Supertwisted Chiral Gyroid Mesophase in Chiral Rod-Like Compounds.

Among the intriguing bicontinuous self-assembled structures, the gyroid cubic is the most ubiquitous. It is found in block and star polymers, surfactants with or without solvent, in thermotropic liquid crystals with end- or side-chains, and in biosystems providing structural color and modelling cell mitosis. It contains two interpenetrating networks of opposite chirality and is thus achiral if, as usual, the content of the two nets is the same. However, we now find that this is not the case for strongly chiral compounds. While achiral molecules follow the opposite twists of nets 1 and 2, molecules with a chiral center in their rod-like core fail to follow the 70° twist between junctions in net 2 and instead wind against it by -110° to still match the junction orientation. The metastable chiral gyroid is a high-entropy high-heat-capacity mesophase. The homochirality of its nets makes the CD signal of the thienofluorenone compounds close to that in the stable I23 phase with 3 isochiral nets.

Designing a Magnesium/Sodium Hybrid Battery Using Hierarchical Iron Selenide Architecture as Cathode Material and Modified Dual-Ion Salts in Ether as Electrolyte.

We developed a magnesium/sodium (Mg/Na) hybrid battery using a hierarchical disk-whisker FeSe2 architecture (HD-FeSe2) as the cathode material and a modified dual-ion electrolyte. The polarizable Se2- anion reduced the Mg2+ migration barrier, and the 3D configuration possessed a large surface area, which facilitated both Mg2+/Na+ cation diffusion and electron transport. The dual-ion salts with NaTFSI in ether reduced the Mg plating/stripping overvoltage in a symmetric cell. The hybrid battery exhibited an energy density of 260.9 Wh kg-1 and a power density of 600.8 W kg-1 at 0.2 A g-1. It showed a capacity retention of 154 mAh g-1 and a Coulombic efficiency of over 99.5% under 1.0 A g-1 after 800 long cycles. The battery also displayed outstanding temperature tolerance. The findings of 3D architecture as cathode material and hybrid electrolyte provide a pathway to design a highly reliable Mg/Na hybrid battery.

4'-O-methylbavachalcone alleviates ischemic stroke injury by inhibiting parthanatos and promoting SIRT3.

Cerebral ischemia-reperfusion injury (CIRI) can induce massive death of ischemic penumbra neurons via oxygen burst, exacerbating brain damage. Parthanatos is a form of caspase-independent cell death involving excessive activation of PARP-1, closely associated with intense oxidative stress following CIRI. 4'-O-methylbavachalcone (MeBavaC), an isoprenylated chalcone component in Fructus Psoraleae, has potential neuroprotective effects. This study primarily investigates whether MeBavaC can act on SIRT3 to alleviate parthanatos of ischemic penumbra neurons induced by CIRI. MeBavaC was oral gavaged to the middle cerebral artery occlusion-reperfusion (MCAO/R) rats after occlusion. The effects of MeBavaC on cerebral injury were detected by the neurological deficit score and cerebral infarct volume. In vitro, PC-12 cells were subjected to oxygen and glucose deprivation/reoxygenation (OGD/R), and assessed cell viability and cell injury. Also, the levels of ROS, mitochondrial membrane potential (MMP), and intracellular Ca2+ levels were detected to reflect mitochondrial function. We conducted western blotting analyses of proteins involved in parthanatos and related signaling pathways. Finally, the exact mechanism between the neuroprotection of MeBavaC and parthanatos was explored. Our results indicate that MeBavaC reduces the cerebral infarct volume and neurological deficit scores in MCAO/R rats, and inhibits the decreased viability of PC-12 cells induced by OGD/R. MeBavaC also downregulates the expression of parthanatos-related death proteins PARP-1, PAR, and AIF. However, this inhibitory effect is weakened after the use of a SIRT3 inhibitor. In conclusion, the protective effect of MeBavaC against CIRI may be achieved by inhibiting parthanatos of ischemic penumbra neurons through the SIRT3-PARP-1 axis.

Quantitative Model of Multiple Crystal Growth Rate Minima in Polymers with Regularly Spaced Substituent Groups.

A simple theory has been developed to explain quantitatively the multiple crystal growth rate minima observed experimentally in polyethylene brassylates (PEBs), polymers with regularly spaced "chemical defects", in this case, diester groups separated by 11 methylenes. The minima occur at the transitions where the fold length drops from 4 to 3 repeat units and from 3 to 2 units. An analytical rate-equation model was developed with elementary attachment and detachment steps of individual monomer repeat units, also including postattachment stem lengthening (stem conversion). The model produced a good fit to experimental crystallization rate curves for PEBs of three different molecular weights. The fits confirm in a quantitative way that the anomalies are caused by the self-poisoning effect, as proposed in the original experimental report on PEBs, based on the ideas developed in previous studies on long-chain n-alkanes. It is concluded that the rate minima in PEBs are the result of temporary attachment to the growth surface of stems that are too short to be stable yet long enough and close to stability to obstruct productive growth by stems of sufficient length. The results confirm the ubiquitous presence of self-poisoning at the growth front of polymer crystals in general and will help to achieve a better understanding of the complex process of crystallization of polymers. It will also allow the determination of more realistic parameters controlling their lamellar growth kinetics.

Continuous Spectrum of Morphologies and Phase Behavior across the Contact Zone from Poly(l-lactide) to Poly(d-lactide): Stereocomplex, Homocrystal, and Between.

The enantiomeric ratio is a key factor affecting the crystallization behavior and morphology of poly-l-lactide/poly-d-lactide (PLLA/PDLA) blends. Despite a number of studies on crystallization of nonequimolar PLLA/PDLA blends, a full picture of the effect of the L/D ratio is still lacking. Here, we put the two enantiomers in contact and allow interdiffusion above the melting point of the stereocomplex crystal (SC) to prepare samples with a continuously changing L/D ratio from enantiopure PLLA (ratio 0/100) to enantiopure PDLA (100/0). Using polarized optical microscopy, atomic force microscopy, and microbeam X-ray diffraction, the continuous spectrum of morphologies and phase behaviors across the contact zone is investigated. The blend morphology shows clear evidence of "poisoning by purity" of SC crystallization at all blend compositions. The low birefringence of the 50/50 SC is found to be due to the meandering of broken edge-on lamellae. Its further decrease to near zero as L/D deviates further away from 50/50 is explained by transition from radial edge-on lamellae to fully random meandering lamellae, then to mixed flat-on lamellae, and finally to submicron-sized axialites. In comparison with the smooth and straight homocrystal (HC) lamellae of pure enantiomers, the lamellae in the blends often have serrated edges caused by pinning by rejected excess enantiomer acting as an impurity during lamellar growth. A feature of the binary phase diagram is pure enantiomers acting as an impurity to the SC and counter-enantiomer acting as an impurity to homocrystallization of the enantiomers. Crystallization was found to be most suppressed at 99% enantiomeric purity, where the amount of the counter-enantiomer is insufficient for creation of SC nuclei and HC growth is inhibited by the small amount of the enantio-impurity. These and other intriguing results are less likely to be noticed without the continuous composition gradient of the contact sample.

3D Morphology of Different Crystal Forms in ß-Nucleated and Fiber-Sheared Polypropylene: α-Teardrops, α-Teeth, and ß-Fans.

Polymorphism of semicrystalline polymers has significant influence on their physical properties, with each form having its advantages and disadvantages. However, real-life polymer processing often results in different coexisting crystal polymorphs, and it remains a challenge to determine their shape, spatial distribution, and volume fraction. Here, i-polypropylene (i-PP) sheets containing both α- and ß-forms were prepared either by adding ß-nucleating agent or by fiber pulling-induced crystallization. By adding a compatible dye that is partially rejected from the growing crystalline aggregates (spherulites and cylindrites), we visualize the shape of these objects in 3D using two-photon fluorescence confocal microscopy. To distinguish between crystal forms, we take advantage of the difference in dye-retaining ability of the α- and ß-aggregates. Even in 2D, fluorescence microscopy (FM) distinguishes the two crystal forms better than polarized microscopy. In 3D imaging, the volume fraction and spatial distribution of α- and ß-forms in different morphological types could be determined quantitatively. Morphologies described as α-teeth, ß-fans, and α-teardrops were visualized for the first time in 3D. Furthermore, internal and surface microcracks were seen to be associated predominantly with the ß-form and around the fiber. Spatial distribution of α- and ß-forms was also determined by scanning with a synchrotron X-ray beam. Good agreement was obtained with 3D microscopy, but XRD could not match the detail obtainable by the tomography. The work demonstrates the ability of the 3D imaging method to distinguish different crystal forms and their specific morphologies.

Enantiomers Self-Sort into Separate Counter-Twisted Ribbons of the Fddd Liquid Crystal─Antiferrochirality and Parachirality.

The recently discovered orthorhombic liquid crystal (LC) phase of symmetry Fddd is proving to be widespread. In this work, a chiral hydroxybutyrate linkage is inserted into the molecular core of hexacatenar rodlike compounds, containing a thienylfluorenone fluorophore. In addition to more usual tools, the methods used include grazing-incidence X-ray scattering, modulated differential scanning calorimetry (DSC), flash DSC with rates up to 6000 K/s, and chiro-optical spectroscopies using Mueller matrix method, plus conformational mapping. Although pure R and S enantiomers form only a strongly chiral hexagonal columnar LC phase (Colh*), the racemic mixture forms a highly ordered Fddd phase with 4 right- and 4 left-handed twisted ribbon-like columns traversing its large unit cell. In that structure, the two enantiomers locally deracemize and self-sort into the columns of their preferred chirality. The twisted ribbons in Fddd, with a 7.54 nm pitch, consist of stacked rafts, each containing ∼2 side-by-side molecules, the successive rafts rotated by 17°. In contrast, an analogous achiral compound forms only the columnar phase. The multiple methods used gave a comprehensive picture and helped in-depth understanding not only of the Fddd phase but also of the "parachiral" Colh* in pure enantiomers with irregular helicity, whose chirality is compared to the magnetization of a paramagnet in a field. Unusual short-range ordering effects are also described. An explanation of these phenomena is proposed based on conformational analysis. Surprisingly, the isotropic-columnar transition is extremely fast, completing within ∼20 ms. A clear effect of phase on UV-vis absorption and emission is observed.

Rational engineering NiMoO4nanosheets or Mn3O4nanowires on Fe2O3microdiscs as novel hierarchical anodes for high-performance lithium-ion batteries.

Since current graphite-based lithium-ion battery anode has a low theoretical capacity, the development of high-performance lithium-ion battery is severely restricted. Here, novel hierarchical composites composing of microdisc and the secondarily grown nanosheets and nanowires are developed, taking NiMoO4nanosheets and Mn3O4nanowires growing on Fe2O3microdiscs as demonstrating examples. The growth processes of the hierarchical structures have been investigated by adjusting a series of preparation conditions. The morphologies and structures have been characterized by using scanning electron microscopy, transmission electron microscope and x-ray diffraction. Fe2O3@Mn3O4composite-based anode displays a capacity of 713 mAh g-1after 100 cycles at 0.5 A g-1with a high Coulombic efficiency. A good rate-performance is also achieved. Fe2O3@NiMoO4anode delivers 539 mAh g-1after 100 cycles at 0.5 A g-1, which is obviously higher than that of pure Fe2O3. The hierarchical structure is conducive to improve the transport of electrons and ions, and provide numerous active sites, thus significantly enhancing the electrochemical performance. Moreover, the electron transfer performance is investigated by using density functional theory calculations. It is expected the findings presented here and the rational engineering of nanosheets/nanowires on microdiscs would be applicable for developing many other high-performance energy-storage composites.

A columnar liquid quasicrystal with a honeycomb structure that consists of triangular, square and trapezoidal cells.

Quasicrystals are intriguing structures that have long-range positional correlations but no periodicity in real space, and typically with rotational symmetries that are 'forbidden' in conventional periodic crystals. Here, we present a two-dimensional columnar liquid quasicrystal with dodecagonal symmetry. Unlike previous dodecagonal quasicrystals based on random tiling, a honeycomb structure based on a strictly quasiperiodic tessellation of tiles is observed. The structure consists of dodecagonal clusters made up of triangular, square and trapezoidal cells that are optimal for local packing. To maximize the presence of such dodecagonal clusters, the system abandons periodicity but adopts a quasiperiodic structure that follows strict packing rules. The stability of random-tiling dodecagonal quasicrystals is often attributed to the entropy of disordering when strict tiling rules are broken, at the sacrifice of the long-range positional order. However, our results demonstrate that quasicrystal stability may rest on energy minimization alone, or with only minimal entropic intervention.

Morphology of Shear-Induced Polymer Cylindrites Revealed by 3D Optical Imaging.

Two-photon confocal laser microscopy was used to obtain three-dimensional (3D) images of the morphology of poly(lactic acid) after shear-induced crystallization. The necessary fluorescence contrast was achieved by doping the polymer with Nile Red. The dye gets partially rejected from the growing crystalline aggregates during their formation, thus creating a renderable high-low fluorescence boundary outlining the shape of the aggregates. Parallel-plate melt-shearing and pulling a glass fiber through the melt were used as the two methods to achieve shear-induced crystallization. This study focuses on the shape of the resulting cylindrites, i.e., large-diameter shish-kebabs. The first 3D images of polymer cylindrites show that, if far from boundaries, they are circular cylinders, highly regular after fiber pull, but less so after parallel-plate shear. In the latter case, the cylindrite reveals the trajectory of the foreign particle that had nucleated its growth. Interestingly, lateral growth of the cylindrites was found to accelerate toward the sample surface when approaching it, giving the cylindrite an elliptical cross section. Furthermore and surprisingly, in the case of fiber pull, a row of spherulites is nucleated at the polymer-substrate interface nearest to the fiber, aligned along the fiber axis and appearing ahead of the rest of the space-filling spherulites. Both the phenomena, elliptical cylindrites and row of spherulites, are attributed to negative pressure buildup peaking at the cylindrite growth front and at the nearby film surface caused by crystallization-induced volume contraction. The pressure and flow distribution in the system is confirmed by numerical simulation. The results illustrate the value of 3D imaging of crystalline morphology in polymer science and polymer processing industry.

Essential oil of Magnolia denudata is an effective anesthetic for spotted seabass (Lateolabrax maculatus): a test of its effect on blood biochemistry, physiology, and gill morphology.

Magnolia denudata is a well-known ornamental tree in China due to its beautiful blossoms, and it has been used as an analgesic to treat human headaches. This study investigated the anesthetic potential and physiological response of the essential oil of M. denudata flowers on spotted seabass Lateolabrax maculatus. Fish (mean ± SD, 164.16 ± 15.40 g) were individually exposed to different concentrations of M. denudata essential oil (MDO, 10, 20, 40, 60, 80, 100, and 120 mg/L) and eugenol (10, 20, 30, 40, 50, 60, and 70 mg/L) to investigate anesthetic efficacy. Based on the ideal time criterion for anesthetic induction (< 3 min) and recovery (< 10 min), the lowest effective concentration for spotted seabass was 100 mg/L for MDO and 60 mg/L for eugenol. The physiological and histopathological damage in the gill of L. maculatus after using MDO and eugenol was also evaluated at the minimum dose inducing deep anesthesia, and at 0, 6, and 24 h after recovery. The results showed that MDO and eugenol anesthesia alleviated the levels of cortisol and glucose and the lactic dehydrogenase activity induced by handling. Compared with eugenol, MDO also caused secondary stress to the body, but MDO caused minor physiological responses and histological changes in the gills. This study suggests that MDO is an effective anesthetic for spotted seabass.

A case of antiferrochirality in a liquid crystal phase of counter-rotating staircases.

Helical structures continue to inspire, prompted by examples such as DNA double-helix and alpha-helix in proteins. Most synthetic polymers also crystallize as helices, which relieves steric clashes by twisting, while keeping the molecules straight for their ordered packing. In columnar liquid crystals, which often display useful optoelectronic properties, overall helical chirality can be induced by inclusion of chiral chemical groups or dopants; these bias molecular twist to either left or right, analogous to a magnetic field aligning the spins in a paramagnet. In this work, however, we show that liquid-crystalline columns with long-range helical order can form by spontaneous self-assembly of straight- or bent-rod molecules without inclusion of any chiral moiety. A complex lattice with Fddd symmetry and 8 columns per unit cell (4 right-, 4 left-handed) characterizes this "antiferrochiral" structure. In selected compounds it allows close packing of their fluorescent groups reducing their bandgap and giving them promising light-emitting properties.

Bowls, vases and goblets-the microcrockery of polymer and nanocomposite morphology revealed by two-photon optical tomography.

On the >1 µm scale the morphology of semicrystalline plastics like polyethylene or Nylon features spherulites, "shish-kebabs", cylinddrites and other crystalline aggregates which strongly affect mechanical and other material properties. Current imaging techniques give only a 2D picture of these objects. Here we show how they can be visualized in 3D using fluorescent labels and confocal microscopy. As a result, we see spherulites in 3D, both in neat polymers and their nanocomposites, and observe how unevenly nanoparticles and other additives are distributed in the material. Images of i-polypropylene and biodegradable poly(lactic acid) reveal previously unsuspected morphologies such as "vases" and "goblets", nonspherical "spherulites" and, unexpectedly, "shish-kebabs" grown from quiescent melt. Also surprisingly, in nanocomposite sheets spherulite nucleation is seen to be copied from one surface to another, mediated by crystallization-induced pressure drop and local melt-flow. These first results reveal unfamiliar modes of self-assembly in familiar plastics and open fresh perspectives on polymer microstructure.

Gyroid-Nanostructured All-Solid Polymer Films Combining High H+ Conductivity with Low H2 Permeability.

Gyroid-nanostructured all-solid polymer films with exceedingly high proton conductivity and low H2 gas permeability have been created via crosslinking polymerization of mixtures of a zwitterionic amphiphilic monomer and a polymerizable imide-type acid that co-organize into bicontinuous cubic liquid-crystalline phases. The gyroid nanostructures are visualized by reconstructing a 3D electron map from the synchrotron X-ray diffraction patterns. These films exhibit high proton conductivity of the order of 10-1 S cm-1 and extremely low H2 gas permeability of the order of 10-15 mol m m-2 s-1 Pa-1 . These properties can be ascribed to the presence of the ionic liquid-like layer along the gyroid minimal surface. Since these two characteristics are required for improving the performance of proton-exchange membrane fuel cells, the present membrane design represents a promising strategy for the development of advanced devices, pertinent to establishing sustainable energy sources.

Retina Vascular Perfusion Dynamics During Exercise With and Without Face Masks in Healthy Young Adults: An OCT Angiography Study.

Purpose: To determine possible impacts on retinal microvasculature in healthy young adults during exercise with a face mask, using optical coherence tomography angiography (OCTA). Methods: Twenty-three healthy participants (23 eyes, 17 women and 6 men) performed the incremental continuous running test (ICRT) with different masks. OCTA of the macula and optic nerve head were performed before and after ICRT to detect changes in retinal vessel density (VD). All participants were in groups A, B, and C (before ICRT) and groups A', B', and C' (after ICRT), which comprised data from volunteers without a mask, with a surgical mask, and with an N95 mask, respectively. Results: Before ICRT, group C showed significantly reduced VD in the superficial plexus (SP), except foveal VD, compared with group A (P < 0.05). After ICRT, groups B' and C' showed significantly shorter maximum running time, lower oxygen saturation, and lower perifoveal VD of SP compared with group A' (P < 0.05). Conclusions: Use of an N95 mask reduced VD in SP even under quiescent conditions, which might have clinical implications for protecting healthy workers and indoor manual labor workers from potential risks of retinal damage due to long-term mask use. Moreover, mask use while exercising might lead to attenuated exercise ability and lower VD in SP, which should be investigated in additional studies. Translational Relevance: Retina vascular perfusion dynamics could be monitored in vivo by OCTA, which would be valuable to study physiologic retinal blood flow redistribution and potential impacts on retinal vascular perfusion during exercise with face masks.

Quasi-continuous melting of model polymer monolayers prompts reinterpretation of polymer melting.

Condensed matter textbooks teach us that melting cannot be continuous and indeed experience, including with polymers and other long-chain compounds, tells us that it is a strongly first-order transition. However, here we report nearly continuous melting of monolayers of ultralong n-alkane C390H782 on graphite, observed by AFM and reproduced by mean-field theory and MD simulation. On heating, the crystal-melt interface moves steadily and reversibly from chain ends inward. Remarkably, the final melting point is 80 K above that of the bulk, and equilibrium crystallinity decreases continuously from ~100% to <50% prior to final melting. We show that the similarity in melting behavior of polymers and non-polymers is coincidental. In the bulk, the intermediate melting stages of long-chain crystals are forbidden by steric overcrowding at the crystal-liquid interface. However, there is no crowding in a monolayer as chain segments can escape to the third dimension.

Extraordinary Acceleration of Cogwheel Helical Self-Organization of Dendronized Perylene Bisimides by the Dendron Sequence Encoding Their Tertiary Structure.

The cogwheel model of hierarchical self-organization provides a route to highly ordered crystalline helical columnar hexagonal arrays of perylene bisimides (PBIs) conjugated to (3,4,5)-dimethyloctyl (racemic dm8*, r) minidendrons. Cogwheel PBIs assemble with identical structural order irrespective of molecular chirality to generate helical columns jacketed with an alkyl coat with length equal to half the helical pitch, exhibiting helical deracemization in the crystal state. These assemblies were accessible only via annealing or cooling and reheating at 1 °C/min. Recently it was discovered that hybrid rr8 sequence-defined dendrons with r and linear n-octyl (8) chains enabled the formation of the cogwheel phase at 10 °C/min upon heating but not cooling. Here we report four libraries of hybrid PBIs with sequence-defined dendrons containing r and n-alkyl (CnH2n+1) chains with n = 6, 7, 9, and 10. Structural analysis of these libraries by fiber X-ray diffraction and differential scanning calorimetry reveals that the 9r9 sequence enables an extraordinary acceleration of cogwheel assembly at rates of up to 50 °C/min on heating and cooling, providing, to the best of our knowledge, the fastest crystallizing supramolecular or covalent macromolecule known. Solid-state NMR studies help to elucidate this unexpected and unprecedented extraordinary acceleration of hierarchical self-organization, which arises from a combination of crystal packing of the ideal tertiary structure and alkyl chain dynamics. This general model raises questions about the use of achiral motifs to achieve high structural order in chiral systems and the need for disorder to create order in complex biological and bioinspired synthetic systems.

Double-Gyroid Nanostructure Formation by Aggregation-Induced Atropisomerization and Co-Assembly of Ionic Liquid-Crystalline Amphiphiles.

We report a new molecular-design principle for creating double-gyroid nanostructured molecular assemblies based on atropisomerization. Ionic amphiphiles containing two imidazolium rings close to each other were designed and synthesized. NMR data revealed that the rotation of the imidazolium rings is restricted, with an activation energy as high as 63 kJ mol-1 in DMSO-d6 solution (DFT prediction for a model compound in the vacuum: 90-100 kJ mol-1 ). Due to the restricted rotation, the amphiphiles feature "double" atropisomeric axes in their ionic segments and form three stable atropisomers: meso, R, and S. These isomers co-organize into I a 3 ‾ d -type bicontinuous cubic liquid-crystalline mesophases through nanosegregation of the ionic and non-ionic parts. Considering the intrinsic characteristic of I a 3 ‾ d -type bicontinuous cubic structures that they are composed of intertwined right- and left-handed single gyroids, we propose that the simultaneous presence of both R- and S-atropisomers is an important contributor to the formation of double-gyroid structures.

Liquid Organic Frameworks: The Single-Network "Plumber's Nightmare" Bicontinuous Cubic Liquid Crystal.

Novel bolapolyphiles, built of a p-terphenyl or bistolane core with polar glycerol end-groups and two laterally attached n-alkyl or semiperfluoroalkyl chains, form the first "single plumber's nightmare network", the simplest soft-matter cubic phase (Pm3̅m). Its cage-like grid comprises bundles of aromatic rods lying along the cubic unit cell edges, connected by six-way hydrogen-bonded junctions. Side-chains fill the remaining volume of this unique noninterpenetrating liquid-crystalline organic framework.

A self-assembled liquid crystal honeycomb of highly stretched (3-1-1)-hexagons.

A new liquid crystalline honeycomb phase is reported, containing highly stretched giant hexagonal cells with two opposing walls spanned by three consecutive end-to-end H-bonded rods, the (3-1-1) hexagons.