Synthesis of Triblock Polycarboxylate Superplasticizers with Well-Defined Structure and Its Dispersing Performance in ß-Hemihydrate Gypsum.

In this work, a novel AaBAb-type triblock polycarboxylate superplasticizers (PCEs) with well defined molecular structures were designed and synthesized, firstly, by reversible addition-fragmentation chain transfer (RAFT) polymerization, to explore the structure-property relationship PCEs in the ß-hemihydrate gypsum (ß-HH) system. Three PCEs with the same molecular weight and different structure were obtained by changing the feed ratio of the RAFT agent, initiator, and monomer. The effect of the chemical structure of PCEs on their dispersing property and water reduction capacity were assessed in gypsum by measuring the flowability of pastes and the adsorption ability of PCEs on gypsum. Results showed that among three PCEs, when the monomer ratio is 5:1 and a:b = 1:1, PCE-1 exhibited a higher working efficiency, verifying the contribution of regulating structural parameters to the improvement in performances of gypsum paste, because PCE-1 showed the strongest binding capacity with calcium ions due to the relatively equal amount of carboxyl groups at both ends. The AaBAb-type PCEs provide a special advantage over the conventional comb polymer to understand the relation between the structure and property of PCEs, and a direction for further development of PCEs of high performance.

Reaction Mechanism of CO2 and Styrene Oxide Catalyzed by Ionic Liquids: A Combined DFT Calculation and Experimental Study.

Bioactive compound 3-aryl-2-oxazolidinone could be synthesized by a green method mixing carbon dioxide, aniline, and ethylene oxide. Our group previously proposed a parallel mechanism for this conversion catalyzed by ionic liquids. Recently, a new study on a similar reaction system of styrene oxide, carbon dioxide, and aniline under the catalysis of K3PO4 gave a different serial mechanism. In order to explore the mechanism of reaction, we conducted a combined theoretical and experimental study on a one-pot conversion of styrene oxide, carbon dioxide, and aniline. In experiments, two isomer products, 3,5-diphenyl-l,3-oxazolidin-2-one and 3,4-diphenyl-l,3-oxazolidin-2-one, were observed. The computational results show that the parallel mechanism is more favored in thermodynamics and in kinetics due to the instability of isocyanate and hardness of its generation. Hence, we believe the previous parallel mechanism is more reasonable under our catalysts and conditions.

Interface Engineering V2 O5 Nanofibers for High-Energy and Durable Supercapacitors.

A local electric field is induced to engineer the interface of vanadium pentoxide nanofibers (V2 O5 -NF) to manipulate the charge transport behavior and obtain high-energy and durable supercapacitors. The interface of V2 O5 -NF is modified with oxygen vacancies (Vö) in a one-step polymerization process of polyaniline (PANI). In the charge storage process, the local electric field deriving from the lopsided charge distribution around Vö will provide Coulombic forces to promote the charge transport in the resultant Vö-V2 O5 /PANI nanocable electrode. Furthermore, an ≈7 nm porous PANI coating serves as the external percolated charge transport pathway. As the charge transfer kinetics are synergistically enhanced by the dual modifications, Vö-V2 O5 /PANI-based supercapacitors exhibit an excellent specific capacitance (523 F g-1 ) as well as a long cycling lifespan (110% of capacitance remained after 20 000 cycles). This work paves an effective way to promote the charge transfer kinetics of electrode materials for next-generation energy storage systems.

Are Ionic Liquids Chemically Stable?

Ionic liquids have attracted a great deal of interest in recent years, illustrated by their applications in a variety of areas involved with chemistry, physics, biology, and engineering. Usually, the stabilities of ionic liquids are highlighted as one of their outstanding advantages. However, are ionic liquids really stable in all cases? This review covers the chemical stabilities of ionic liquids. It focuses on the reactivity of the most popular imidazolium ionic liquids at structural positions, including C2 position, N1 and N3 positions, and C4 and C5 positions, and decomposition on the imidazolium ring. Additionally, we discuss decomposition of quaternary ammonium and phosphonium ionic liquids and hydrolysis and nucleophilic reactions of anions of ionic liquids. The review aims to arouse caution on potential decomposition of ionic liquids and provides a guide for better utilization of ionic liquids.

First-principles study of VPO4O as a cathode material for rechargeable Mg batteries.

The electrochemical properties of VPO4O as a cathode for Mg batteries were studied by performing first principles calculations. Mg insertion features a plateau at about 2.8 V up to Mg0.5VPO4O and then another plateau at around 2.2 V up to MgVPO4O, with a theoretical capacity of about 154 mA h g-1 and 144 mA h g-1, respectively. MgVPO4O is found to be dynamically stable with the absence of negative frequencies in the phonon density of states. The insertion of one Mg reduced two VO6 units instead of reducing only one VO6 unit. In addition, MgVPO4O shows an energy barrier of about 0.58 eV for Mg-ion vacancy migration along the [111] direction, which is comparable to that of many other cathode materials. Our results indicated that MgVPO4O has the potential to be a promising candidate as a cathode material for Mg batteries.

Thermal, electrochemical and radiolytic stabilities of ionic liquids.

Research on ionic liquids has achieved rapid progress in the last several decades. Stability is a prerequisite for the application of ionic liquids. Ionic liquids may be used at elevated temperature, as electrolytes, or under irradiation. Therefore, the thermal, electrochemical, and radiolytic stabilities of ionic liquids are important and need to be known before their usage. Many research papers and some reviews on the stabilities of ionic liquids have been published. However, new results are continuously being published and a comprehensive review and perspective on this topic are still urgently needed. In this perspective, we intend to provide a comprehensive review including characterization methods, the effects of chemical composition of the ionic liquids on the thermal, electrochemical, and radiolytic stabilities of ionic liquids, respectively. Moreover, the thermal stability of some special types of ionic liquids such as poly(ionic liquids) and mixed ionic liquids, and the thermal and electrochemical stabilities of protic ionic liquids are discussed too. For thermal stability, the interactions between ions are less important than the individual anions and cations. The decomposition temperature is mainly determined by the less-stable ion, usually the anion. For electrochemical stability, the electrochemical window is determined by both the cation and anion. The less stable ion could influence the stability by interaction between the generated species from the decomposition with the more stable ion (opposite ion). This perspective is helpful for people to avoid using unstable ionic liquids and choose suitable ionic liquids.

Helical, Axial, and Central Chirality Combined in a Single Cage: Synthesis, Absolute Configuration, and Recognition Properties.

The synthesis of eight enantiopure molecular cages (four diastereomeric pairs of enantiomers) comprising a helically chiral cyclotriveratrylene (CTV) unit, three axially chiral binaphthol linkages, and three centrally asymmetric carbon atoms of a trialkanolamine core, is described. These new cages constitute a novel family of hemicryptophanes, which combine three classes of chirality. Their absolute configuration was successfully assigned by a chemical correlation method to overcome the signals overlap in the ECD spectra of the binaphtol and CTV units. Stereoselective recognition of glucose and mannose derivatives was investigated with these new chiral cages. Excellent enantio- and diastereoselectivity were reached, since in some cases, both exclusive enantio- and diastereo-discrimination have been observed. In addition, compared with the most relevant hemicryptophanes, these new cages also exhibit improved binding affinities.

Reaction mechanisms of carbon dioxide, ethylene oxide and amines catalyzed by ionic liquids BmimBr and BmimOAc: a DFT study.

The mechanisms of the one-pot conversion of carbon dioxide, ethylene oxide, and aniline to 3-phenyl-2-oxazolidionone catalyzed by the binary ionic liquids of BmimBr and BmimOAc were explored using the DFT methods. The complex reaction above comprises of two parallel reactions and a subsequent cascade reaction. DFT calculations on reaction pathways and energy profiles reveal that the electrostatic and hydrogen-bond effects of BmimBr play a crucial role in the parallel reactions for the generation of ethylene carbonate and 2-phenylamino-ethanol. Further, the subsequent cascade reaction to generate 3-phenyl-2-oxazolidinone catalyzed by BmimOAc follows a stepwise mechanism, which is more favorable than the concerted mechanism governed by BmimBr. In addition, BmimBr can accelerate the side reaction of aniline and ethylene oxide to yield a mixture of oligomers, which accords with the experimental observation. This theoretical work provides a deep insight into the catalytic roles of binary ionic liquids and also inspires us to design high efficient catalysts for the conversion of carbon dioxide further.

N-heterocyclic carbene formation induced fluorescent and colorimetric sensing of fluoride using perimidinium derivatives.

In this study, two perimidinium derivatives (1 and 2) were designed, synthesized, and developed as efficient fluorescent and colorimetric chemodosisensors for F(-) in DMSO or more competitive media (DMSO containing 10 % water). In the presence of F(-) , the yellow and non-fluorescent solution of 1/2 became colourless and exhibited strong blue fluorescence. This unique spectroscopic behaviour of 1/2 towards F(-) was attributed to the formation of N-heterocyclic carbene deprotonated by F(-) , which immediately reacted with water to give a colourless and fluorescent carbinol. Interestingly, it was found that this carbinol intermediate was unstable and further underwent a redox disproportionation to generate two other optically changed compounds. All the proposed mechanisms for the sensing process have been carefully confirmed by experiments.

Carbon black anchored vanadium oxide nanobelts and their post-sintering counterpart (V2O5 nanobelts) as high performance cathode materials for lithium ion batteries.

Carbon black (CB) anchored vanadium oxide (C-VOx) nanobelts are successfully prepared by a simple sol-gel route and subsequent hydrothermal treatment. The synthesized C-VOx nanobelts display high specific capacity and good cycling stability as a cathode material for lithium ion batteries (LIBs) (232 mA h g(-1) at initial discharge and 195 mA h g(-1) during 50th discharge at a current density of 100 mA g(-1) between 1.5-4 V versus Li) due to the nano-belted morphology and closely attached CB. The orthorhombic V2O5 nanobelts can be obtained by post-sintering of C-VOx nanobelts in air. These V2O5 nanobelts, which maintain their previous belted morphology and possess higher vanadium valence, exhibit superior electrochemical properties, especially the higher specific capacity (406 mA h g(-1) and 220 mA h g(-1) during the 1st and 50th discharge at a current density of 100 mA g(-1), and 146 mA h g(-1) at a current density of 1000 mA g(-1) between 1.5-4 V versus Li). Both of them can be used as high performance cathode materials for LIB application. Furthermore, a full-cell using V2O5 nanobelts as the cathode and lithiated graphite as the anode is assembled and its electrochemical performance is measured in the voltage range of 1.5-3.8 V.

Tavorite-FeSO4F as a potential cathode material for Mg ion batteries: a first principles calculation.

The electrochemical and Mg ion diffusion properties of tavorite-Mg0.5FeSO4F were studied by using first principles calculations. A discharge voltage of about 2.52 V versus Mg/Mg(2+) corresponding to the redox couples of Fe(3+)/Fe(2+) was predicted for tavorite-Mg0.5FeSO4F, and the experimental diffusion coefficient for the Mg-vacancy in Mg0.5-xFeSO4F is expected to be of the same order of magnitude as that of the Li-vacancy in Li1-xFeSO4F.

Acridine-based macrocyclic fluorescent sensors: self-assembly behavior characterized by crystal structures and a tunable bathochromic-shift in emission induced by H2PO4(-)via adjusting the ring size and rigidity.

In this paper, a series of novel acridine derived bisbenzimidazolium macrocyclic fluorescent sensors were designed and synthesized. X-ray crystal structures demonstrated the self-assembly behavior of these cyclophanes in the solid state driven by hydrogen bond and π-π interactions. Anion binding studies of these sensors revealed a significant effect of the macrocyclic size and rigidity for H2PO4(-) sensing via the obvious turn-on as well as bathochromic-shift in fluorescence emission. Different cavity size or rigidity of the sensors showed different bathochromic-shifts (from 36 to 126 nm) in fluorescence emission induced by H2PO4(-), which resulted in significant color changes of fluorescence from blue to orange red, orange, green and blue-green respectively. The unique fluorescence response toward H2PO4(-) may be attributed to H2PO4(-)-induced assembly of sensors forming the excimer between two acridine rings to a different extent.

Fabrication of Swellable Organic-Inorganic Hybrid Polymers for CO2-Assisted Hydration of Propylene Epoxide.

Swelling is a very common phenomenon in organic substances. However, the swelling behaviors of inorganic substances had rarely been reported. In this study, a new type of swellable organic-inorganic hybrid polymer (PIL@CHT) was designed and successfully synthesized through free-radical copolymerization of polymerizable phosphonium ionic liquid monomer and vinyl-functionalized hydrotalcite (CHT). The swelling behaviors of PIL@CHT in various solvents with a wide range of Hansen solubility parameters (δT) were investigated, and PIL@CHT exhibited excellent swellable capacity in the solvents with δT > 24.4 MPa1/2. The swollen state of the hybrid PIL@CHT in water presented a network structure with a diameter of approximately 8-12 µm, and CHT particles were well dispersed to the channel of PIL. PIL@CHT was applied to catalyze the CO2-assisted hydration of propylene oxide (PO), in which a cascade reaction including the cycloaddition of CO2 and PO and the subsequent hydrolysis of propylene carbonate (PC) occurred. PIL@CHT, combining the active sites of PIL and CHT, synergistically catalyzed this cascade reaction and achieved a high yield (93.0%) and selectivity (98.2%) of 1,2-propanediol (1,2-MPG) under a low H2O/PO ratio of 1.5/1. Moreover, the catalyst could be recycled seven times without any significant loss of catalytic activities and had good substrate generality.

Interlaminar Shear Characteristics of Typical Polyurethane Mixture Pavement.

Polyurethane (PU) can be used as a road material binder, and its mechanical properties, durability, temperature stability, and other road performance metrics are good. However, the interlayer bonding between PU mixtures and asphalt mixtures is poor. The influence of the pavement structure, interlayer treatment scheme, load, and environmental factors on the interlayer shear characteristics of PU mixture composite pavement is analysed. Further, dynamic modulus, Hamburg rutting, accelerated loading, and inclined shear tests were conducted, and the typical PU mixture pavement shear stress was calculated. The interlaminar shear stress of double layer PU mixture pavement, polyurethane-asphalt composite pavement, and typical asphalt pavement were calculated. The results showed that the PU mixture has a low rutting deformation rate, stable mechanical properties, and strong resistance to the coupled action of temperature, water, and loading. The double-layer PU mixture structure has good water-temperature stability and fatigue resistance; however, freeze-thaw and accelerated loading cause great damage to the double-layer PU mixture structure. The residual shear strength ratio after freeze-thaw cycles and accelerated loading is only 50.3% and 35.6%, respectively, while the influence on the double-layer asphalt mixture structure is less. The theoretical calculation results of different pavement structures show that when the temperature increases from 10 °C to 50 °C, the interlaminar shear stress of polyurethane-asphalt composite pavement increases by about 20%. Additionally, the shear stress of pavement PU mixture pavement and typical asphalt pavement is mainly affected by load, and the temperature changes have an obvious effect on the interlayer shear stress of polyurethane-asphalt composite pavement. The calculated maximum shear stress of the three pavement structures with different working conditions is less than the interlaminar shear strength measured by the inclined shear test, indicating that the interlaminar treatment scheme of composite specimens can meet the shear resistance requirements of the three typical pavement structure types.

Synthesis, Characterizations and Applications of Fluoroazaphosphatranes.

Haloazaphosphatranes are the halogenated parents of proazaphosphatranes, also known as Verkade's superbase. While the synthesis of iodo-, bromo- and chloroazaphosphatranes was reported more than thirty years ago by J. G. Verkade, the first synthesis of fluoroazaphosphatranes was only described in 2018 by Stephan et al. Currently, no common and versatile procedure exists to access fluoroazaphosphatranes platform with different structural characteristics. In this report, a new and simple synthesis of this class of compounds was developed based on the nucleophilic attack of the fluoride anion on chloroazaphosphatrane derivatives with good to high isolated yields for the corresponding fluoroazaphosphatranes (70-92%). The scope of the reaction was widened to fluoroazaphosphatranes bearing various substituents and X-ray molecular structures of two of them are reported. The stability of fluoroazaphosphatranes toward nucleophilic solvents like water has been investigated. As they revealed much more robust cations than their chloroazaphosphatrane parents, their chloride salts were tested as organocatalysts for the formation of cyclic carbonates from epoxides and CO2 . Fluoroazaphosphatranes proved to be both efficient and stable catalytic systems for CO2 conversion with catalytic activities similar to those of azaphosphatranes, and no decomposition of the cation was observed at the end of reaction.

Hybrid Lithographic Arbitrary Patterning of TiO2 Nanorod Arrays.

In this work, we report a hybrid lithographic method that combines the top-down soft lithography and the bottom-up hydrothermal approach for growing single-crystalline TiO2 nanorod arrays with arbitrary patterns. The arbitrary patterns of TiO2 seeds were obtained through the microcontact printing of the TiO2 seed precursor onto Si substrates using prepatterned poly(dimethylsiloxane) (PDMS) as stamps, followed by a baking process. Afterward, TiO2 nanorod arrays were selectively grown on patterned TiO2 seeds through conventional hydrothermal methods. By controlling the TiO2 seed precursor concentration, the hydrothermal reaction time and temperature and the patterns, the morphology and density of the TiO2 nanorods can be tuned in a controllable manner. Overall, this work provides a new strategy for the low-cost and facile preparation of patterned TiO2 nanorod arrays that has potential applications in micro-nano-optoelectronic devices and other fields.

Effects of Valence States of Working Cations on the Electrochemical Performance of Sodium Vanadate.

Supercapacitors have received much attention as large-scale energy storage devices for high power density and ultralong cycling life. In this work, sodium vanadate Na0.76V6O15/poly(3,4-ethylenedioxythiophene) (PEDOT) nanocables with deficient bridge oxygen at the interface (denoted Vo••-PNVO) have been tailored for supercapacitors through the in situ polymerization of 3,4-ethylenedioxythiophene and studied using three different electrolytes. Experiments and theoretical calculations reveal that all Na+, Zn2+, and Al3+ ions appear as hydrates in aqueous solutions but insert into the crystal structure as Na+ ions and Zn2+-H2O and Al3+-H2O hydrates, respectively. In comparison with the Zn2+-H2O and Al3+-H2O hydrates, Na+ ions with a smaller radius diffuse more quickly in Vo••-PNVO. Thus, Vo••-PNVO delivers better charge storage capability and stability when an electrolyte with Na+ ions is used. The results strongly suggest that an electrostatic interaction is significant in determining transport properties and storage capacities, rather than hydrate radii or valence states.

Unraveling the electronegativity-dominated intermediate adsorption on high-entropy alloy electrocatalysts.

High-entropy alloys have received considerable attention in the field of catalysis due to their exceptional properties. However, few studies hitherto focus on the origin of their outstanding performance and the accurate identification of active centers. Herein, we report a conceptual and experimental approach to overcome the limitations of single-element catalysts by designing a FeCoNiXRu (X: Cu, Cr, and Mn) High-entropy alloys system with various active sites that have different adsorption capacities for multiple intermediates. The electronegativity differences between mixed elements in HEA induce significant charge redistribution and create highly active Co and Ru sites with optimized energy barriers for simultaneously stabilizing OH* and H* intermediates, which greatly enhances the efficiency of water dissociation in alkaline conditions. This work provides an in-depth understanding of the interactions between specific active sites and intermediates, which opens up a fascinating direction for breaking scaling relation issues for multistep reactions.

1-(2-Ureidoeth-yl)quinolinium tetra-phenyl-borate.

In the cation of the title salt, C(12)H(14)N(3)O(+)·C(24)H(20)B(-), the dihedral angle between the quinoline ring and the mean plane of the urea fragment is 61.51 (5)°. In the crystal, the cations inter-act through weak C-H⋯O hydrogen bonding, forming a zigzag chain along the c-axis direction; the cations and anions are involved in weak inter-molecular C-H⋯π and N-H⋯π inter-actions as donors and acceptors, respectively.

New efficient ruthenium sensitizers with unsymmetrical indeno[1,2-b]thiophene or a fused dithiophene ligand for dye-sensitized solar cells.

Two novel ruthenium sensitizers containing unsymmetrical indeno[1,2-b]thiophene or a fused dithiophene unit in the ancillary ligand have been designed and synthesized. The photovoltaic performance of JK-188 using an electrolyte consisting of 0.6 M 1,2-dimethyl-3-propylimidazolium iodide, 0.05 M I(2), 0.1 M LiI, 0.05 M guanidinium thiocyanate, and 0.5 M tert-butylpyridine in acetonitrile revealed a short-circuit photocurrent density of 18.60 mA/cm(2), an open-circuit voltage of 0.72 V, and a fill factor of 0.71, yielding an overall conversion efficiency of 9.54%. The cell exhibits a remarkable stability under 1000 h of light soaking at 60 °C using a quasi-solid-state electrolyte consisting of 5 wt % poly(vinylidenefluoride-co-hexafluoropropylene), 0.6 M 1-propyl-2,3-dimethylimidazolium iodide, 0.5 M N-methylbenzimidazole, and 0.1 M I(2) in 3-methoxypropionitrile, retaining 97% of the initial efficiency (7.38%).