Microphase Separation of Ionic Liquid-Containing Diblock Copolymers: Effects of Dielectric Inhomogeneity and Asymmetry in the Molecular Volumes and Interactions between the Cation and Anion

Nakamura, Issei

doi:10.1021/acs.macromol.0c00318

Cited by 10 publications

(13 citation statements)

References 57 publications

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“…They therefore suggested that the dielectric mismatch is the main reason for the drastic change in the phase diagram. In summary, factors including ion solvation energy, − ,− ,− ion translational entropy, ,,, ion correlation, − transient binding, ,, and asymmetry in the molecular volumes between cations and anions have been shown theoretically to impact the thermodynamics of ion-containing polymer systems. Although there is no agreement on which specific factor(s) leads to the change in the phase behavior of such ion-containing blends and copolymers, a well-accepted result is a quite asymmetric phase diagram with decreased compatibility when the charged (or salt-doped) component is in the minority.…”

Section: Resultsmentioning

confidence: 99%

Formation of a C15 Laves Phase with a Giant Unit Cell in Salt-Doped A/B/AB Ternary Polymer Blends

et al. 2020

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Salt-doped A/B/AB ternary polymer blends, wherein an AB copolymer acts as a surfactant to stabilize otherwise incompatible A and B homopolymers, display a wide range of nanostructured morphologies with significant tunability. Among these structures, a bicontinuous microemulsion (BμE) has been a notable target. Here, we report the surprising appearance of a robust C15 Laves phase, at compositions near where the BμE has recently been reported, in lithium bis(trifluoromethane) sulfonimide (LiTFSI)-doped low-molar-mass poly(ethylene oxide) (PEO)/polystyrene (PS)/symmetric PS-b-PEO block copolymer blends. The materials were analyzed by a combination of small-angle X-ray scattering (SAXS), 1H NMR spectroscopy, and impedance spectroscopy. The C15 phase emerges at a high total homopolymer volume fraction ϕH = 0.8 with a salt composition r = 0.06 (Li+/[EO]) and persists as a coexisting phase across a large area of the isothermal phase diagram with high PS homopolymer compositions. Notably, the structure exhibits a huge unit cell size, a = 121 nm, with an unusually high micelle core volume fraction (f core = 0.41) and an unusually low fraction of amphiphile (20%). This unit cell dimension is at least 50% larger than any previously reported C15 phase in soft matter, despite the low molar masses used, unlocking the possibility of copolymer-based photonic crystals without compromising processability. The nanostructured phase evolution from lamellar to hexagonal to C15 along the EO60 isopleth (ϕPEO,homo‑LiTFSI/ϕH = 0.6) is rationalized as a consequence of asymmetry in the homopolymer solubility limit for each block, which leads to exclusion of PS homopolymer from the PS-b-PEO brush prior to exclusion of the PEO homopolymer, driving increased interfacial curvature and favoring the emergence of the C15 Laves phase.

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Section: Resultsmentioning

confidence: 99%

Formation of a C15 Laves Phase with a Giant Unit Cell in Salt-Doped A/B/AB Ternary Polymer Blends

et al. 2020

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“…At r = 1/200–1/50, Li + ions show higher selectivity toward the PEO block, so that LiCl is mainly located in the PEO domains. Since the dielectric constant of PEO (7.5) is higher than that of P4VP (3.5), [ 68 ] Δ χ Born is larger than 0. Moreover, one Li + ion can complex with multiple O atoms, but the complexation strength is weak, as evidenced by the high mobility of Li + ions in PEO/Li + solid polyelectrolytes.…”

Section: Resultsmentioning

confidence: 99%

Influence of Salt Doping on the Entropy‐Driven Lower Disorder‐to‐Order Transition Behavior of Poly(ethylene oxide)‐b‐Poly(4‐vinylpyridine)

Zhang

Ding

Zhou

et al. 2021

Macro Chemistry & Physics

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Poly(ethylene oxide)‐b‐poly(4‐vinylpyridine) (PEO‐b‐P4VP) block copolymers (BCPs) exhibiting lower disorder‐to‐order transition (LDOT) phase behavior are doped with different salts (LiCl, CuCl2, and FeCl3), in which both blocks can competitively associate with the metal ions. It is found that the entropy‐driven LDOT phase behavior of PEO‐b‐P4VP can be bi‐directionally adjusted by enthalpic interactions, depending on the complexation selectivity of metal ions toward two blocks and doping ratio (r). At low rs, Li+ ions preferentially interact with PEO block, leading to a decreased disorder‐to‐order transition temperature (TDOT). Cu2+ ions selectively complex with the P4VP block, and the TDOT first increases with increasing r, followed by a decrease. By contrast, Fe3+ ions interact strongly with both blocks, resulting in increase of TDOT. At high rs, the complexation selectivity becomes weaker, leading to reduced immiscibility and increased TDOT, as compared with the hybrids with low rs. The effects of metal cation and r on the LDOT phase behavior are qualitatively explained by the change of the Flory–Huggins parameter.

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“…The efficacy of the simplification of ILs could also be somewhat anticipated because, despite the structural and chemical diversity of ILs, the Walden rule for electrolytes takes a very simple form, (molar conductivity) × (viscosity) = temperature‐dependent constant, yet the formula applies to a broad spectrum of ILs 65 . Moreover, in Reference 66, the weak‐segregation theory of Leibler with the Born solvation energy of the ions also accounted for the phase boundaries of the microphase separation of IL‐containing diblock copolymer observed by Virgilli et al 53 and Simone and Lodge, 67 treating the ions as charged spheres with the excluded volume and dielectric constant. Thus, it appears to be possible to depart from simplified models for ILs in dielectric continuums and consider a mixture of polymer and IL.…”

Section: Introductionmentioning

confidence: 99%

Polarization of ionic liquid and polymer and its implications for polymerized ionic liquids: An overview towards a new theory and simulation

Gao

Itliong

Kumar

et al. 2021

Journal of Polymer Science

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Ionic liquid (IL)‐containing polymers garner attention for electrochemical applications. This article overviews recent experimental and theoretical studies of polymer electrolytes that would be likely to cultivate new theoretical and computational frameworks for IL‐containing polymers. The first two sections outline the uniqueness of ILs that differentiates them from inorganic salts in polymers and explore deviation from the concept of the metaphor “room‐temperature molten salt.” Such distinct properties include (1) large intrinsic dipole moment and electronic polarizability, (2) hydrogen bonding, (3) π‐interactions, (4) a broad distribution of charges over the entire ion, and (5) the anisotropy of the ions. Moreover, the complexity of these properties substantially increases when the ions are polymerized. Indeed, their exceptional features would overcome the hurdle due to a trade‐off between ionic conductivity and mechanical robustness in inorganic salt‐doped polymers. Given these facts, the rest of the article focuses on emerging trends in the study of the dielectric response, phase separation, ion conductivity, and mechanical robustness of the polymer electrolytes, highlighting outstanding observations in experiments that may inspire existing theory and simulation. Our discussion also includes improving computational complexity for IL‐containing polymers. To this end, recent machine learning studies that consider ILs and polymer liquids are presented.

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Microphase Separation of Ionic Liquid-Containing Diblock Copolymers: Effects of Dielectric Inhomogeneity and Asymmetry in the Molecular Volumes and Interactions between the Cation and Anion

Cited by 10 publications

References 57 publications

Formation of a C15 Laves Phase with a Giant Unit Cell in Salt-Doped A/B/AB Ternary Polymer Blends

Formation of a C15 Laves Phase with a Giant Unit Cell in Salt-Doped A/B/AB Ternary Polymer Blends

Influence of Salt Doping on the Entropy‐Driven Lower Disorder‐to‐Order Transition Behavior of Poly(ethylene oxide)‐b‐Poly(4‐vinylpyridine)

Polarization of ionic liquid and polymer and its implications for polymerized ionic liquids: An overview towards a new theory and simulation

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