Grant: Discovery Grants Program - Individual

Rheology is the study of the flow and deformation of matter. Not of simple matter, like water or air, but complex matter, like sticky, gooey, elastic liquids. These fluids are complex because their molecules are long and chainlike. My rheological research is all about connecting the motions and alignments of these long chain molecules with liquid elasticity. We will uncover these connections by carefully jiggling the polymer molecules in the latest expensive, sophisticated, computerized instruments called rheometers. Over the period of my Discovery Grant, and for years beyond, my team will explore the relation between the molecular structure of elastic liquids, and their rheology in jiggling experiments called large-amplitude oscillatory shear (LAOS).*We care about oscillatory shear because it is the most popular viscoelastic property measurement, and when done at large amplitude, this test can uncover a rich diversity of interesting detail about the nonlinear viscous and elastic parts of a complex liquid response. Since my doctoral thesis on this subject [McGill, Chemical Engineering (1987)], my group has been a leading laboratory on the characterization of polymeric liquids in LAOS. *To deepen our understanding of these responses, in terms of the liquid microstructure, my group is now turning its attention to the use of kinetic molecular theory to explore the connections between molecular structure and the stress response in LAOS [JCP, 140, 074904 (2014)]. Over the next five years, we aim to calculate the stress response of the polymeric liquid in terms of the length of the model molecule in oscillatory shear flows, and to compare these predictions with our experimental measurements. Specifically, we aim to vary the molecular structure in the laboratory, and to explore its effect on the rheological response. Special problems arise when extending the kinetic molecular theory for polydisperse systems, since the relaxation spectrum departs from the Maxwell model. Over the next five years, my group will tackle these special theoretical problems.*My new Queen's laboratory will soon be equipped with the latest breakthrough instrument for measuring rheological response in LAOS: cone-plate flow with plate partitioning. Having spent last summer collaborating in Germany to perfect this technique, I design this proposal to exploit the resources of my new Canada Research Chair in Rheology, and especially the new equipment on order from the corresponding CFI monies. We seek Discovery Grant support for postdoctoral and doctoral students to evaluate the latest advances in structural theory with careful measurements on polymeric liquids of known molecular structure.*