Structural relaxation, viscosity, and network connectivity in a hydrogen bonding liquid

Stefania Perticaroli, Barmak Mostofian, Georg Ehlers, Joerg C. Neuefeind, Souleymane O. Diallo, Christopher B. Stanley, Luke Daemen, Takeshi Egami, John Katsaras, Xiaolin Cheng, Jonathan D. Nickels

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

In liquids, the ability of neighboring molecules to rearrange and jostle past each other is directly related to viscosity, the property which describes the propensity to flow. The presence of hydrogen bonds (H-bonds) complicates the molecular scale picture of viscosity. H-Bonds are attractive, directional interactions between molecules which, in some cases, result in transient network structures. In this work, we use experimental and computational methods to demonstrate that the timescale of H-bond network reorganization is the dominant dynamical timescale associated with viscosity for the case of the model H-bonding liquid n-methylacetamide (NMA). This molecule is a peptide analog which forms a transient linear H-bond network. Individual H-bond lifetimes and dynamical fluctuations were observed on the timescale of 1.5 ps, while collective motions and the longest lived population of H-bond partner lifetimes were observed on the order of 20 ps, in agreement with the Maxwell relaxation time. This identifies a mechanism which may aid in understanding the emergence of various complex phenomena arising from transient molecular structures, with implications ranging from the internal dynamics of proteins, to the glass transition, to better understanding the origins of the unique properties of H-bonding liquids.

Original languageEnglish
Pages (from-to)25859-25869
Number of pages11
JournalPhysical Chemistry Chemical Physics
Volume19
Issue number38
DOIs
StatePublished - 2017

Funding

We would like to acknowledge Prof. P. Pincus for helpful discussions and D. A. A. Myles for helpful discussions and supporting this work; R. Moody and R. Goyette for technical assistance. Research at Oak Ridge National Laboratory’s Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, DOE. Oak Ridge National Laboratory facilities are sponsored by UT-Battelle, LLC, for the U.S. Department of Energy under Contract no. DEAC0500OR22725. T. E. was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. This research was supported by an ASCR Leadership Computing Challenge (ALCC) award, and used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract no. DE-AC05-00OR22725.

FundersFunder number
Oak
Scientific User Facilities Division
UT-Battelle
U.S. Department of Energy
Office of Science
Basic Energy Sciences
Advanced Scientific Computing Research
Oak Ridge National Laboratory

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