Spatial-Temporal Characteristics of Confined Polymer Motion

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Chemical and Dynamical Processes in Solution; Polymers, Glasses, and Soft Matter

Spatial-Temporal Characteristics of Confined Polymer Motion Determine Proton Conduction of PolyoxometalatePoly(ethylene glycol) Hybrid Nanocomposites Huarui Wu, Lengwan Li, Masaki Tsuboi, Yongqiang Cheng, Weiyu Wang, Eugene Mamontov, Sayaka Uchida, Zhe Wang, and Panchao Yin J. Phys. Chem. Lett., Just Accepted Manuscript • DOI: 10.1021/acs.jpclett.8b02113 • Publication Date (Web): 14 Aug 2018 Downloaded from http://pubs.acs.org on August 17, 2018

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The Journal of Physical Chemistry Letters

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The view of crystalline structures of the POM-PEG hybrid material along c axis (panel (a)) and a axis (panel (b)). Color codes: blue polyhedron, MoO6; purple polyhedron, SiO4; yellow sphere, Cs+; red circle, 6 Å channel; purple circle, 8 Å channel. 83x47mm (300 x 300 DPI)


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INS spectrum of the PEG confined in the framework defined by POMs (solid line) and that of a pure PEG (dashed line). Panels (a) and (b) display the intensities in the energy range of 5 to 80 meV and of 95 to 125 meV, respectively. The intensities of the confined PEG are shifted up for clarity. 60x84mm (300 x 300 DPI)



Conformation of the PEG inside the 1D nano-channel defined by the framework of POMs. In panel (a), the PEG chain is seen to stay as a distorted helix. Panel (b) illustrates the meanings of fitting parameters. The cylinder with a length of L and a radius of R denotes the space that a C atom can explore. D is the diffusivity of a C atom, and τ_R is the characteristic time of the two-side jump of an H atom in a methylene group. The double-headed arrow denotes the direction of the 1D nano-channel. 83x82mm (300 x 300 DPI)


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QENS spectra of the POM-PEG hybrid material at T=413 K and at three wave vector transfers Q = 0.5, 0.9 and 1.3 Å-1. The symbols denote the measured neutron intensities as a function of the energy transfer ω. The solid lines are the fitted curves. The fitting results are presented in both logarithmic scale (panel (a)) and linear scale (panel (b)) to provide an examination on the overall fitting quality. 114x51mm (300 x 300 DPI)



Proton conductivity σ (blue) and self-diffusion coefficient D (red) as a function of 1000/T. The symbols are experimental results, the solid lines denote the fitting results with Arrhenius law. 78x53mm (300 x 300 DPI)


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Spatial-Temporal Confined Polymer Proton Conduction Poly(ethylene Nanocomposites

Characteristics of Motion Determine of Polyoxometalateglycol) Hybrid

Huarui Wu‡, Lengwan Li†, Masaki Tsuboi⁋, Yongqiang Cheng§, Weiyu Wang†, Eugene Mamontov§, Sayaka Uchida⁋, Zhe Wang*,‡, and Panchao Yin*,† †

South China Advanced Institute for Soft Matter Science and Technology & State Key Laboratory of

Luminescent Materials and Devices, South China University of Technology, Guangzhou, China 510640 ‡

Department of Engineering Physics, Tsinghua University, Beijing, China 100084

⁋

Department of Basic Sciences, School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba,

Meguro-ku, Tokyo, Japan 153-8902 §

Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA 37831

*To whom correspondence should be addressed. E-mail: [email protected] (Z.W.); [email protected] (P.Y.)



Abstract Highly efficient proton conductors, polyoxometalate-poly(ethylene glycol) (POM-PEG) hybrid nanocomposites, have been synthesized by encapsulating single PEG chain inside the 1D nano-channel defined by the frameworks of POMs. By employing two types of neutron scattering techniques complemented by thermal analysis, we prove that in a nano-channel a single PEG chain stays as a distorted helix. More importantly, we reveal that the PEG segments perform a localized longitudinal random walk, and quantitatively show the strong correlation between the local motion of PEG and the macroscopic proton conduction of the material. Based on these spatial-temporal characteristics, a microscopic picture for the proton conduction process of POM-PEG hybrid materials is proposed.

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As the key elements in fuel cell devices, proton conductive materials are under intense research to meet urgent need for improving their conductivity and stability performances.1-3 The target proton conductors will be superionic materials with appropriate mechanical properties that can be operated at medium high temperature and low environment humidity.1-4 As a group of highly charged metal oxide clusters at nanoscale, polyoxometalates (POMs) possess appreciable stability against high temperature and promising proton conductivity at ambient environment.4-6 Thanks to the recent development in POM chemistry, these POMs can hybridize with polymers to form nanocomposites, which could significantly enhance POMs’ proton conductivity as well as mechanical properties.7-9 Specifically, we have previously prepared the POM-poly(ethylene glycol) (PEG) hybrid nanocomposites with PEG molecules encapsulated inside the nano-channels defined by POMs.4,10 The obtained anhydrous hybrid materials showed comparatively high proton conductivity at high temperature (up to 443 K) in low humidity environment (

Spatial-Temporal Characteristics of Confined Polymer Motion

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