive oil droplets form a compact...
Collective properties of granular materials are determined by both interparticle forces and packing fraction. The conical shape of piles of granular material, like a pile of sand is dependant on the interparticle friction and is characterized by the angle of repose of the pile. Surprisingly, we observe formation of conical piles for aggregates of frictionless particles. Our model system is...
