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 Jacqueline
L. Goveas
Adjunct
Assistant Professor in Chemical Engineering
Research Interests:
Education:
- B.S. (1991) University of Texas at Austin
- Ph.D. (1996) Princeton University
My research focuses on the dynamics of complex fluids. Over the
past two decades, complex fluids (polymers, surfactants, colloids,
liquid crystals, etc.) have been the source of a host of
novel materials, whose equilibrium properties are now well-studied.
However, these same systems exhibit fascinating dynamical behavior,
much of which is yet to be explained. I am particularly interested
in the coupling between flow and the supramolecular structure that
exists in a complex fluid. This structure can generate interesting
flow behavior such as viscoelasticity and non-linear rheology. Conversely,
flow can affect structure, perturbing phase transitions, and sometimes
by inducing phases that only exist as static metastable phases,
or not at all. Since energy is constantly being fed into a system
under flow, we cannot use equilibrium statistical mechanics to solve
these problems, and must develop appropriate new methodologies.
Shear-Thickening: Some complex fluids exhibit an increasing
viscosity as a function of shear rate. Shear-thickening during industrial
processing generally ruins the application the complex fluid is
used for. The source of this behavior is fundamentally not understood,
but is thought to be due to the formation of shear-induced structures
in the liquid. In addition, these systems can become inhomogeneous
under a shear flow, segregating into regions of different shear
rates with sharp interfaces between them. I am formulating microscopic
models that describe shear-thickening in associating polymers and
"worm-like" (long, cylindrical) micellar solutions. An important
feature of these models is that they can produce the "shear-banding"
that is observed experimentally.
Polymer Melt Extrusion: Melt extrusion is a melt-forming
operation whereby a polymeric melt is forced from a larger barrel
through a much narrower capillary. Under normal operating conditions,
melt-flow instabilties can set in, distorting the extrudate and
rendering it unusable. A variety of dynamical phenomena arise in
conjunction with these instabilties, including stick-slip transitions
at the capillary wall and flow-induced crystallization. Here again,
my approach involves solving microscopic models for polymer melts
coupled to macroscopic equations of change for the system.
Emulsions under flow: Recent experiments (Mason and Bibette,
1996) have produced monodisperse emulsions by simply shearing viscoelastic
oil-in-water emulsions. Emulsions are ubiquitous in the food, cosmetics
and paint industries, where controlling drop size is crucial to
tailoring product properties. Inspired by this experiment, I am
using a combination of experiment (video microscopy) and theory
(mainly low Reynolds-number hydrodynamics) to study how drops deform
and break in highly viscoelastic, concentrated emulsions. Work on
drop deformation and break-up goes back to that of G.I. Taylor in
the 30's, but it has largely focused on dilute, Newtonian systems.
I would also like to extend these studies to polymeric emulsions.
Selected Publications
- "Identification of the Molecular Parameters that Govern Ordering
Kinetics in Block CopolymerMelt" Macromolecules 1998, to
be published, N.P. Balsara, B.A. Garetz, M.Y. Chang, H.J. Dai,
M.C. Newstein, J.L. Goveas, R. Krishnamoorti, S. Rai
- "Apparent Slip at a Polymer-Polymer Interface" Eur. Phys.
J. B 2, 79-92 (1998), J.L. Goveas, G.H. Fredrickson
- "Corrections to Strong-Stretching Theories" Macromolecules,
30, 5541 (1997), J.L. Goveas, S.T. Milner, W. B. Russel
- "Late Stages of the Pearling Instability in Lipid Bilayers",
Journal de Physique II,(France) 7, 1185 (1997),
J.L. Goveas, S.T. Milner, W. B. Russel
- "Dynamics of the Lamellar-Cylindrical Transition in Weakly Segregated
Diblock Copolymer Melts", Macromolecules, 30, 2605
(1997), J.L. Goveas, S.T. Milner.
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