The hierarchical structures of graft-type
poly(ethylene-co-tetrafluoroethylene) (ETFE)-based
polymer electrolyte
membranes (ETFE-PEMs) were investigated using small- and ultrasmall-angle
X-ray scattering experiments. The ETFE-PEMs with ion exchange capacities
(IECs) <2.4 mmol/g possessed conducting graft domains around lamellar
crystals, with a d-spacing of 21.8–29.1 nm,
and oriented crystallites (lamellar grains) with short and long correlation
distances of 218–320 and 903–1124 nm, respectively.
The membranes with IECs > 2.7 mmol/g showed a new phase of crystallite
network domains with a d-range of 225–256
nm, indicating a phase transition from oriented crystallite to crystallite
network structures in the IEC range of 2.4–2.7 mmol/g. Noted
that for the ETFE-PEMs with high IECs higher conductivity at 30% RH
and compatible tensile strengths at 100% RH and 80 °C, compared
with Nafion, originated from the well-interconnected ion channels
around the crystallites and the remaining lamellar crystals and crystallites,
respectively.
Hydrous ruthenium oxide (RuO 2 •nH 2 O) has inherent proton−electron mixed-conductive nature and offers huge pseudocapacitance (>700 F g −1 ), having attracted the attention of many capacitor engineers. However, the origin of the anomalous pseudocapacitance, exhibiting a strong maximum at a specific narrow optimum annealing temperature of ca. 150 °C, has yet to be understood. Here we show a longawaited explanation for this mystery based on its hierarchical nanostructure unveiled by small-angle X-ray scattering (SAXS). The striking contrast in X-ray atomic scattering factors enables SAXS to exclusively probe heavy RuO 2 in subnanoto nanoscale, dispersed in confined water. We demonstrate that the surface area of the first aggregate of subnano primary RuO 2 particles dominates the accessible number of proton and hence pseudocapacitance, providing critical insights into the nanoarchitectural design of high-performance electrodes for electrochemical capacitors.
α-Crystallin possesses a dynamic quaternary structure mediated by its subunit dynamics. Elucidation of a mechanism of subunit dynamics in homo-oligomers of αB-crystallin was tackled through deuteration-assisted small-angle neutron scattering (DA-SANS) and electrospray ionization (ESI) native mass spectrometry (nMS). The existence of subunit exchange was confirmed with DA-SANS, and monomers liberated from the oligomers were observed with nMS. With increasing temperature, an increase in both the exchange rate and monomer population was observed despite the absence of oligomer collapse. It is proposed that transiently liberated subunits, namely, “traveling subunits,” play a role in subunit exchange. Moreover, we propose that protein function is regulated by these traveling subunits.
Nucleosomes containing a human histone variant, H2A.B, in an aqueous solution were analyzed by small-angle neutron scattering utilizing a contrast variation technique. Comparisons with the canonical H2A nucleosome structure revealed that the DNA termini of the H2A.B nucleosome are detached from the histone core surface, and flexibly expanded toward the solvent. In contrast, the histone tails are compacted in H2A.B nucleosomes compared to those in canonical H2A nucleosomes, suggesting that they bind to the surface of the histone core and/or DNA. Therefore, the histone tail dynamics may function to regulate the flexibility of the DNA termini in the nucleosomes.
The microstructures and chemical composition of nano-precipitates in vanadium (V) steels were investigated by the alloy contrast variation method (ACV) using small-angle X-ray scattering (SAXS) coupled with small-angle neutron scattering (SANS) at holding temperatures ranging between 600 and 700°C. Both the SAXS and SANS profiles exhibited clear scattering, depending on the holding temperature, due to the presence of nano-precipitates. The scattering profiles of the precipitates are characteristic of spherical or disc-like particles. The average diameters of these precipitates increased from 0.5 nm at 600°C to 23 nm at 700°C, whereas the number density of the precipitates decreases with increased holding temperature. Therefore, the increasing holding temperature results in an increase in the growth rate of the precipitates. ACV analysis revealed that the chemical composition of the precipitates corresponds to NaCl-type vanadium carbide (VC) at 675 and 700°C, and as VC0.9 at 625 and 650°C. The formation of a different heterogeneity, non-NaCl type, was found in the sample at a holding temperature of 600°C. This probably corresponds to a precursor of the NaCl phase in the initial process of precipitation.
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