RESUMO
The development of high-temperature supercapacitors highly relies on the explore of stable polymer electrolyte membranes (PEMs) with high ionic conductivities at high-temperature conditions. However, it is a challenge to achieve both high stability and high conductivity in a PEM at elevated temperatures. Herein, we report the fabrication of high-performance proton conductive PEMs suitable for high-temperature supercapacitors (HT-SCs), which is based on a post-assembly strategy to control the rearrangement of polymer networks in the PEMs. This strategy can create cross-linked PEMs with bicontinuous nanostructures, as well as highly stable and highly conductive features. Specifically, a series of bicontinuous PEMs are prepared by the controllable cross-linking of poly(ether-ether-ketone) and poly(4-vinylpyridine), followed by the inducement of phosphoric acid. These PEMs exhibit both a high proton conductivity of 70 mS cm-1 and a high modulus of 39.3 MPa at 150 â, which can serve as high-performance electrolytes. The HT-SCs based on these PEMs display a specific capacitance of 138.0 F g-1 and a high capacitance retention of 80.0% after 2500 galvanostatic charge-discharge cycles at 150 â, exhibiting excellent high-temperature capacitance and cycle stability. This post-assembly concept can provide a new route to design high-performance PEMs for HT-SC and other energy device applications.
RESUMO
Anion exchange membranes based on side-chain-type quarternized poly(ether ether ketone)s (QPEEKs), containing different hetero-cycloaliphatic quaternary ammonium groups, were prepared via a multi-step procedure, including polycondensation with a monomer containing pendant methylphenyl groups, bromomethylation, and followed by quaternization with 1-methylpyrrolidine (MPY), 1-methylpiperidine (MPRD), 1-methylimidazole (MIDZ) and N-methyl morpholine (MMPH), respectively. The properties of these membranes were then compared with the properties of conventional quarternized poly(ether ether ketone)s containing benzyltrimethylammonium (QPEEK-TMA). Model compounds, QMPY, QMPRD, QMIDZ and QMMPH, were synthesized and used to quantitatively compare the alkaline stability of hetero-cycloaliphatic quaternary ammonium groups using 1H NMR. The results of this study indicated that the alkaline stability of all these model compounds is in the order of QMPY > QMPRD > QTMA > QMIDZ > QMMPH. These QPEEKs membranes display superior thermal, dimensional and mechanical stability. QPEEK-TMA, QPEEK-MPY and QPEEK-MPRD exhibit higher hydroxide conductivities and lower activation energies than QPEEK-MIDZ and QPEEK-MMPH. Furthermore, after exposure to 1 M NaOH at 60 °C for 24 days, QPEEK-MPY and QPEEK-MPRD demonstrated a loss in hydroxide conductivity of 28.5% and 33.4%, respectively. Both values were lower than that of QPEEK-TMA (37.7%). Therefore, among these side-chain-type QPEEKs membranes, QPEEK-MPY and QPEEK-MPRD, containing benzylmethylpyrrolidinium and benzylmethylpiperidinium as cation head-groups, are promising AEM materials for fuel cell construction.
RESUMO
OBJECTIVE: To explore the mechanism of Toll-like receptor (TLR4) inhibition in the delay of formation of atherosclerosis by herb-partition moxibustion. METHOD: Seventy-five rabbits were randomly assigned to one of five groups: blank, atherosclerosis (AS) model, direct moxibustion, herb-partition moxibustion, and drug treatment. With the exception of the blank group, all rabbits were given a high-fat diet in addition to immunologic injury to create the AS model. The experiments were carried out for 16 weeks, at which time the aorta was removed from each rabbit. Immunohistochemical methods were used to detect the gray level of the aortic TLR4 to observe the immunologic competence of its antigens. Fluorescent quantitative polymerase chain reaction was used to detect the expression of TLR4 messenger RNA (mRNA) in the aorta. RESULTS: The gray-scale value of TLR4 and the TLR4 mRNA expression significantly decreased (p<0.05) in the direct moxibustion, herb-partition moxibustion, and drug treatment groups. Furthermore, the effects of the herb-partition moxibustion and drug treatment were superior to those of the direct moxibustion. CONCLUSION: Herb-partition moxibustion inhibits aortic TLR4 activity and mRNA expression, showing that herb-partition moxibustion delays the formation of atherosclerosis through the inhibition of TLR4 expression.