Unraveling the molecular motions of viscous fluids and fluids under nano-confinement with NMR measurements and MD simulations
Dr. Philip M. Singer and Dr. Dilip Asthagiri,
Department of Chemical and Biomolecular Engineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
NMR relaxation dispersion (NMRRD) is a powerful tool to explore the molecular motions of fluids non-destructively, and it finds use in applications as diverse as imaging the state of tissues in the human body to characterizing fluids in sedimentary rocks. The physical principles governing NMRRD are well established. However, the models to interpret NMRRD still rely on severe assumptions about molecular geometries and molecular motions. With the objective of understanding the molecular motions of complex fluid systems, over the last few years we initiated a program to synergistically use NMRRD measurements and atomistic molecular dynamics (MD) simulations of H-H dipole-dipole relaxation to understand and enhance the interpretation of NMRRD. In this webinar we will show examples of our synergistic approach on low-viscosity fluids such as water and alkanes, high-viscosity fluids such as polydisperse polymers and bitumen, and, low-viscosity fluids under nano-confinement such as heptane confined in kerogen or polymer matrices. Our results indicate that the NMRRD of these complex fluid systems is dominated by H-H dipole-dipole interactions instead of paramagnetism, and that the molecular motions of these complex fluid systems can be characterized by a set of molecular modes in the distribution of molecular correlation times.
Dr. Philip M. Singer’s main interests are NMR petrophysics of unconventional shale reservoirs, and interpretation NMR relaxation from molecular dynamics simulations. Currently he is a research scientist in the Hirasaki research group at Rice University. He is also chief scientist and owner of Singer Technologies LLC, a partnership focused on NMR petrophysics consulting. Previously he was a senior research scientist at Schlumberger-Doll Research and Schlumberger Dhahran Carbonate Research. He received an MPhys from the University of Oxford, a PhD in physics from the Massachusetts Institute of Technology in NMR condensed matter physics, and a Marie Curie Fellowship for post-doctoral studies at the University of Paris-Sud.
Dr. Dilip Asthagiri’s interests are in the statistical mechanics of liquids and soft-matter. He has contributed to developing the modern quasichemical theory of solutions, an approach that enabled the first all-atom calculation of the hydration thermodynamics of a realistic protein. He has also contributed to crafting simulations and analysis to understand NMR relaxation of bulk and confined fluids. Dr. Asthagiri is an Associate Research Professor at Rice University. His recent appointments include a stint as a Visiting Scientist at the University of Texas Medical Branch and as an assistant professor at Johns Hopkins University. Dr. Asthagiri received his doctorate from the University of Delaware and his Bachelor’s from the Indian Institute of Technology (Madras), all in Chemical Engineering.