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Modeling Statics and Dynamics Behavior of Ionic Block Copolymer via Coarse-Grained Molecular Dynamics Simulation

Ma, Mengze
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613748189579107

Abstract Details

2021, PhD, University of Cincinnati, Engineering and Applied Science: Aerospace Engineering.
Ionic polymer has attracted significant research interests due to its recent advances in energy storage devices especially serves as solid electrolyte and robust membrane for fuel cell. Current challenges for such kind of application are the ion transport speed and mechanical property. In general, there is a lack of understanding of decoupling of the ion transport and the rigidity of polymer chain as well as understand the electrostatic strength affecting the polymer’s mechanical behavior. In this dissertation, coarse-grained molecular dynamics (CGMD) simulation is adopted to address these challenges. In the study of ion transport, the counterions have significant influence on the coupled dynamics of the charges on the chains and counterions. The coupled dynamics between the charged monomers and the counterions becomes stronger with increasing counterion size. The static dielectric permittivity of the polymer also has a significant effect on the coupling as well as the glass transition temperature. The predicted glass transition temperature decreases with an increase in the dielectric permittivity of the polymer, which also leads to an increase in the diffusivity of the counterions at a given temperature. Backbone rigidity is proved to lead a decrease in coupling as well as an increase in glass transition temperature which are further confirmed by experimental works. Furthermore, semi-flexible chains are predicted to have faster counterion dynamics comparing to the flexible chains with same segmental relaxation time. In the terms of mechanical property, the effect of charge ratio and loading direction on the stress-strain behavior are studied. the electrostatic interactions between charges paly important roles, as evidenced by increased yield strength and Young’s modulus with charge ratio. Introduced charge pairs leads to an increased randomness in segmental orientation in block copolymers. Furthermore, the tension-recovery studies reveal property of mechanical integrity which is important for designing the polymer electrolyte. Dynamic hysteresis loss and permanent displacement are strongly influenced by the fraction of charged block as well as the charge ratio. Meanwhile, the charged copolymers are subject to more changes in bond orientation during tension and preserve more changes at recovery. Effects of an applied electric field on ion transport, morphological changes and stress build-up are studied in detail as well. Three stages of BCP evolution under electric field are found and characterized. These stages are mainly characterized by ion dissociation as well as the stress distribution, where the final stage is defined as the steady state. This part of work paves a way towards establishing a modeling scheme that couple morphology to ion transport in the presence of applied electric field. The research presented in this dissertation addressed the decoupling of the chain rigidity and deformation mechanism of single-ion homopolymer and di-block copolymer via a MD simulation approach.
Yao Fu, Ph.D. (Committee Chair)
Woo Kyun Kim, Ph.D. (Committee Member)
Gui-Rong Liu, Ph.D. (Committee Member)
150 p.
Materials Science
ionic polymer; molecular dynamics

Recommended Citations

Citations

  • Ma, M. (2021). Modeling Statics and Dynamics Behavior of Ionic Block Copolymer via Coarse-Grained Molecular Dynamics Simulation [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613748189579107

    APA Style (7th edition)

  • Ma, Mengze. Modeling Statics and Dynamics Behavior of Ionic Block Copolymer via Coarse-Grained Molecular Dynamics Simulation. 2021. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613748189579107.

    MLA Style (8th edition)

  • Ma, Mengze. "Modeling Statics and Dynamics Behavior of Ionic Block Copolymer via Coarse-Grained Molecular Dynamics Simulation." Doctoral dissertation, University of Cincinnati, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613748189579107

    Chicago Manual of Style (17th edition)

ucin1613748189579107
120
© 2020, some rights reserved.Creative Commons License Modeling Statics and Dynamics Behavior of Ionic Block Copolymer via Coarse-Grained Molecular Dynamics Simulation by Mengze Ma is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.