We demonstrate enhanced Li+ transport through the selectively solvated ionic layers of a single-ion conducting polymer. The polymer is a precisely segmented ion-containing multiblock copolymers with well-defined Li+SO3– ionic layers between crystallized linear aliphatic 18-carbon blocks. X-ray scattering reveals that the dimethyl sulfoxide (DMSO) molecules selectively solvate the ionic layers without disrupting the crystallization of the polymer backbone. The amount of DMSO (∼21 wt %) calculated from the increased layer spacing is consistent with thermogravimetric analysis. The ionic conductivity through DMSO-solvated ionic layers is >104 times higher than in the dried state, indicating a significant enhancement of ion transport in the presence of this solvent. Dielectric relaxation spectroscopy (DRS) further elucidates the role of the structural relaxation time (τ) and the number of free Li+ (n) on the ionic conductivity (σ). Specifically, DRS reveals that the solvation of ionic domains with DMSO contributes to both accelerating the structural relaxation and the dissociation of ion pairs. This study is the initial demonstration that selective solvation is a viable design strategy to improve ionic conductivity in nanophase separated, single-ion conducting multiblock copolymers.
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Nanoscale layers of precise ion-containing polyamides with lithiated phenyl sulfonate in the polymer backbone
We investigate a new series of precise ion-containing polyamide sulfonates (PAS x Li), where a short polar block precisely alternates with a non-polar block of aliphatic carbons ( x = 4, 5, 10, or 16) to form an alternating (AB) n multiblock architecture. The polar block includes a lithiated phenyl sulfonate in the polymer backbone. These PAS x Li polymers were synthesized via polycondensation of diaminobenzenesulfonic acid and alkyl diacids (or alkyl diacyl chlorides) with x -carbons, containing amide bonds at the block linkages. The para - and meta -substituted diaminobenzene monomers led to polymer analogs denoted p PAS x Li and m PAS x Li, respectively. When x ≤ 10, the para -substituted diamine monomer yields multiblock copolymers of a higher degree of polymerization than the meta -substituted isomer, due to the greater electron-withdrawing effect of the meta -substituted monomer. The PAS x Li polymers exhibit excellent thermal stability with less than 5% mass loss at 300 °C and the glass transition temperatures ( T g ) decrease with increasing hydrocarbon block length ( x ). Using the random phase approximation, the Flory–Huggins interaction parameter ( χ ) is determined for p PAS10Li, and χ (260 °C) ∼ 2.92 reveals high incompatibility between the polar ionic and non-polar hydrocarbon blocks. The polymer with the longest hydrocarbon block, p PAS16Li, is semicrystalline and forms well-defined nanoscale layers with a spacing of ∼2.7 nm. Relative to previously studied polyester multiblock copolymers, the amide groups and aromatic rings permit the nanoscale layers to persist up to 250 °C and thus increase the stability range for ordered morphologies in precise ion-containing multiblock copolymers.
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- NSF-PAR ID:
- 10415008
- Date Published:
- Journal Name:
- Polymer Chemistry
- Volume:
- 13
- Issue:
- 41
- ISSN:
- 1759-9954
- Page Range / eLocation ID:
- 5811 to 5819
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d2py00802e
