282721 Extracting Fundamental Materials Properties From Rheological Measurements

Wednesday, October 31, 2012: 9:30 AM
409 (Convention Center )
Folarin Latinwo and Charles M. Schroeder, Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL

Extracting Fundamental Materials properties from Rheological Measurements

Folarin Latinwo1 and Charles M. Schroeder1

1Department of Chemical & Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801

A long standing problem in complex fluids has been the determination of fundamental materials properties (e.g. elasticity) from dynamic far-from-equilibrium measurements (e.g. transient stresses). We recently developed a framework to extract information about polymer elasticity from trajectories of conformational changes of single molecules induced by fluid flow [1]. In our approach, we applied tools from non-equilibrium statistical mechanics namely the Jarzynski relation [2] to complex fluids via Brownian dynamics (BD) simulations of bead-spring models of polymer molecules. The relation allows for the calculation of free energy changes from work distributions of arbitrarily far-from-equilibrium processes and has been applied as originally conceived only to single molecule studies. In our current work, we demonstrate the further application of this new tool to complex fluids by determination of free energy changes from transient bulk stresses. Using BD simulations of bead-spring models of dsDNA and polystyrene molecules in various flow types (shear and extensional) and standard expressions for the stress tensor (e.g. Kramers-Kirkwood), we make a connection between stresses, work distributions of bulk measurements and the Jarzynski relation. In doing this, we developed a formalism to extract new fundamental information such as free energies (which intrinsically defines a system) from previously existing measurements.

 

[1] Latinwo, F. and Schroeder, C. M. Physical Review Letters, submitted.

[2] Jarzynski, C. Phys. Rev. Lett. 78, 2690--2693 (1997).


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See more of this Session: Complex Fluids
See more of this Group/Topical: Engineering Sciences and Fundamentals