Using Confinement to Study the Colloidal Glass Transition

Emory University, Atlanta GA

Investigators

Abstract

****NON-TECHNICAL ABSTRACT**** Recent advances in nanotechnology have discovered that some materials behave differently on a very small scale. For example, smaller objects are easier to break than larger objects; but small pieces of plastic less than 100 nanometers thick are even easier to break than would be expected by extrapolating from what we know about thicker pieces of plastic. Plastics are amorphous materials, similar to window glass, and now it is known that many glassy materials behave differently in small enough samples. However, some become stronger and some become weaker. This individual investigator award supports experiments to study a model system of small plastic particles in a liquid, which behaves analogously to a glass when the particle concentration is increased. The experiments will use a microscope to view the motion of the particles and see how this motion changes when the sample is confined between two closely spaced parallel glass plates. In this way, how the system depends on the spacing between the plates will be directly observed. This research is important for future nanotechnology applications that rely on tiny structures built out of glassy materials such as plastic. This project provides training and education for both undergraduate and graduate students. Additionally, the laboratory will conduct at least one field trip each year for groups of high school school students. These field trips give students hands-on laboratory experiences, and the visual nature of microscopy makes it easy to get students excited about their visit. ****TECHNICAL ABSTRACT**** The glass transitions of polymer glasses and molecular glasses are usually studied in the context of macroscopically large systems. However, confining samples so that one or more dimensions are microscopic typically changes the behavior of the sample, for example changing the temperature at which the sample becomes a glass. This individual investigator award supports a project to study a colloidal suspension confined in thin sample chambers as a model system for glass transitions in confined geometries. Colloidal suspensions are composed of microscopic-sized solid particles in a liquid; this system behaves analogous to a glass if the particle concentration is sufficiently high. Experiments will use confocal microscopy to directly observe the motion of colloidal particles and how this motion changes in confinement. Understanding the physical effects of confinement on materials is increasingly important today as more and more technology is built at the scale of nanometers. This project provides training and education for both undergraduate and graduate students. The laboratory will conduct at least one field trip each year for groups of high school school students. These field trips give students hands-on laboratory experiences, and the visual nature of the research makes it easy to get students excited about their visit.