Structure and Dynamics of Coarse-Grained Ionomer Melts in an External Electric Field

Ting, Christina; Stevens, Mark J.; Frischknecht, Amalie L.

doi:10.1021/ma501916z

Cited by 55 publications

(69 citation statements)

References 32 publications

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“…Ion transport mechanism. Efforts to reveal the ion transport mechanism in ion-containing polymers have been reported both experimentally and computationally [7][8][9][10][31][32][33][34] The consensus from previous studies on how the counterions move in a polymer melt (in the absence of any electric field) is that the counterions have either structural diffusion or vehicular transport. [31][32][33][34] In the former mechanism, the counterions are hopping between oppositely charged monomers, whereas in the latter, the ions diffuse along with their neighbors, that is, an aggregate of counterions and charged monomers moving together.…”

Section: Ionic Clustersmentioning

confidence: 99%

Control of Ionic Mobility via Charge Size Asymmetry in Random Ionomers

Nguyen

Cruz

2019

Nano Lett.

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Solid polymer electrolytes are considered a promising alternative to traditional liquid electrolytes in energy storage applications because of their good mechanical properties, and excellent thermal and chemical stability. A gap, however, still exists in understanding ion transport mechanisms and improving ion transport in solid polymer electrolytes. Therefore, it is crucial to bridge composition-structure and structure-property relationships. Here we demonstrate that size asymmetry, λ , represented by the ratio of counterion to charged monomer size, plays a key role in both the nanostructure and in the ionic dynamics. More specifically, when the nanostructure is modified by the external electric field such that the mobility cannot be described by linear response theory, two situations arise. The ionic mobility increases as λ decreases (small counterions) in the weak electrostatics (high dielectric constant) regime.Whereas in systems with strong electrostatic interactions, ionomers with higher size symmetry (λ ≈ 1) display higher ionic mobility. Moreover, ion transport is found to be dominated by the 1 arXiv:1907.03946v1 [cond-mat.mtrl-sci] 9 Jul 2019 hopping of the ions and not by moving ionic clusters (also known as "vehicular" charge transport). These results serve as a guide for designing ion-containing polymers for ion transport related applications. IntroductionIon-containing polymers are a class of materials which have generated great interest over the past few decades, due to their various applications such as solid polymer electrolytes for ion batteries and fuel cells, organic field-effect transistors, and water purification membranes. 1-5 Ion transport properties in such materials are of interest in many of these applications and has been extensively investigated through experimental, theoretical, and computational approaches. 6-12 Evidently, the structural features of the assembled nanostructures, particularly the morphology of the ionic aggregates formed in ion-containing polymers, strongly influence the dynamics of coand counterions with and without an external electric field. 13,14 Therefore, understanding both the structure-property relationship and composition-structure relationship contributes to better design of ion-containing polymeric materials tailored for different applications.Charge fraction has been shown to be a very effective tuning parameter to achieve different morphologies in ion-containing polymers. [15][16][17][18][19][20] For instance, Sing et al. demonstrated that the Coulombic interaction between charged monomers and counterions lead to nontrivial effects in the phase behavior of polymer blends and block copolymers. 15,16 Shim and coworkers discovered a superlattice morphology by varying the charge content of charged block copolymers. 18 Our previous work demonstrated that ionic correlations in random ionomers lead to nanostructures with composition polydispersity, which are desired for ion battery and fuel cell applications. 21 Random ionomers, whose fraction and sequence of ch...

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Section: Ionic Clustersmentioning

confidence: 99%

Control of Ionic Mobility via Charge Size Asymmetry in Random Ionomers

Nguyen

Cruz

2019

Nano Lett.

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“…The influences of the counterions on the polyelectrolyte dynamics are certainly nontrivial, at the length scales of the monomers and of the sub-chains. 40,41 Webb and coworkers showed that the dynamics of a single negatively charged polyelectrolyte is substantially suppressed across multiple length scales for different concentrations of lithium cations compared to that of neat polymers. 41 Here we also characterize the dynamics of the confined polyelectrolyte at different length scales through the relaxation time of its Rouse modes.…”

Section: Relaxation Time Of the Rouse Modes Of The Polyelectrolytementioning

confidence: 99%

Manipulation of Confined Polyelectrolyte Conformations through Dielectric Mismatch

Nguyen

Cruz

2019

ACS Nano

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We demonstrate that a highly charged polyelectrolyte confined in a spherical cavity undergoes reversible transformations between amorphous conformations to a four-fold symmetry morphology as a function of dielectric mismatch between the media inside and outside the cavity. Surface polarization due to dielectric mismatch exhibits an extra "confinement" effect, which are most pronounced within a certain range of the cavity radius and the electrostatic strength between the monomers and counterions and multivalent counterions. For cavities with a charged surface, surface polarization leads to an increased amount of counterions adsorbed in the outer side, further compressing the confined polyelectrolyte into a four-fold symmetry morphology. The equilibrium conformation of the chain is dependent upon several key factors including the relative permittivities of the media inside and outside the cavity, multivalent counterion concentration, cavity radius relative to the chain length, and interface charge density. Our findings offer insights into the effects of dielectric mismatch in packaging and delivery of polyelectrolytes across media with different relative permittivities. Moreover, the reversible transformation of the polyelectrolyte conformations in response to environmental permittivity allows for potential applications in biosensing and medical monitoring.

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“…Sethuraman et al has observed that five different ion transport mechanisms in lamellar BCPs and homopolymers (HPs), and that the mean square displacement of BCPs decreases with increasing charge ratio [25]. Ting et al found that the ion transport of ionomer melt displays a different regime influenced by the strength of electric field and the ionic aggregate morphology [26]. However, there exist relatively few studies that attempt to understand the mechanical properties of the charged BCPs.…”

Section: Introductionmentioning

confidence: 99%

Structural and Mechanical Properties of Ionic Di-block Copolymers via a Molecular Dynamics Approach

2019

Polymers

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Polymerized ionic copolymers have recently evolved as a new class of materials to overcome the limited range of mechanical properties of ionic homopolymers. In this paper, we investigate the structural and mechanical properties of charged ionic homopolymers and di-block copolymers, while using coarse-grained molecular dynamics simulation. Tensile and compressive deformation are applied to the homopolymers and copolymers in the glassy state. The effect of charge ratio and loading direction on the stress-strain behavior are studied. It is found that the electrostatic interactions among charged pairs play major roles, as evidenced by increased Young’s modulus and yield strength with charge ratio. Increased charge ratio lead to enhanced stress contribution from both bonding and pairwise (Van der Waals + coulombic) interaction. The increase in the gyration of the radius is observed with increasing charge ratio in homopolymers, yet a reversed tendency is observed in copolymers. Introduced charge pairs leads to an increased randomness in the segmental orientation in copolymers.

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Structure and Dynamics of Coarse-Grained Ionomer Melts in an External Electric Field

Cited by 55 publications

References 32 publications

Control of Ionic Mobility via Charge Size Asymmetry in Random Ionomers

Control of Ionic Mobility via Charge Size Asymmetry in Random Ionomers

Manipulation of Confined Polyelectrolyte Conformations through Dielectric Mismatch

Structural and Mechanical Properties of Ionic Di-block Copolymers via a Molecular Dynamics Approach

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