Research Associate
Robert A. Riggleman
- B.S., University of South Carolina, 2002
- Ph.D., Chemical Engineering, University of Wisconsin-Madison, 2007
Research
My research is focused on providing a fundamental understanding of how the properties of glassy polymers change when they are confined to freestanding, nanoscale thin films. Many experiments have shown that there is a distribution of glass transition temperatures in thin films, and near free surfaces the dynamics are enhanced and the glass transition temperature decreases. Recently we have shown that the addition of antiplasticizer additives can homogenize the properties of the film and eliminate the effects of the free surface on the glass transition temperature. Currently, we are interested in how confinement affects the aging properties of glassy polymers and antiplasticized polymers. Because glassy materials are non-equilibrium systems, their properties are known to be a function of time; for longer "aging times", the glassy system approaches equilibrium as evidenced by a slow increase in the density and a decrease in the structural relaxation times. We therefore want to understand how the addition of antiplasticizer additives to glassy polymers affects their aging properties in bulk material and in freestanding thin films. Since aging is a phenomenon that occurs over many decades in time, it is necessary to develop new simulations techniques capable of exploring the dynamics over longer time scales than molecular dynamics.
Publications
- Robert A. Riggleman, Kenji Yoshimoto, Jack F. Douglas, and
Juan J. de Pablo.
"Influence of Confinement on the Fragility of Antiplasticized and Pure Polymer Films".
Physical Review Letters, 97(4):045502, July 27, 2006. [doi:10.1103/PhysRevLett.97.045502] [APS/PRL] - Robert A. Riggleman, Jack F. Douglas, and Juan J. de Pablo.
"Tuning Polymer Melt Fragility with Antiplasticizer Additives".
Journal of Chemical Physics 126(23):234903, June 19, 2007. [doi:10.1063/1.2742382] [AIP/JCP] - Robert A. Riggleman, Jack F. Douglas, and Juan J. de Pablo.
"Characterization of the potential energy landscape of an antiplasticized polymer".
Physical Review E 76(1):011504, July 6, 2007. [doi:10.1103/PhysRevE.76.011504] [APS/PRE] - Robert A. Riggleman, Hau-Nan Lee, Mark D. Ediger,
and Juan J. de Pablo.
"Free Volume and Finite-Size Effects in a Polymer Glass Under Stress".
Physical Review Letters, 99(21):215501, November 20, 2007. [doi:10.1103/PhysRevLett.99.215501] [APS/PRL]
Contact
Dr. Robert A. Riggleman
Department of Chemical and Biological Engineering
University of Wisconsin-Madison
3111 Engineering Hall
1415 Engineering Drive
Madison, WI 53706-1691
U.S.A.
email: rariggleman@wisc.edu
tel: +1 608 265-4926
fax: +1 608 262-5434
