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Title: Odd–Even Structural Sensitivity on Dynamics in Network-Forming Ionic Liquids

Abstract

As a compelling case of sensitive structure–property relationship, an odd–even effect refers to the alternating trend of physical or chemical properties on odd/even number of repeating structural units. In crystalline or semicrystalline materials, such odd–even effects emerge as manifestations of differences in the periodic packing patterns of molecules. Therefore, due to the lack of long-range order, such an odd–even phenomenon is not expected for dynamic properties in amorphous state. Herein, we report the discovery of a remarkable odd–even effect of dynamical properties in the liquid phase. In a class of glass-forming diammonium citrate ionic liquids, using incoherent quasi-elastic neutron scattering measurements, we measured the dynamical properties including diffusion coefficient and rotational relaxation time. These directly measured molecular dynamics showed pronounced alternating trends with increased number of methylene (-CH2-) groups in the backbone. Meanwhile, the structure factor S(Q) showed no long-range periodic packing of molecules, while the pair distribution function G(r) revealed subtle differences in the local molecular morphology. The observed dynamical odd–even phenomenon in liquids showed that profound dynamical changes originate from subtle local structural differences.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1377908
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemistry of Materials; Journal Volume: 28; Journal Issue: 9
Country of Publication:
United States
Language:
ENGLISH
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE

Citation Formats

Yang, Ke, Cai, Zhikun, Tyagi, Madhusudan, Feygenson, Mikhail, Neuefeind, Joerg C., Moore, Jeffrey S., and Zhang, Yang. Odd–Even Structural Sensitivity on Dynamics in Network-Forming Ionic Liquids. United States: N. p., 2016. Web. doi:10.1021/acs.chemmater.6b01429.
Yang, Ke, Cai, Zhikun, Tyagi, Madhusudan, Feygenson, Mikhail, Neuefeind, Joerg C., Moore, Jeffrey S., & Zhang, Yang. Odd–Even Structural Sensitivity on Dynamics in Network-Forming Ionic Liquids. United States. doi:10.1021/acs.chemmater.6b01429.
Yang, Ke, Cai, Zhikun, Tyagi, Madhusudan, Feygenson, Mikhail, Neuefeind, Joerg C., Moore, Jeffrey S., and Zhang, Yang. Tue . "Odd–Even Structural Sensitivity on Dynamics in Network-Forming Ionic Liquids". United States. doi:10.1021/acs.chemmater.6b01429.
@article{osti_1377908,
title = {Odd–Even Structural Sensitivity on Dynamics in Network-Forming Ionic Liquids},
author = {Yang, Ke and Cai, Zhikun and Tyagi, Madhusudan and Feygenson, Mikhail and Neuefeind, Joerg C. and Moore, Jeffrey S. and Zhang, Yang},
abstractNote = {As a compelling case of sensitive structure–property relationship, an odd–even effect refers to the alternating trend of physical or chemical properties on odd/even number of repeating structural units. In crystalline or semicrystalline materials, such odd–even effects emerge as manifestations of differences in the periodic packing patterns of molecules. Therefore, due to the lack of long-range order, such an odd–even phenomenon is not expected for dynamic properties in amorphous state. Herein, we report the discovery of a remarkable odd–even effect of dynamical properties in the liquid phase. In a class of glass-forming diammonium citrate ionic liquids, using incoherent quasi-elastic neutron scattering measurements, we measured the dynamical properties including diffusion coefficient and rotational relaxation time. These directly measured molecular dynamics showed pronounced alternating trends with increased number of methylene (-CH2-) groups in the backbone. Meanwhile, the structure factor S(Q) showed no long-range periodic packing of molecules, while the pair distribution function G(r) revealed subtle differences in the local molecular morphology. The observed dynamical odd–even phenomenon in liquids showed that profound dynamical changes originate from subtle local structural differences.},
doi = {10.1021/acs.chemmater.6b01429},
journal = {Chemistry of Materials},
number = 9,
volume = 28,
place = {United States},
year = {Tue May 10 00:00:00 EDT 2016},
month = {Tue May 10 00:00:00 EDT 2016}
}