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.
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.
Hydroquinone has been used for decades as a skin lightening agent. Its use in cosmetics has been banned as a result of skin problems including contact dermatitis and ochronosis. A total of 22 samples of different skin whitening cosmetics were collected from local market. They were analyzed by using thin layer chromatography and HPLC for qualitative and quantitative determination of their hydroquinone contents. The hydroquinone was extracted from samples by using 96% ethanol and was subjected to TLC analysis. Eleven out of 22 samples were found to contain hydroquinone. The HPLC analysis showed the concentration of hydroquinone ranged from 0.002% to 0.092% in the cosmetic samples.
Solid polymer electrolytes (SPE) are of great importance for developing the next-generation all-solid-state lithium metal batteries, which are featured by their high safety and extraordinary energy density. Herein, by using the highly efficient azide-alkyne click chemistry, a series of long-subchain hyperbranched copolymers from various compositions of AB 2 macromonomers of PCL-2N 3 (polycaprolactone) and PS-2N 3 (polystyrene) were synthesized and employed as SPE polymer host. Taking advantage of the hyperbranched structure, the crystallization of PCL was successfully suppressed, and endows the SPE with high ionic conductivity and high mechanical properties simultaneously. By doping with LiFSI, the SPEs thereof exhibit high ionic conductivity (1.59 × 10 −4 S cm −1 at 80 °C), broad electrochemical stability window (>4.6 V) and high lithium-ion transference number (>0.40). The electrolyte film based on the HB-II (the hyperbranched PCL/PS copolymer with 70 wt% PCL and 30 wt% PS) shows an ionic conductivity of 1.36 × 10 −5 S•cm −1 at 80 °C and a high lithium transference number of 0.49. The all-solid-state LiFePO 4 //Li cell with HB-II-based SPE delivers a high and stable discharge capacity (133 mAh•g −1 at 1 C, with 90% capacity retention after 300 cycles) and exhibits long lifetime up to over 1200 cycles, owing to its relatively high ionic conductivity and good interfacial stability.
Water purification is very necessary to provide clean and quality water to all livings for their survival. Various techniques for water treatment is in use now a days. The most common and useable method is the adsorption. The activated carbons generated from different ingredients like walnut shell, bagasse and the rice husk. The adsorbent generated from activated carbon can be efficiently utilized for municipal wastewater to be treated to reduce TSS, TDS, COD, turbidity, EC, pH and Temperature. These activated carbons occur naturally and environmentally friendly. Also, no bad effect on humans. Mostly used for the treatment of municipal wastewater. Walnut Shell, Bagasse and Rice Husk conversion to activated carbon minimizing the cost of waste transfer and gives cheap resources for generation of activated carbon.
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