Donald E. Sullivan
I obtained my B.Sc. degree at McGill University in 1972, majoring in chemistry. I then went on to graduate studies at the Massachusetts Institute of Technology, Department of Chemistry, specializing in statistical mechanics of liquids, and graduated with a Ph.D. in 1976. Following that, I did a 16-month postdoc at the State University of New York at Stony Brook, Department of Mechanics, again researching several aspects of the statistical mechanics of liquids, especially interfacial phenomena. I then did a further 8-month postdoc at the National Research Council in Ottawa, continuing my previous research.
In September 1978, I joined the faculty of the Department of Physics at the University of Guelph, where I have been ever since. Since then, I have held short-term Visiting Professorships at Cornell University and McGill University. From 2002 to 2005, I served as Director of the Guelph-Waterloo Physics Institute, the joint graduate program in physics at the Universities of Guelph and Waterloo. Prior to that, as well as in the period following that until 2008, I also served as departmental graduate coordinator.
My research is funded by the Natural Sciences and Engineering Research Council (NSERC). I referee many research journals and grant applications, and in 2008 was deemed an "outstanding referee" by the American Physical Society.
My current research falls mainly into the field of theoretical “soft condensed matter physics”. Systems in this field include conventional liquids as well as liquid and solid phases of materials such as polymers, lipids, and other biomaterials like proteins. My primary focus is the study of “liquid crystal” (LC) phases of these materials. As the name implies, these types of phases (sometimes called mesophases) exhibit properties which are a blend of those of conventional liquids and solids. Presently, LC’s are most well known in connection with LC display devices. These phases come about because the molecules are elongated and can roughly be pictured as a collection of pencils, all pointing on average in the same direction. There are several different types of mesophases, but my recent focus has been on so-called “smectic” phases, which have an additional type of organization, namely a layered structure like a stack of papers. (A similar type of structure characterizes biological membranes.) In general, the directional (or orientational) structure of mesophases produces behavior, such as in the scattering of light waves, which is intermediate between those of conventional liquids and solids.
My work has focused on the nature of the interactions between molecules of these systems which can produce such LC phases, most recently in polymers. In particular, I have concentrated on the effects of so-called “excluded-volume” interactions, which basically result because the presence of a molecule excludes any other molecules from occupying the same space and are always present regardless of any other types of interactions. The statistical description of these systems is complicated due to the fact that polymeric molecules are flexible or “wiggly”, i.e., cannot be simply pictured as straight pencils, which leads to several mathematical complexities. Recently, I have studied two models, both in the framework of what is called “self-consistent field theory”. One is a discrete model, in which a polymeric molecule is constructed from a chain of hard-sphere beads. The other model is a continuum version of the first one, what’s called the “wormlike-chain” model, in which the polymers are pictured as flexible strings. The approaches to solving the theory for these models rely heavily on numerically-intensive computational techniques, facilitated in large part by SHARCNET. The two models yield complementary information on aspects such as dependence of phase boundaries, i.e., the relation between density and pressure, on properties such as the length-to-width ratio of the molecules and their degree of flexibility. Besides polymers, one other type of system to which these studies have been successfully applied is aqueous suspensions of certain viruses.