Home > Lisa Hall: Phase Behavior and Dynamics of Model Tapered Diblock Polymers

Lisa Hall: Phase Behavior and Dynamics of Model Tapered Diblock Polymers

Start:

10/10/2017 at 12:30PM

End:

10/10/2017 at 1:30PM

Location:

138 DeBartolo Hall

Host:

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Jonathan Whitmer

Jonathan Whitmer

VIEW FULL PROFILE Email: jwhitme1@nd.edu
Phone: 574-631-1417
Office: 122 Cushing

Affiliations

College of Engineering Assistant Professor
Equilibrium and Nonequilibrium Polyelectrolytes: Much in our world exists out of equilibrium. Weather patterns develop and disperse; cells grow and multiply; combustion engines turn molecular bonds into usable energy. Manufacturing processes utilize shear, compression, extrusion and flow to ...
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Diblock copolymers, containing two blocks of chemically different monomers A and B connected into the same chain, are known to microphase separate into various structures, such as spheres, cylinders, bicontinuous networks, and lamellae, depending on the fraction of A and B and how unfavorable the A-B interactions are. Increased understanding and control over these nanoscale structures and the dynamics of small molecules or ions within them would advance development of mechanically robust but conductive materials for battery electrolytes, among other applications.  We model diblock polymers with a gradient region inserted between the pure A and B blocks such that the composition smoothly transitions from A to B (or B to A in the case of inverse tapers).

 

We predict a widening of the bicontinuous double gyroid region of the phase diagram for moderate length normal tapers versus typical diblocks, suggesting taper length can be used as a control parameter to obtain such network phases even at high molecular weight, as may be desirable in transport applications. We use both coarse-grained molecular dynamics (MD) simulations and fluids (classical) density functional theory (fDFT) in concert to study the same model system from two compatible points of view. Free energies of various microphases are readily accessible from fDFT, which allows us to efficiently determine the equilibrium nanostructure over a large parameter space. Recent advances in the theoretial approach allow us to consider ion-containing systems as well. Meanwhile, MD allows us to visualize specific polymer conformations in 3D over time (e.g. MD simulations show how the chains fold back and forth across the interface in inverse tapered polymer systems) and to calculate how tapering and salt content affects dynamic properties such as diffusion.

Seminar Speaker:

Lisa Hall

Lisa Hall

The Ohio State University

Lisa Hall is the H. C. “Slip” Slider Assistant Professor at the Ohio State University. She joined OSU in 2012, having completed her Ph.D. with Prof. Ken Schweizer at the University of Illinois and a subsequent postdoctoral appointment with Amalie Frischknecht and Mark Stevens at Sandia National Laboratories. Her research group uses statistical mechanical theory and molecular dynamics simulations to understand the structure and dynamics of nanostructured polymers. Systems of interest include ion containing block copolymers, ionomers, and nanocomposites. She received a CAREER award from the National Science Foundation in 2015, centered on efficiently modeling ion conduction in block copolymer electrolytes.

https://hallgroup.engineering.osu.edu/