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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 (NaB[Ph.sub.4]) to control loss of imidazolium cation to the aqueous solutions by ion exchange have been investigated.

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 [Sr.sup.2+] and [Cs.sup.+] 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-substituted crown ethers for [Na.sup.+], [K.sup.+], [Cs.sup.+], and [Sr.sup.2]. 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.sup.+] >> [Sr.sup.2+] > [Cs.sup.+] > [Na.sup.+]. 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 [Sr.sup.2+] >> [K.sup.+] > [Cs.sup.+] > [Na.sup.+] in 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide and 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide and [K.sup.+] > [Sr.sup.2+] > [Cs.sup.+] > [Na.sup.+] in 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)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 [Sr.sub.2+].

The nature of the weak lipophilic acid used in synergistic combination with a model crown ether cation host was shown to have a strong effect on the strength and selectivity of sodium hydroxide separation from alkaline aqueous salt solutions. Sodium ion-pair extraction employing only cis--syn--cis-dicyclohexano--18-crown-6 (1) in nitrobenzene (NB) was correlated with the standard Gibbs energy ([DELTA][G.sub.p][degrees]) of anion partitioning into NB and was notably weak and nonselective for the hydroxide ion, in accord with Hofmeister bias. The Hofmeister order can be selectively overcome for NaOH by utilization of acid--base chemistry coupled with complexation of sodium ion in the NB phase. Upon addition of a lipophilic organic acid into the solution of 1 in NB, sodium extraction was selectively enhanced due to the initiation of an exchange reaction between the aqueous sodium ion and the ionizable proton of the organic acid. A series of weak lipophilic hydroxy acids (HA) including fluorinated alcohols and phenols was tested. The resulting synergistic pseudo-hydroxide extraction correlates with the p[K.sub.a] of the employed HA; the most acidic cation exchangers provide the greatest synergism. The synergistic factor obtained using a fluorinated benzyl alcohol 7 was as high as 256. Ion-pair extraction of neutral sodium salts was not changed or only mildly enhanced by addition of HA into the NB solution of 1. This enhancement was explained by hydrogen bonding of HA with the anion as related to the hardness of the anion and the acidity of HA. In comparison with the synergism observed for NaOH, this enhancement was weak and unable to overcome the Hofmeister effect. Examination of extraction selectivity revealed that the combination of 1 and 7 preferentially extracted NaOH over all other sodium salts, including the normally preferred nitrate and perchlorate salts. Quantitative recovery of NaOH from the NB phase was demonstrated via hydrolysis of the organic acid upon a single contact of the loaded solvent with water.

Researchers from Oak Ridge National Laboratory and the University of Tennessee conducted sorption experiments on pertechnetate using a class of bifunctional strong-base anion-exchange resin sites composed of two trialkyl-ammonium groups

Model distribution studies have demonstrated that the principle of synergistic pseudo-hydroxide extraction in which cation host molecules synergistically enhance liquid-liquid cation exchange of sodium ion by w weakly acidic hydrogen acid at high pH. This novel approach is based on the simultaneous utilizations of ion-exchange recovery and recycles in industrial applications.

Microcantilevers modified with a self-assembled monolayer respond sensitively to specific ion concentrations. Here, we report the detection of trace amounts of [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] using microcantilevers modified with a self-assembled monolayer of triethyl-12-mercaptododecylammonium bromide. The self-assembled monolayer was prepared on a silicon microcantilever coated with a thin layer of gold on one side. The microcantilever undergoes bending due to sorption of [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] ions on the monolayer-modified side. It was found that a concentration of [10.sup.-9] M [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] call be detected using this technology in a flow cell. Other anions, such as [Cl.sup.-], [Br.sup.-], [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII], and [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII], have minimal effect on the deflection of this cantilever. The mechanics of the bending and the chemistry of cantilever modification are discussed.

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]

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]

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.

We study responses of thermally annealed ultrathin films deposited on silicon substrates and containing polyzwitterions to applied electric fields by using specular neutron reflectometry (NR). In particular, we applied 7 kV under vacuum at 150 °C on the films containing poly(1-(3-sulfonatopropyl)-2-vinylpyridinium) (P2VPPS) and its blends with either a deuterated ionic liquid (EMIMBF 4 - d 11 ), potassium bromide (KBr), or deuterated sodium polystyrenesulfonate (NaPSS- d 7 ). The voltage was applied over an air gap, and the in situ neutron reflectivity measurements allowed us to measure changes in the films. In all the cases, we measured decreases in thicknesses of the films, which varied up to ∼8% depending on the added salt. Posteriori X-ray reflectivity (XRR) measurements on the same films at room temperature reveal that these films were highly hygroscopic, which led to the presence of water in these films. Analysis of the NR and the XRR revealed that the decrease in the thickness of the films in the neutron reflectivity experiments on heating resulted from the loss of water and the ionic liquid but not from electrostrictive effects. The in situ NR and posteriori XRR experiments revealed not only the hygroscopic nature of these films but also depth-resolved structural rearrangements due to the applied electric fields in the films containing electrolytes and polyelectrolytes. This work shows that a combination of NR and XRR can be used to distinguish between mass loss and electrostriction in films containing charged polymers such as polyzwitterions.

Converting lignin into well-defined compounds is often challenged by structural complexation and inorganic contamination induced by the pulping process. In this report, instead of breaking down lignin into small molecules, we extracted a uniform and rigid oligomer from the lignin waste stream. The multifunctional polyphenol oligomer containing carboxylic acid, alcohol, and phenol groups is highly reactive and brings stiffness into the material matrix. Tough and self-healing elastomers are economically prepared from this oligomer by a reaction with epoxy-terminated polyethylene glycol, without needing any solvent. Specifically, the polyaromatic backbone's rigidity enhances the elastomer's toughness, and the multiple polar substituents form a network of hydrogen bonding that heals the elastomer. Many other applications, including adhesives, hydrogels, coating, and metal scavengers, are envisioned based on this oligomer's unique properties.

Polyethylene terephthalate (PET) waste often contains a large amount of thermally unstable contaminants and additives that negatively impacts processing. A reduced processing temperature is desired. In this work, we report using a renewably sourced tall oil fatty acid (TOFA) as a modifier for recycled PET. To that end, PET was compounded with TOFA at different concentrations and extruded at 240 °C. Phase transition behaviors characterized by thermal and dynamic mechanical analyses exhibit shifts in the melting and recrystallization temperatures of PET to lower temperatures and depression of glass transition temperature from 91 to 65 °C. Addition of TOFA also creates crystal-phase imperfection that slows recrystallization, an important processing parameter. Changes in the morphology of plasticized PET reduces and stabilizes the melt viscosity at 240 and 250 °C. Melt-spun, undrawn continuous filaments of diameter 36-46 μm made from these low-melting PET exhibit 29-38 MPa tensile strength, 2.7-2.8 GPa tensile modulus, and 20-36% elongation. These results suggest a potential path for reusing waste PET as high-performance polymeric fibers., Competing Interests: The authors declare no competing financial interest.

Understanding the formation mechanism of giant molecular clusters is essential for rational design and synthesis of cluster-based nanomaterials with required morphologies and functionalities. Here, typical synthetic reactions of a 2.9 nm spherical molybdenum oxide cluster, {Mo132} (formula: [Mo(VI)72Mo(V)60O372(CH3COO)30(H2O)72](42-)), with systematically varied reaction parameters have been fully explored to determine the morphologies and concentration of products, reduction of metal centers, and chemical environments of the organic ligands. The growth of these clusters shows a typical sigmoid curve, suggesting a general multistep self-assembly mechanism for the formation of giant molecular clusters. The reaction starts with a lag phase period when partial Mo(VI) centers of molybdate precursors are reduced to form {Mo(V)2(acetate)} structures under the coordination effect of the acetate groups. Once the concentration of {Mo(V)2(acetate)} reaches a critical value, it triggers the co-assembly of Mo(V) and Mo(VI) species into the giant clusters.

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.

We present an extensive study of a novel class of de novo designed tetrahedral M(4)L(6) (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 EO(4)(n-) (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 ((1)H, (13)C, (77)Se) 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 EO(4)(n-) oxoanions (n ≥ 2), and upon removal of the templating anion the tetrahedral M(4)L(6) cages rearrange into different coordination assemblies. The exchange selectivity among EO(4)(n-) oxoanions has been investigated with (77)Se NMR spectroscopy using (77)SeO(4)(2-) as an anionic probe, which found the following selectivity trend: PO(4)(3-) ≫ CrO(4)(2-) > SO(4)(2-) > SeO(4)(2-) > MoO(4)(2-) > WO(4)(2-). 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.

Lithographic feature size requirements have approached a few radius of gyration of photoresist polymers used in thin-film patterning. Furthermore, the feature dimensions are commensurate with the photoacid diffusion length that defines the underlying latent image. Smaller imaging building blocks may enable reduced feature sizes; however, resolution limits are also dependent upon the spatial extent of the photoacid-catalyzed reaction diffusion front and subsequent dissolution mechanism. The reaction-diffusion front was characterized by neutron reflectivity 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 molecular resist with an effective diffusion constant of (0.13 ± 0.06) nm(2)/s for reaction times longer than 60 s, with the maximum at shorter times. Comparison to a mean-field reaction-diffusion model shows that a photoacid trapping process provides bounds to the spatial and extent of reaction via a reaction-limited mechanism whereas the ratio of the reaction rate to trapping rate constants recovers the effective diffusion peak. Under the ideal step-exposure conditions, surface roughness was observed after either positive- or negative-tone development. However, negative-tone development follows a surface-restructuring mechanism rather than etch-like dissolution in positive-tone development.