Role of Solvation on Diffusion of Ions in Diblock Copolymers: Understanding the Molecular Weight Effect through Modeling

Seo, Youngmi; Shen, Kuan-Hsuan; Brown, Jonathan R.; Hall, Lisa M.

doi:10.1021/jacs.9b07227

Title: Role of Solvation on Diffusion of Ions in Diblock Copolymers: Understanding the Molecular Weight Effect through Modeling

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Abstract

Salt-doped diblock copolymers with microphase-separated domains of both an ion conductive and a mechanically strong polymer have been extensively studied due to their potential in transport applications. Several unusual or counterintuitive trends regarding their transport properties have been observed experimentally, such as increasing ion conduction as a function of molecular weight. A vital feature of these systems is the strong solvation of ions in the conducting microphase due to its higher dielectric constant. Herein, we perform molecular dynamics simulations using a coarse-grained model that includes a 1/r⁴ potential form to generically represent ion solvation, allowing us to reproduce experimentally observed trends and explore their molecular underpinnings. We find that increasing ion concentration can increase or decrease ion diffusion, depending on solvation strength. We further show that the trend of increasing diffusion with molecular weight becomes more dramatic as ions are solvated in one polymer block more strongly or as the ion-ion interactions get stronger. In contrast to expectations, the interfacial width or the overlap of ions with the nonconductive polymer block do not adequately explain this phenomenon; instead, local ion agglomeration best explains reduced diffusion. Interfacial sharpening, controlled by the Flory chi parameter and molecular weight, tends to allow ionsmore »« less

Authors:

Seo, Youngmi ^[1]; Shen, Kuan-Hsuan ^[1];

^[1];

^[1]

The Ohio State Univ., Columbus, OH (United States)

Publication Date:: Fri Nov 01 00:00:00 EDT 2019

Research Org.:: The Ohio State Univ., Columbus, OH (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF)

OSTI Identifier:: 1631420

Grant/Contract Number:: SC0014209

Resource Type:: Accepted Manuscript

Journal Name:: Journal of the American Chemical Society

Additional Journal Information:: Journal Volume: 141; Journal Issue: 46; Journal ID: ISSN 0002-7863

Publisher:: American Chemical Society (ACS)

Country of Publication:: United States

Language:: English

Subject:: 36 MATERIALS SCIENCE

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                    Seo, Youngmi, Shen, Kuan-Hsuan, Brown, Jonathan R., and Hall, Lisa M. Role of Solvation on Diffusion of Ions in Diblock Copolymers: Understanding the Molecular Weight Effect through Modeling.  United States: N. p., 2019. 
Web.  doi:10.1021/jacs.9b07227.

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                    Seo, Youngmi, Shen, Kuan-Hsuan, Brown, Jonathan R., & Hall, Lisa M. Role of Solvation on Diffusion of Ions in Diblock Copolymers: Understanding the Molecular Weight Effect through Modeling.  United States.  https://doi.org/10.1021/jacs.9b07227

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                    Seo, Youngmi, Shen, Kuan-Hsuan, Brown, Jonathan R., and Hall, Lisa M. Fri .  
"Role of Solvation on Diffusion of Ions in Diblock Copolymers: Understanding the Molecular Weight Effect through Modeling".  United States.  https://doi.org/10.1021/jacs.9b07227.  https://www.osti.gov/servlets/purl/1631420.

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@article{osti_1631420,

  title        = {Role of Solvation on Diffusion of Ions in Diblock Copolymers: Understanding the Molecular Weight Effect through Modeling},

  author       = {Seo, Youngmi and Shen, Kuan-Hsuan and Brown, Jonathan R. and Hall, Lisa M.},

  abstractNote = {Salt-doped diblock copolymers with microphase-separated domains of both an ion conductive and a mechanically strong polymer have been extensively studied due to their potential in transport applications. Several unusual or counterintuitive trends regarding their transport properties have been observed experimentally, such as increasing ion conduction as a function of molecular weight. A vital feature of these systems is the strong solvation of ions in the conducting microphase due to its higher dielectric constant. Herein, we perform molecular dynamics simulations using a coarse-grained model that includes a 1/r4 potential form to generically represent ion solvation, allowing us to reproduce experimentally observed trends and explore their molecular underpinnings. We find that increasing ion concentration can increase or decrease ion diffusion, depending on solvation strength. We further show that the trend of increasing diffusion with molecular weight becomes more dramatic as ions are solvated in one polymer block more strongly or as the ion-ion interactions get stronger. In contrast to expectations, the interfacial width or the overlap of ions with the nonconductive polymer block do not adequately explain this phenomenon; instead, local ion agglomeration best explains reduced diffusion. Interfacial sharpening, controlled by the Flory chi parameter and molecular weight, tends to allow ions to spread more uniformly, and this increases their diffusion.},

  doi          = {10.1021/jacs.9b07227},

  journal      = {Journal of the American Chemical Society},

  number       = 46,

  volume       = 141,

  place        = {United States},

  year         = {Fri Nov 01 00:00:00 EDT 2019},

  month        = {Fri Nov 01 00:00:00 EDT 2019}

}

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