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Two anion receptors enhance liquid-liquid anion exchange when added to quaternary alkylammonium chloride anion exchangers, but with a striking dependence on the structure of the alkylammonium cation that suggests a supramolecular cooperative effect. Two anion receptors were investigated, meso-octamethylcalix[4]pyrrole (C4P) and the bisthiourea tweezer 1,1'-(propane-1,3-diyl)bis(3-(4-sec-butylphenyl)thiourea (BTU). Whereas synergism is comparatively weak when either methyltri(C8,10)alkylammonium chloride (Aliquat 336) or tetraheptylammonium chloride is used with the BTU receptor, synergism between C4P and Aliquat 336 is so pronounced that anion exchange prefers chloride over more extractable nitrate and trifluoroacetate, effectively overcoming the ubiquitous Hofmeister bias. A thermochemical analysis of synergistic anion exchange has been provided for the first time, resulting in the estimation of binding constants for C4P with the ion pairs of A336+ with Cl-, Br-, OAcF3-, NO3-, and I-. [ABSTRACT FROM AUTHOR]

We present an extensive study of a novel class of de novo designed tetrahedral M4L6 (M = Ni, Zn) cage receptors, wherein internal decoration of the cage cavities with urea anion-binding groups, via functionalization of the organic components L, led to selective encapsulation of tetrahedral oxoanions EO4n- (E = S, Se, Cr, Mo, W, n = 2; E = P, n = 3) from aqueous solutions, based on shape, size, and charge recognition. External functionalization with tBu groups led to enhanced solubility of the cages in aqueous methanol solutions, thereby allowing for their thorough characterization by multinuclear (1H, 13C, 77Se) and diffusion NMR spectroscopies. Additional experimental characterization by electrospray ionization mass spectrometry, UV-vis spectroscopy, and single-crystal X-ray diffraction, as well as theoretical calculations, led to a detailed understanding of the cage structures, self-assembly, and anion encapsulation. We found that the cage self-assembly is templated by EO4n- oxoanions (n ≥ 2), and upon removal of the templating anion the tetrahedral M4L6 cages rearrange into different coordination assemblies. The exchange selectivity among EO4n- oxoanions has been investigated with 77Se NMR spectroscopy using 77SeO42- as an anionic probe, which found the following selectivity trend: PO43- >> CrO42- > SO42- > SeO42- > MoO42- > WO42-. In addition to the complementarity and flexibility of the cage receptor, a combination of factors have been found to contribute to the observed anion selectivity, including the anions' charge, size, hydration, basicity, and hydrogen-bond acceptor abilities. [ABSTRACT FROM AUTHOR]

The combined extraction of cesium and strontium from caustic wastes can be achieved by adding a crown ether and a carboxylic acid to the Caustic-Side Solvent Extraction (CSSX) solvent. The ligand 4,4′(5′)-di(tert-butyl)cyclohexano-18- crown-6 and one of four different carboxylic acids were combined with the components of the CSSX solvent optimized for the extraction of cesium, allowing for the simultaneous extraction of cesium and strontium from alkaline nitrate media simulating alkaline high level wastes present at the U.S. Department of Energy Savannah River Site. Extraction and stripping experiments were conducted independently and exhibited adequate results tot mimicking waste simulant processing through batch contacts. The promising results of these batch tests showed that the system could reasonably be tested on actual waste. [ABSTRACT FROM AUTHOR]

The new cesium-selective macrocycle calix[4]arene-bis[4-(2-ethylhexyl) benzo-crown-6] (“BEHBCalixC6”) has been found to have improved solubility in a modified alkane diluent over calix[4]arene-bis(4-tert-octylbenzo-crown-6) (“BOBCalixC6”). The synthesis of this new calixcrown extractant, together with its solubility and extraction properties, is described in this report. The solubility, cesium extraction, and potassium loading behavior are compared with those of BOBCalixC6, the macrocycle currently employed in the caustic-side solvent extraction (CSSX) process for extracting cesium from alkaline nitrate solutions such as high-level nuclear waste. Replacement of the tert-octyl alkyl chains on the benzo-crown portion of the calixcrown by 2-ethylhexyl chains improves the equilibrium solubility of the free calixcrown in aliphatic diluents while not affecting the cesium extraction strength. Equilibrium concentrations of BEHBCalixC6 in Isopar L diluent modified with 0.5 M 1-(2,2,3,3-tetrafluoropropoxy)-3-(4-sec-butylphenoxy)-2-propanol (Cs-7SB) over the course of 41 weeks of gentle agitation at 25°C maintained the initial concentration of 57 ± 2 mM, with no evidence of precipitation or third-phase formation. In contrast, 57 ± 2 mM solutions of BOBCalixC6 prepared using sonication were not stable, with precipitation occurring to afford an equilibrium concentration of only 6.7 ± 0.2 mM after 41 weeks. Third-phase tests showed that BEHBCalixC6 resists third-phase formation as well as, or better than, BOBCalixC6. With increasing potassium loading from an alkaline sodium nitrate solution, both calixcrowns at 20 mM in modified Isopar L exhibited comparable onset of third-phase formation, gauging by the decreasing mass balance in cesium extraction from the same solutions. However, the BEHBCalixC6 solvent exhibited no visible indications of third-phase formation until the aqueous potassium concentration reached 0.75 M, whereas the BOBCalixC6 suffered visible third-phase formation when the aqueous potassium nitrate concentration reached 0.25 M. Calixcrowns with higher solubility in alkane diluents may find application in cesium extraction from waste matrices containing moderate (≥0.2 M) quantities of potassium, such as that stored at the US Department of Energy's Hanford Site, where higher concentrations of the calixcrown extractant may be required to obtain practical cesium distribution coefficients for process flowsheets. [ABSTRACT FROM AUTHOR]

A problem related to stripping efficiency has been identified in the use of crown ether derivatives to extract alkali metal salts, and a simple solution is proposed. Focusing on the specific case of cesium extraction from simulants of alkaline nuclear waste by a calix-crown ether, calix[4]arene-bis(tert-octylbenzo-crown-6) (BOBCalixC6), it has been shown that low concentrations of a common surfactant, dodecylsulfonate, seriously impairs stripping. This surfactant has been identified as a trace component in laboratory simulants and was subsequently studied in experiments in which it was added in controlled amounts. Computer modeling of stripping behavior is consistent with the formation of a 1:1:1 organic-phase complex of the calix-crown with cesium and its nitrate counterion. In the presence of an organophilic surfactant anion, cesium ion can only effectively be stripped from the solvent until its organic-phase concentration becomes equivalent to that of the surfactant anion. Cleanup of nuclear waste requires a high decontamination factor for 137Cs, and insufficient stripping therefore leads to process failure. This difficulty raises a generic issue for use of crown ethers for waste decontamination or for other hydrometallurgical applications. However, remediation is possible by simply adding an alkylamine to the solvent. The alkylamine in its ammonium form acts as a counterion of the organophilic anion, suppressing the deleterious effects of the organophilic anion and allowing the cesium cation to be stripped efficiently. Trioctylamine (TOA) at a concentration of only 1 mM was found effective at restoring stripping performance while not affecting extraction. Ultimately, this solvent amendment enabled the development of a robust solvent for the Caustic-Side Solvent Extraction (CSSX) process and its successful demonstration on actual nuclear waste. [Copyright &y& Elsevier]

Four calix[4]arene benzo-crown-6 ethers functionalized with primary amine groups in various positions have been synthesized. The cesium extraction behavior under alkaline and acidic conditions has been measured for these compounds and compared with that of non-amine containing analogs. Extraction strength when the amine group is neutral is not affected by the amino substituent, but protonation causes a marked decrease in extraction strength, permitting pH-switched back-extraction. [Copyright &y& Elsevier]

Investigates the effectiveness of alkylphenoxy fluorinated alcohols as modifiers in solvents for the extraction of cesium from alkaline nitrate media. Experimental details; Influence of the fluorinated portion of the modifier on chemical stability; Impact of the structure of the alkyl substituent of the alkylphenoxy moiety on the phase behavior of the solvent.

Examines the synergism and anion selectivity in sodium (Na) extraction by crown ether and weak lipophilic acids. Effect of ethers on strength of Na hydroxide separation from alkaline aqueous; Exchange reaction between the aqueous Na ion and ionizable proton of the organic acid; Mechanism of the ion-pair extraction of neutral sodium salts.

Describes a novel class of strong-base anion-exchange resins, bearing two different types of exchange sites. Pertechnetate sorption by commercial resins; Pertechnetate sorption by laboratory-prepared monofunctional resins; Pertechnetate sorption by bifunctional resins.

The effect of mutations of the catalytic dyad residues of SARS-CoV-2 main protease (MProWT) on the thermodynamics of binding of covalent inhibitors comprising nitrile [nirmatrelvir (NMV), NBH2], aldehyde (GC373), and ketone (BBH1) warheads to MPro is examined together with room temperature X-ray crystallography. When lacking the nucleophilic C145, NMV binding is -400-fold weaker corresponding to 3.5 kcal/mol and 13.3 °C decrease in free energy (ΔG) and thermal stability (Tm), respectively, relative to MProWT. The H41A mutation results in a 20-fold increase in the dissociation constant (Kd), and 1.7 kcal/mol and 1.4 °C decreases in ΔG and Tm, respectively. Increasing the pH from 7.2 to 8.2 enhances NMV binding to MProH41A, whereas no significant change is observed in binding to MProWT. Structures of the four inhibitor complexes with MPro1-304/C145A show that the active site geometries of the complexes are nearly identical to that of MProWT with the nucleophilic sulfur of C145 positioned to react with the nitrile or the carbonyl carbon. These results support a two-step mechanism for the formation of the covalent complex involving an initial non-covalent binding followed by a nucleophilic attack by the thiolate anion of C145 on the warhead carbon. Noncovalent inhibitor ensitrelvir (ESV) exhibits a binding affinity to MProWT that is similar to NMV but differs in its thermodynamic signature from NMV. The binding of ESV to MProC145A also results in a significant, but smaller, increase in Kd and decrease in ΔG and Tm, relative to NMV. [ABSTRACT FROM AUTHOR]

Whereas poly(3-alkyl-2,5-thiophene)s (P3AT), with many potential applications, have been extensively investigated, their ortho-connected isomers, poly(5-alkyl-2,3-thiophene)s (P5AT), have never been reported because of the difficulty in their syntheses. We herein present the first synthesis of regioregular P5AT via controlled Suzuki cross-coupling polymerization with PEPPSI-IPr as catalyst, affording the polymers with tunable molecular weight, narrow polydispersity (PDI), and well-defined functional end groups at the gram scale. The helical geometry of P5AT was studied by a combination of NMR, small-angle X-ray scattering (SAXS), and scanning tunneling microscopy (STM). Particularly, the single polymer chain of poly(5-butyl-2,3-thiophene) (P5BT) on highly oriented pyrolytic graphite (HOPG) substrates with either M or P helical conformation was directly observed by STM. The comparison of UV-vis absorption between poly(5-hexyl-2,3-thiophene) (P5HT) (λ = 345 nm) and poly(3-hexyl-2,5-thiophene) (P3HT) (λ = 450 nm) indicated that the degree of conjugation of the backbone in P5HT is less than in P3HT, which may be a consequence of the helical geometry of the former compared to the more planar geometry of the latter. Moreover, we found that P5HT can emit green fluorescence under UV (λ = 360 nm) irradiation. [ABSTRACT FROM AUTHOR]

A convenient and high-yield synthesis for N1-tritylethane-1,1,2,2- d4-1,2-diamine, a novel mono-protected ethylenediamine-C- d4, is reported. N1-tritylethane-1,1,2,2- d4-1,2-diamine was prepared in three steps from ethylene oxide- d4 in a combined yield in the range 68-76%. Also reported is a synthesis of ethylenediamine-C- d4 in two steps from 1,2-dibromoethane- d4 in a combined yield in the range 61-65%. [ABSTRACT FROM AUTHOR]

Abstract: A new class of task-specific ionic liquids (TSILs) based on the covalent attachment of imidazolium cations to a monoaza-crown ether fragment has been synthesized and characterized. The efficacy of these TSILs for the biphasic extraction of Cs+ and Sr2+ from aqueous solutions has been evaluated. The extraction properties of these TSILs can be influenced by the structures of the covalently attached imidazolium cations, which highlight the possibilities to enhance or tune the selectivities of crown ethers toward target ionic species through the covalent coupling with the imidazolium cations. [Copyright &y& Elsevier]

This work emphasizes the crucial role of polar solvating molecules known as phase modifiers in solvent-extraction systems. The focus of these studies was the extraction of cesium by calix[4tarene-bis(tert-octylbenzo-crown-6) in dodecane modified with various lipophilic alcohols. Results of equilibrium modeling are consistent with aggregation of the alcohol molecules with each other and with the calixarene-cesium nitrate complexes. These modeling results are supported by electrospray mass spectrometry experiments, clearly showing the alcohol:anion adducts containing several alcohol molecules. They are also supported by crystallographic evidence showing the existence of a hexameric aggregate in the solid state for a derivative of one of the alcohol modifiers used for solvent extraction, in agreement with the species giving the best modeling results. [ABSTRACT FROM AUTHOR]

So-called pseudo-hydroxide extraction has been proposed as a method for separating alkali metal hydroxide from alkaline salt solutions by use of weak-acid cation exchangers such as lipophilic phenols or fluorinated alcohols. Under extraction conditions, these lipophilic weak acids (HAs) are converted to their salt forms when dissolved in a suitable water-immiscible polar diluent like 1-octanol. Upon contact with water, the loaded solvents release alkali metal hydroxide to the aqueous phase by hydrolysis, thereby regenerating the extractant. This type of cycle has been demonstrated in previous work, wherein it was shown that bulk concentrations of .sodium hydroxide could be selectively separated from alkaline high-level waste simulants. In the present work, it has been the aim to identify the controlling equilibria and predominant species involved in the extraction process within the framework of a thermochemical model. Using 1 -octanol as the diluent, distribution ratios for sodium (DNa) extraction were measured as a function of organic-phase HA and aqueous-phase NaOH molarity at 25°C. The tested weak acids, 3,5-di-rfr/-butylphenoI (HA-I) and l-trifluoromethyl- 2-(3,5-di-/c;7-butylphenoxy) ethanol (HA-2). significantly enhanced the extraction of NaOH over the minor amount that is extracted by l-octanol alone. The extraction efficiency of HA-I was approximately 10-fold higher than that of HA-2. By use of the equilibrium modeling program SXLSQI. it was shown that a simple model is sufficient to quantitatively explain the observed extraction behavior based upon (a) ion-pair extraction to give Na+OH- ion pairs and corresponding free ions in 1-octanol and (b) cation exchange by monomeric HA molecules to form monomeric organic-phase Na+A- ion pairs and corresponding free organic-phase ions. [ABSTRACT FROM AUTHOR]

Results obtained in this work show that four calix[4]arene mono and bis(benzo-crown-6) ethers functionalized with primary amine groups feature markedly enhanced cesium stripping under acidic conditions compared with nonfunctionalized analogs. The four amine-derivatized calixarenes were surveyed in nitrobenzene diluent at 25°C, demonstrating the effect under controlled conditions, where it was seen that the amino functionalization entailed at most a mild sacrifice of cesium extraction strength or selectivity. Limited solubility of the protonated forms of the extractants appears to be a potential issue for future development, however. In the best case, calix[4]arene bis[4-(2-ethylhexyl)benzo-crown-6], possessing an aminomethyl group on the upper rim, (AMBEHB) exhibited a cesium extraction strength comparable to that of a control system containing calix[4]arene bis(tert-octylbenzo-crown-6) (BOB) under alkaline conditions, whereas stripping of the cesium from AMBEHB was 56-fold more effective than BOB. A proof-of-principle extraction, scrubbing, and stripping (ESS) cycle using AMBEHB in Isopar L modified with 0.75 M 1-(2,2,3,3-tetrafluoropropoxy)-3-(4-sec-butylphenoxy)-2-propanol (Cs-7SB) showed that a greater than three-fold more efficient stripping may be obtained with AMBEHB vs. its nonfunctionalized control BEHB. A slope analysis of systematic extraction data under caustic and acidic conditions confirmed that the extraction of cesium nitrate by AMBEHB in dodecane modified by 0.5 M Cs-7SB involves the formation of a 1:1:1 metal:ligand:nitrate organic species. [ABSTRACT FROM AUTHOR]

Solvent extraction of cesium ions from aqueous solution to hydrophobic ionic liquids without the introduction of an organophilic anion in the aqueous phase was demonstrated using calix[4]arene-bis(tert-octylbenzo-crown-6) (BOBCalixC6) as an extractant. The selectivity of this extraction process toward cesium ions and the use of a sacrificial cation exchanger (NaBPh4) to control loss of imidazolium cation to the aqueous solutions by ion exchange have been investigated. [ABSTRACT FROM AUTHOR]

A series of N-alkyl aza-18-crown-6 ethers were synthesized and characterized by NMR spectroscopy and mass spectrometry. These monoaza-substituted crown ethers in ionic liquids were investigated as recyclable extractants for separation of Sr2+ and Cs+ from aqueous solutions. The pH-sensitive complexation capability of these ligands allows for a facile stripping process to be developed so that both macrocyclic ligands and ionic liquids can be reused. The extraction efficiencies and selectivities of these monoaza-subslituted crown ethers for Na+, K+, Cs+, and Sr2+ were studied in comparison to those of dicyclohexano-18-crown-6 under the same conditions. The extraction selectivity order for dicyclohexano-18-crown-6 in the ionic liquids investigated here was K+ ≫ Sr2+ > Cs+ > Na+. The extraction selectivity order for N-alkyl aza-18-crown-6, in which the alkyl group is varied systematically from ethyl to n-dodecyl, was Sr2+ Gt; K+ > Cs+ > Na+ in 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide and 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfony1]amide and K+ > Sr2+ > Cs+ > Na+ in 1-hexyl-3-methylimidazolium bis[(trifluoromethyll)sulfonyl] amide and 1-octyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide. The strong dependence of selectivity on the type of ionic liquid indicates an important role played by solvation in solvent extraction processes based on ionic liquids. The optimization of macrocyclic ligands and ionic liquids led to an extraction system that is highly selective toward Sr2+. [ABSTRACT FROM AUTHOR]

Focuses on the selective separation of hydroxide from alkaline nuclear tank waste by liquid-liquid extraction with weak hydroxy acids. Prevention of pollution; Selectivity for hydroxide recovery; Description on repeated extraction and stripping cycles.

Magnesium batteries are promising candidates for beyond lithium-ion batteries, but face several challenges including the need for solid state materials capable of reversible Mg2+ insertion. Of fundamental interest is the need to understand and improve the Mg2+ insertion kinetics of oxide-based cathode materials in non-aqueous electrolytes. The addition of water in non-aqueous electrolytes has been shown to improve the kinetics of Mg2+ insertion, but the mechanism and the effect of water concentration are still under debate. We investigate the systematic addition of water into a non-aqueous Mg electrolyte and its effect on Mg2+ insertion into WO 3. We find that the addition of water leads to improvement in the Mg2+ insertion kinetics up to 6[H 2 O] : [Mg]2+. We utilize electrochemistry coupled to ex situ characterization to systematically explore four potential mechanisms for the electrochemical behavior: water co-insertion, proton (co)insertion, beneficial interphase formation, and water-enhanced surface diffusion. Based on these studies, we find that while proton co-insertion likely occurs, the dominant inserting species is Mg2+, and propose that the kinetic improvement upon water addition is due to enhanced surface diffusion of ions. • Water in a non-aqueous Mg electrolyte improves the ion insertion kinetics of WO 3. • We examined four possible hypotheses for the improved kinetics. • Proton co-insertion likely occurs but dominant inserting species is Mg2+. • We propose that water-enhanced surface diffusion could play a role. [ABSTRACT FROM AUTHOR]

We report a facile approach to control the shape memory effects and thermomechanical characteristics of a lignin-based multiphase polymer. Solvent fractionation of a syringylpropane-rich technical organosolv lignin resulted in selective lignin structures having excellent thermal stability coupled with high stiffness and melt-flow resistance. The fractionated lignins were reacted with rubber in melt-phase to form partially networked elastomer enabling selective programmability of the material shape either at 70 °C, a temperature that is high enough for rubbery matrix materials, or at an extremely high temperature, 150 °C. Utilizing appropriate functionalities in fractionated lignins, tunable shape fixity with high strain and stress recovery, particularly high-stress tolerance were maintained. Detailed studies of lignin structures and chemistries were correlated to molecular rigidity, morphology, and stress relaxation, as well as shape memory effects of the materials. The fractionation of lignin enabled enrichment of specific lignin properties for efficient shape memory effects that broaden the materials' application window. Electron microscopy, melt-rheology, dynamic mechanical analysis and ultra-small angle neutron scattering were conducted to establish morphology of acrylonitrile butadiene rubber (NBR)-lignin elastomers from solvent fractionated lignins. [ABSTRACT FROM AUTHOR]

Thermodynamic interaction and non-isothermal crystallization behavior in a series of protiated (H-) and deuterated (D-) poly(ε-caprolactone) (PCL) blends have been systematically investigated. The blends were thermodynamically miscible in the melt. The Flory−Huggins interaction parameter (χ) between H- and D-PCL segments was estimated. The hydroxyl groups in the PCL chain-ends were found to contribute significantly to the negative χ values. Combined characterization of small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) revealed that upon slow cooling, unique alternating H-rich and D-rich PCL lamellar structures are formed regardless of the blend ratio, which is attributed to the T c difference between H- and D-PCLs. While upon rapid cooling, mixed crystals of H- and D-PCLs are predominantly formed. These results provide insightful information on the melt thermodynamics as well as detailed chain arrangements in lamellar crystals for semi-crystalline H/D polyester blends. Image 1 • Thermodynamic interactions and crystallization behavior of protiated (H) and deuterated (D) PCL blends were investigated. • The hydroxyl groups in the PCL chain-ends were found to contribute significantly to the negative χ values. • Unique alternating H-rich and D-rich PCL lamellar structures are formed regardless of the blend ratio. [ABSTRACT FROM AUTHOR]

Deuterium labeling of semi‐crystalline polymers can dramatically affect their crystallization behaviors. However, the influence of different labeled positions in a partially deuterated polymer on its crystallization is still far from understood. Here, we synthesized a series of selectively deuterated poly(ε‐caprolactones) (PCLs) through ring‐opening polymerization of ε‐caprolactone with controlled deuteration sites, including fully protiated (D0), fully deuterated (D10), tetra deuteration at the 3‐ and 7‐ caprolactone ring positions (D4) and hexa deuteration at the 4‐, 5‐, and 6‐ caprolactone ring positions (D6). All the PCLs showed a similar lamellar structure and parameters. Differential scanning calorimetry (DSC) analysis revealed that the equilibrium melting temperature Tm0, melting temperature Tm, crystallization temperature Tc, and crystallization kinetics changed systemically with the deuterium content except for D4, which indicates that the presence of CD2 moieties on either side of ester group in the polymer chain combined with isotopic inhomogeneity could influence the chain packing. The nonmonotonic trend of Tm as a function of deuterium content could be attributed to the difference in a hydrogen‐bond like intermolecular interaction between different PCLs. Partially deuterated PCLs (D4 and D6) showed an Avrami index near 2. After analyzing the parameters at the same supercooling temperature ΔTc, the existence of two crystallization regimes of PCLs were detected. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 771–779 [ABSTRACT FROM AUTHOR]

The article presents a study on highly textured physical catalyst, composed of nitrogen-doped carbon nanospikes, for the electrolysis of nitrogen gas to ammonia. It mentions that the catalyst promotes electro reduction of dissolved nitrogen molecules near the electrode due to a surface composed of sharp spikes, which concentrates the electric field at the tips. It mentions importance of electrolyte as the reaction rate is dependent on the counter ion type.

Encapsulation behavior, as well as the presence of internal catalytically active sites, has been spurring the applications of a 3 nm hollow spherical metal oxide cluster {Mo132} as an encapsulation host and a nanoreactor. Due to its well-defined and tunable cluster structures, and nanoscaled internal void space comparable to the volumes of small molecules, this cluster provides a good model to study the dynamics of materials under nanoconfinement. Neutron scattering studies suggest that bulky internal ligands inside the cluster show slower and limited dynamics compared to their counterparts in the bulk state, revealing the rigid nature of the skeleton of the internal ligands. NMR studies indicate that the rigid internal ligands that partially cover the interfacial pore on the molybdenum oxide shells are able to block some large guest molecules from going inside the capsule cluster, which provides a convincing protocol for size-selective encapsulation and separation. [ABSTRACT FROM AUTHOR]

A typical type of core-shell polyoxometalates can be obtained through the Keggin-type polyoxometalate-templated growth of a layer of spherical shell structure of {Mo72Fe30}. Small-angle X-ray scattering is used to study the structural features and stability of the core-shell structures in aqueous solutions. Time-resolved small-angle X-ray scattering is applied to monitor the synthetic reactions, and a three-stage formation mechanism is proposed to describe the synthesis of the core-shell polyoxometalates based on the monitoring results. New protocols have been developed by fitting the X-ray data with custom physical models, which provide more convincing, objective, and completed data interpretation. Quasi-elastic and inelastic neutron scattering are used to probe the dynamics of water molecules in the core-shell structures, and two different types of water molecules, the confined and structured water, are observed. These water molecules play an important role in bridging core and shell structures and stabilizing the cluster structures. [ABSTRACT FROM AUTHOR]

Lithographic feature size requirements have approacheda few radiusof gyration of photoresist polymers used in thin-film patterning.Furthermore, the feature dimensions are commensurate with the photoaciddiffusion length that defines the underlying latent image. Smallerimaging building blocks may enable reduced feature sizes; however,resolution limits are also dependent upon the spatial extent of thephotoacid-catalyzed reaction diffusion front and subsequent dissolutionmechanism. The reaction-diffusion front was characterized by neutronreflectivity for ccc stereoisomer-purified, deuterium-labeled tert-butoxycarbonyloxy calix[4]resorcinarene molecular resists.The spatial extent of the reaction front exceeds the size of the molecularresist with an effective diffusion constant of (0.13 ± 0.06)nm2/s for reaction times longer than 60 s, with the maximumat shorter times. Comparison to a mean-field reaction-diffusion modelshows that a photoacid trapping process provides bounds to the spatialand extent of reaction via a reaction-limited mechanism whereas theratio of the reaction rate to trapping rate constants recovers theeffective diffusion peak. Under the ideal step-exposure conditions,surface roughness was observed after either positive- or negative-tonedevelopment. However, negative-tone development follows a surface-restructuringmechanism rather than etch-like dissolution in positive-tone development. [ABSTRACT FROM AUTHOR]

The ccc stereoisomer-purified tert-butoxycarbonyloxy-protected calix[4]resorcinarene molecular resists blended with photoacid generator exhibit a non-uniform photoacid-catalyzed reaction in thin films. The surface displays a reduced reaction extent, compared with the bulk, with average surface-layer thickness 7.0 ± 1.8 nm determined by neutron reflectivity with deuterium-labelled tert-butoxycarbonyloxy groups. Ambient impurities (amines and organic bases) are known to quench surface reactions and contribute, but grazing-incidence X-ray diffraction shows an additional effect that the protected molecular resists are preferentially oriented at the surface, whereas the bulk of the film displays diffuse scattering representative of amorphous packing. The surface deprotection reaction and presence of photoacid were quantified by near-edge X-ray absorption fine-structure measurements. The ccc stereoisomer-purified tert-butoxycarbonyloxy (t-Boc) protected calix[4]resorcinarene molecular resists for next-generation photolithography exhibit a non-uniform photoacid-catalyzed reaction in thin films. The surface displays a reduced reaction extent with preferential orientation, compared with the amorphous bulk. [ABSTRACT FROM AUTHOR]

Effective alternatives to nitric acid stripping in the Caustic-Side Solvent Extraction (CSSX) solvent have been demonstrated in this work. The CSSX solvent employs calix[4]arene-bis(tert-octylbenzo-18-crown-6) (BOBCalixC6) as the cesium extractant in a modified alkane diluent for decontamination of alkaline high-level wastes, such as those found at the Savannah River and Hanford sites. Results reported in this paper support the idea that replacement of the nitrate anion by a much more hydrophilic anion like borate can substantially lower cesium distribution ratios on stripping. Without any other change in the CSSX flowsheet, however, the use of a boric acid stripping solution in place of the 1 mM nitric acid solution used in the CSSX process marginally, though perhaps still usefully, improves stripping. The less-than-expected improvement was explained by the carryover of nitrate from scrubbing into stripping. Accordingly, more effective stripping is obtained after a scrub of the solvent with 0.1 M sodium hydroxide. Functional alternatives to boric acid include sodium bicarbonate or cesium hydroxide as strip solutions. Profound stripping improvement is achieved when trioctylamine, one of the components of the CSSX solvent, is replaced with a commercial guanidine reagent (LIX® 79). The more basic guanidine affords greater latitude in the selection of aqueous conditions in that it becomes protonated even at mildly alkaline pH values. Under process-relevant conditions, cesium distribution ratios on stripping are approximately 100-fold lower compared with the current CSSX performance. The tolerance to surfactants is good, and the extraction properties of the solvent remain unchanged over three successive extract-scrub-strip cycles. From the point of view of compatibility with downstream processing, boric acid represents an attractive stripping agent, as it is also a potentially ideal feed for borosilicate vitrification of the separated 137Cs product stream. The possibilities for use of these results toward a dramatically better next-generation CSSX process, possibly one employing the more soluble cesium extractant calix[4]arene-bis(2-ethylhexylbenzo-18-crown-6) (BEHBCalixC6) are discussed. [ABSTRACT FROM AUTHOR]

Investigates the ultrasensitive detection of CrO[sup 2-, sub 4] using a microcatilever sensor. Effect of SAM treatment time on the sensitivity; Cantilever deflection due to anion adsorption; Mechanics of the bending of microcantilevers.

• Deuterated chitosan was produced from the filamentous fungus Rhizopus oryzae. • All non-exchangeable hydrogens were substituted with deuterium except C2 by NMR. • SANS shows that deuteration does not change chitosan structure. • This is a new approach to produce deuterated chitosan for studies of biocomposites. Deuterated chitosan was produced from the filamentous fungus Rhizopus oryzae , cultivated with deuterated glucose in H 2 O medium, without the need for conventional chemical deacetylation. After extraction and purification, the chemical composition and structure were determined by Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and small-angle neutron scattering (SANS). 13C NMR experiments provided additional information about the position of the deuterons in the glucoseamine backbone. The NMR spectra indicated that the deuterium incorporation at the non-exchangeable hydrogen positions of the aminoglucopyranosyl ring in the C3 – C5 positions was at least 60–80 %. However, the C2 position was deuterated at a much lower level (6%). Also, SANS showed that the structure of deuterated chitosan was very similar compared to the non-deuterated counterpart. The most abundant radii of the protiated and deuterated chitosan fibers were 54 Å and 60 Å, respectively, but there is a broader distribution of fiber radii in the protiated chitosan sample. The highly deuterated, soluble fungal chitosan described here can be used as a model material for studying chitosan-enzyme complexes for future neutron scattering studies. Because the physical behavior of non-deuterated fungal chitosan mimicked that of shrimp shell chitosan, the methods presented here represent a new approach to producing a high quality deuterated non-animal-derived aminopolysaccharide for studying the structure-function association of biocomposite materials in drug delivery, tissue engineering and other bioactive chitosan-based composites. [ABSTRACT FROM AUTHOR]

Abstract: An efficient synthesis of 2,2,3,3,11,11,12,12-octamethyl-1,4,7,10,13-pentaoxacyclohexadecane (1, OM16C5) is described, which affords over an order of magnitude improvement in yield over the previously reported method. The first X-ray crystal structure of 1, as a complex with NaSCN, is also reported. [Copyright &y& Elsevier]

The chain arrangement within the crystalline lamellae has been the focus of polymer crystallization. In this study, a series of protiated (H) and deuterated (D) poly(ε-caprolactone) (PCL) blends, block and random copolymers were investigated by small-angle neutron scattering (SANS) measurements. The spatial inhomogeneities of block copolymers were analyzed via Debye-Bueche method and temperature dependence of Flory-Huggins interaction parameter χ in the melt was extracted from fitting the scattering data to the random phase approximation model. Studying the changes of SANS signals further revealed that the copolymers exhibit cooling rate-dependent crystallization behaviors. A unique SANS double-peak pattern was found in D4/D10 50/50 blend and D10-D0-D10 triblock copolymers (where D0, D4, and D10 indicate PCL with different levels of deuteration), as a result of two types of contrasts: scattering length density (SLD) difference between lamellae of different components and density difference between amorphous and lamellar domains. These detailed findings complement our understanding of the complex crystallization processes of deuterated polyesters, which also suggest an avenue for fine control of crystal structures that adds to materials design. Image 1 • Deuterated (D) PCL block and random copolymers were investigated by SANS measurements. • The spatial inhomogeneities of D-PCL triblock copolymers were calculated and χ parameters were extracted. • Bimodal SANS peaks were found in blends and triblock copolymers, which was resulted from two types of contrasts. [ABSTRACT FROM AUTHOR]

The nanoconfinement effect defined by the polyoxometalate nanocage renders the encapsulated bulky ligands rigid properties by significantly limiting and slowing down their diffusive motions. These ligands that partially cover the interfacial pore on the molybdenum oxide shells are able to block some large guest molecules from going inside the capsule cluster, which provides a convincing protocol for size‐selective encapsulation and separation. More information can be found in the Communication by P. Yin et al. on page 14131 ff. [ABSTRACT FROM AUTHOR]

Invited for the cover of this issue are Panchao Yin and collaborators at Oak Ridge National Laboratory. The image depicts a 2.9 nm molybdenum oxide molecular cluster for the size-selective encapsulation of small alkane molecules. Read the full text of the article at . [ABSTRACT FROM AUTHOR]