Title: Lectures on Modern Approaches to the Physics and Physical Chemistry of Soft Matter
Speaker: Prof.Kenneth S. Schweizer (University of Illinois at Urbana-Champaign)
Venue: Rooma 324, Building of No.2, Wushan Campus
Lesson 1: Glassy Dynamics and Kinetic Arrest in Soft Matter and Materials Science
Time: Wednesday, November 7th, 10:00－15:00
Lesson 2: Dynamics and Viscoelasticity of Entangled Synthetic and Biological Polymer Liquids
Time: Thursday, November 8th, 10:00－15:00
Lesson 3: Structure, Phase Behavior, Dynamics and Mechanical Response in Polymer Nanocomposites
Time: Friday, November 9th, 10:00－15:00
Understanding of the spectacular slowing down of relaxation and mass transport in glass-forming liquids of atoms, molecules, colloids, nanoparticles, polymers and other materials over 14 or more orders of magnitude remains a grand challenge. Moreover, many advanced materials employ amorphous solids, and vitrification can frustrate the assembly of ordered structures. In the first talk, I will present an introductory overview of glassy dynamics from the liquid side describing both the qualitative similarities and large quantitative differences between material classes and even within a single class of compounds (e.g., polymers). The physical ideas, assumptions and limitations of both venerable phenomenological models and more modern approaches will be discussed. In the second talk, I will present our new microscopic, force-based predictive theoretical approach to activated relaxation and emergent elasticity that can address both the physical and chemical aspects of glassy dynamics and kinetic arrest for molecular, colloidal and polymeric systems over the entire range of relevant temperatures and relaxation times. Its generalization to thin films will be briefly mentioned, followed by an in depth discussion of the technologically important problem of penetrant diffusion in supercooled liquids and glasses. Quantitative confrontation of our theories with experiments will be presented throughout the talk. Finally, limitations of our approach and key open questions will be discussed.
The existence and dynamical consequences of topological entanglements between strongly interpenetrating and sufficiently large and/or dense macromolecules of diverse architectures (chains, rods, star-branched) is a fascinating and unique phenomenon in polymer science which is also highly relevant to cell biology. Its fundamental origin is the emergent kinetic consequences of polymer connectivity and uncrossability. In the first talk, I will give an introductory overview of the key features of entangled dynamics, viscoelastic response and diffusion from an experimental perspective. Classic models of unentangled and entangled linear chain and rigid rod liquids will then be described and their predictions compared with experiment. Though existing theories in equilibrium have had many successes, they are highly phenomenological and there remain multiple open fundamental issues especially under strong deformation conditions crucial to polymer processing and internal force mediated processes in biopolymer networks. In the second talk I will present an overview of our recent theoretical work that aims to develop a first principles, force-based, predictive statistical dynamical theory for the quiescent (under isotropic, oriented and confined conditions) and nonequilibrium (strained, stressed) behavior of entangled flexible chain and rigid rod liquids. New predictions will be described from a physical perspective along with quantitative comparisons with experiment and simulation. Open and difficult questions in the area of nonlinear rheology will be briefly discussed, and our recent ideas for making progress sketched.
Polymer nanocomposites (PNC) are typically hybrid organic-inorganic materials that traditionally have combined rigid nanoparticles (diameters 5-200 nm) and flexible macromolecules to achieve unique properties. The classic example is rubber reinforcement via filler particles which is of central importance in the tire industry. However, the field has largely been empirically driven. Over the past decade or two, major progress has been made at formulating and addressing fundamental physical questions concerning these multi-component materials which involve an exceptionally broad range of time, length and energy scales. In the first talk, I will present an overview of the general PNC problem and selected recent contributions by experimentalists, simulators and theorists that address mainly the question of phase behavior and microstructure as a function of chemical and physical variables, and its impact on dynamical properties. In the second talk, I will give an overview of our theoretical efforts over the last decade which have aimed to merge and extend ideas and methods from colloid and polymer physics and physical chemistry to create new predictive and microscopic statistical mechanical theories that address PNC multi-scale structure, states of aggregation, phase separation, nanoparticle diffusion, glass and gel formation, and how nanoparticles modify polymer entanglement phenomena. The new physical ideas will be described along with model calculations and quantitative comparisons with x-ray and neutron scattering, diffusion, structural relaxation, and mechanical measurements.
Ken Schweizer received a B.S. in physics from Drexel University in Philadelphia, and a Ph.D. in physics from the University of Illinois at Urbana-Champaign (UIUC) in 1981 working with the theoretical physical chemist David Chandler. After a postdoc in chemical physics at Bell Labs with Frank Stillinger, in 1983 he joined the Materials Directorate at Sandia National Laboratories where he learned about polymer and materials science. In 1991 he moved to UIUC where he is presently the G. Ronald and Margaret H. Morris Professor of Materials Science and Engineering, Professor of Chemistry, Professor of Chemical and Biomolecular Engineering, and member of the Frederick Seitz Materials Research Laboratory and the Beckman Institute for Advanced Science and Technology. His research interests are centered on developing, and applying to experiment, predictive microscopic statistical mechanical theories of the structure, thermodynamics, phase behavior, dynamics and rheology of diverse soft materials including molecules, polymers, colloids and nanocomposites in the liquid, suspension, crystal, liquid crystalline, thin film, rubber, gel and glass states. Honors include the Dillon Medal, Polymer Physics Prize, and Fellowship from the American Physical Society, the Joel Henry Hildebrand Award in the Theoretical and Experimental Chemistry of Liquids from the American Chemical Society, and the Drucker Eminent Faculty Award and undergraduate and graduate teaching excellence and student mentorship awards from UIUC.
Announced by School of Matreials Science and Engineering