High ionic conductivity is a prerequisite for the application of solid-state polymer electrolyte towards the safe and high energy density electrochemical devices. Here we report the preparation and properties of an in-situ polymerized comb-like copolymer-based SPE (PLA/PEG-SPE) with high ionic conductivity from methyl acrylate functionalized poly(D,L-Lactide) (PLAMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA). A remarkably high ionic conductivity value of 6.9 × 10−5 S cm−1 at ambient temperature and a maximum ionic conductivity of 4.3 × 10−4 S cm−1 at 60°C were detected, with an activation energy of 0.2 eV and a Li+ transference number (tLi+) of 0.36. The PLA/PEG-SPE exhibits a wide electrochemical stability window up to 4.6 vs. Li/Li+ and very good lithium metal electrode compatibility. Solid-state LiFePO4/SPE/Li cells with integrated cathode and lithium metal deliver superior cycling stability with high discharge capacities (149 mAh g−1 as the initial specific capacity) and high capacity retention (exceeded 82% of its initial specific capacity) at 0.2 C at 60°C. The solid-state cells are also capable of being cycled at room temperature at 0.2 C. This work highlights a facile, in-situ fabrication strategy involving a vinyl-functionalized PLA precursor that yields a high-performance ion-conducting membrane attractive for lithium metal battery applications.
This
work aims to elucidate how the branching effect of macromonomer
influences the polymerization, structural features, and solution properties
of AB
n
long-subchain hyperbranched polymers
(LHPs). Our result reveals that compared with linear AB2 macromonomers, star AB3 macromonomers result in the suppression
of chain extension, and the enhancement of macromonomer self-cyclization
during the preparation of LHPs by “click” polymerization,
due to the branching-enhanced steric hindrance effect. The combined
triple-detection SEC and stand-alone LLS studies of unfractionated
and fractionated AB3 LHPs unambiguously demonstrate their
statistically fractal nature. Namely, the intrinsic viscosity ([η])
and radius of gyration (R
g) are scaled
to the macromonomer molar mass (M
macro) and the total molar mass (M
hyper) as
[η] = K
η
,AB3
M
hyper
νM
macro
μ (ν ≃ 0.39, μ ≃
0, and K
η
,AB3 ≃
0.29 mL/g) and R
g = H
R
,AB3
M
hyper
α
M
macro
β (α ≃ 0.47, β ≃ 0, and H
R
,AB3 ≃ 3.6 × 10–2 nm). Surprisingly, [η] and R
g are
both almost independent of M
macro (μ
≃ 0 ≃ β), indicating a similar draining property
and local segment density for LHPs with different subchain lengths,
which is different from the classic AB2 systems (μ
≃ 0.3 and β ≃ 0.1). A comparison of results for
AB
n
LHPs (n = 2, 3) and
short-subchain hyperbranched systems indicates that the fractal dimensions
(f) for LHPs are generally smaller than short-subchain
systems, whereas f is not sensitive to the local
segment density or branching pattern. A combination of experimental
observation and Langevin dynamics simulation of AB
n
dendrimers and LHPs further reveals (i) the segment back-folding
phenomenon is prominent only for AB
n
(n ≥ 3) LHPs systems because it is mainly dominated
by the macromonomer branching effect, rather than the internal subchain
length, and (ii) the trend for segment interpenetration increases
remarkably as M
macro increases for both
dendrimers and LHPs. The result also indicates that the unique synergistic
effect of segment back-folding and segment interpenetration in AB3 system is the most probable reason for the observed M
macro independent solution properties. Specifically,
because of the unique synergistic effect, small macromonomer/oligomer
chains can interpenetrate more easily into hyperbranched oligomer
chains composed of longer subchains and subsequently “click”
couple with the back-folded segments in the interior space of LHPs,
which eventually could lead to a similar draining property and local
segment density for AB3 LHPs with different subchain lengths.
In this article, a synthesis of N’-(benzylidene)-2-(6-methyl-1H-pyrazolo[3,4-b]quinolin-1-yl)acetohydrazides and their structural interpretation by NMR experiments is described in an attempt to explain the duplication of some peaks in their 1H- and 13C-NMR spectra. Twenty new 6-methyl-1H-pyrazolo[3,4-b]quinoline substituted N-acylhydrazones 6(a–t) were synthesized from 2-chloro-6-methylquinoline-3-carbaldehyde (1) in four steps. 2-Chloro-6-methylquinoline-3-carbaldehyde (1) afforded 6-methyl-1H-pyrazolo[3,4-b]quinoline (2), which upon N-alkylation yielded 2-(6-methyl-1H-pyrazolo[3,4-b]quinolin-1-yl)acetate (3). The hydrazinolysis of 3 followed by the condensation of resulting 2-(6-methyl-1H-pyrazolo[3,4-b]quinolin-1-yl)acetohydrazide (4) with aromatic aldehydes gave N-acylhydrazones 6(a–t). Structures of the synthesized compounds were established by readily available techniques such as FT-IR, NMR and mass spectral studies. The stereochemical behavior of 6(a–t) was studied in dimethyl sulfoxide-d6 solvent by means of 1H NMR and 13C NMR techniques at room temperature. NMR spectra revealed the presence of N’-(benzylidene)-2-(6-methyl-1H-pyrazolo[3,4-b]quinolin-1-yl)acetohydrazides as a mixture of two conformers, i.e., E(C=N)(N-N) synperiplanar and E(C=N)(N-N)antiperiplanar at room temperature in DMSO-d6. The ratio of both conformers was also calculated and E(C=N) (N-N) syn-periplanar conformer was established to be in higher percentage in equilibrium with the E(C=N) (N-N)anti-periplanar form.
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