Hydration and dewetting near fluorinated superhydrophobic plates

The water dynamics near nanoscale fluorinated (CF(3)(CF(2))(7)(CH(2))(2)SiH(3)) monolayers (plates) as well as possible dewetting transitions in-between two such plates have been studied with molecular dynamics simulations in this paper. A "weak water depletion" is found near the single fluorinated surface, with an average water density in the first solvation shells 6-8% lower than its hydrogenated counterpart. The fluorinated molecules are also found to be water impermeable, consistent with experimental findings. More surprisingly, a dewetting transition is found in the interplate region with a critical distance D(c) of 10 A (3-4 water diameters) for double plates with 8 x 8 molecules each (plate size approximately 4 nm x 4 nm). This transition, although occurring on a microscopic length scale, is reminiscent of a first-order phase transition from liquid to vapor. The unusual superhydrophobicity of fluorocarbons is found to be related to their larger size (or surface area) as compared to hydrocarbons, which "dilutes" their physical interactions with water. The water-plate interaction profile shows that the fluorinated carbons have a 10-12% weaker water-plate interaction than their hydrogenated counterparts in the nearest solvation shell, even though the fluorocarbons do have a stronger electrostatic interaction with water due to their larger partial charges. However, the van der Waals interactions dominate the water-plate interaction within the nearest shell, with up to 90% contributions to the total interaction energy, and fluorocarbons have a noticeably weaker (by 10-15%) van der Waals interaction with water in the nearest shell than do hydrocarbons. Both the slightly weaker water-plate interaction and larger surface area contribute to the stronger dewetting transition in the current fluorinated carbon plates.     

On sub-T(g) dewetting of nanoconfined liquids and autophobic dewetting of crystallites

The glass transition temperature (T(g)) of thin films is reduced by nanoconfinement, but it is also influenced by the free surface and substrate interface. To gain more insights into their contributions, dewetting behaviors of n-pentane, 3-methylpentane, and toluene films are investigated on various substrates as functions of temperature and film thickness. It is found that monolayers of these molecules exhibit sub-T(g) dewetting on a perfluoro-alkyl modified Ni substrate, which is attributable to the evolution of a 2D liquid. The onset temperature of dewetting increases with film thickness because fluidity evolves via cooperative motion of many molecules; sub-T(g) dewetting is observed for films thinner than 5 monolayers. In contrast, monolayers wet substrates of graphite, silicon, and amorphous solid water until crystallization occurs. The crystallites exhibit autophobic dewetting on the substrate covered with a wetting monolayer. The presence of premelting layers is inferred from the fact that n-pentane crystallites disappear on amorphous solid water via intermixing. Thus, the properties of quasiliquid formed on the crystallite surface differ significantly from those of the 2D liquid formed before crystallization.     

Nonlinear evolution of thin liquid films dewetting near soft elastomeric layers

The nonlinear evolution of thin liquid films dewetting near soft elastomeric layers is examined in this work. Evolution equations are derived by applying the lubrication approximation and assuming that van der Waals forces in the liquid cause the dewetting and that the solid can be described as a linear viscoelastic material. Two cases are examined: (i) a liquid layer resting on an elastomer bounded from below by a rigid substrate, and (ii) an elastomer overlying a thin liquid film bounded from below by a rigid substrate. Linear stability analysis is carried out to obtain asymptotic relations which are then compared against solutions of the full characteristic equations. In the liquid-on-solid case, numerical solutions of the evolution equations show that van der Waals forces cause thinning of the liquid film and thickening of the elastomeric solid beneath film depressions. Inclusion of a short-range repulsive force suggests that regular patterns may form in which ridges of fluid rest on depressions in the solid. In the solid-on-liquid case, the van der Waals forces cause the solid layer to break up before the liquid film can dewet. The results presented here support the idea that the dewetting of thin liquid films might be exploited to create topographically patterned surfaces on soft polymeric solids.     

Hydration of tricalciumsilicate (Ca3SiO5) investigated by emanation thermal analysis

The method of emanation thermal analysis (ETA), based on the measurement of radon release from samples, has been used in the investigation of the tricalcium-silicate (Ca₃SiO₅) to characterize the microstructure development during the sample hydration. Results of the ETA made it possible to obtain the diffusion structural diagnostics of the material under in situ conditions of it is hydration. The influence of temperature and surface area of the tricalcium-silicate sample on kinetics of the sample hydration was characterized. Computer modeling of time dependences of radon release rate during hydration of tricalcium-silicate was carried out. A good agreement of the numerical model with the experimental results of the radon release was found.     

硫酸高铈催化炔烃的水合反应研究

炔烃经水合反应生成酮是有机合成中最重要和最基本的进行官能团转换的方法之一. 我们提供了一种价廉且具有高选择性的硫酸高铈催化炔烃水合方法. 实验结果表明: 在硫酸高铈(0.1 mmol)、浓硫酸(0.06 mL)、水(0.02 mL)和苯(5 mL)且反应温度为70 ℃的反应条件下, 炔烃(1 mmol)可以顺利发生水合反应生成酮.     

Hydration and dissociation of hydrogen fluoric acid (HF)

The hydration and dissociation phenomena of HF(H(2)O)(n)() (n < or = 10) clusters have been studied by using both the density functional theory with the 6-311++G[sp] basis set and the M?ller-Plesset second-order perturbation theory with the aug-cc-pVDZ+(2s2p/2s) basis set. The structures for n > or = 8 are first reported here. The dissociated form of the hydrogen-fluoric acid in HF(H(2)O)(n) clusters is found to be less stable at 0 K than the undissociated form until n = 10. HF may not be dissociated at 0 K solely by water molecules because the HF H bond is stronger than the OH H bond, against the expectation that the dissociated HF(H(2)O)(n) would be more stable than the undissociated one in the presence of a number of water molecules. The dissociation would be possible for only a fraction of a number of hydrated HF clusters by the Boltzmann distribution at finite temperatures. This is in sharp contrast to other hydrogen halide acids (HCl, HBr, HI) showing the dissociation phenomena at 0 K for n > or = 4. The IR spectra of dissociated and undissociated structures of HF(H(2)O)(n) are compared. The structures and binding energies of HF(H(2)O)(n) are found to be similar to those of (H(2)O)(n+1). It is interesting that HF(H(2)O)(n=5,6,10) are slightly less stable compared with other sizes of clusters, just like the fact that (H(2)O)(n=6,7,11) are slightly less stable. The present study would be useful for the experimental/spectroscopic investigation of not only the dissociation phenomena of HF but also the similarity of the HF-water clusters to the water clusters.     

Stimuli responsive poly(1-[11-acryloylundecyl]-3-methyl-imidazolium bromide): dewetting and nanoparticle condensation phenomena

A stimuli-responsive homopolymer poly(ILBr) is fabricated via a "two-phase" atom transfer radical polymerization (ATRP) process, where ILBr stands for the reactive ionic liquid surfactant, 1-[11-acryloylundecyl]-3-methyl-imidazolium bromide. An extraordinarily wide molecular weight distribution (PDI = 6.0) was obtained by introducing the initiator (4-bromomethyl methyl benzoate) in a heterogeneous two-phase process. The molecular weight distribution of poly(ILBr) was characterized by size-exclusion chromatography (SEC). The resulting homopolymer was found to be surface active and stimuli responsive. Poly(ILBr) films coated on quartz exhibit stimuli-responsive dewetting after ion exchange of Br(-) by PF(6)(-). This dewetting phenomenon can be understood in chain segmental terms as a stimuli-induced structural relaxation and appears to be the first such reported stimuli-responsive polymeric dewetting. Titrating aqueous poly(ILBr) with aqueous bis(2-ethylhexyl)sulfosuccinate induces nanophase separation and results in the condensation of nanoparticles 30-60 nm in diameter.     

Hydration Dynamics of Water near an Amphiphilic Model Peptide at Low Hydration Levels: A Dielectric Relaxation Study

A dielectric relaxation study of aqueous solutions of the amphiphilic model peptide N‐acetyl‐leucine amide (NALA) at 298 K over a wide range of hydration levels is presented. The experiments range from states where water builds up several hydration layers to states where single water molecules or small water clusters are shared by several NALA molecules. The dielectric spectra reveal two modes on the 10 and 100 ps timescales. These are largely broadened with regard to the Lorentzian shape caused by simple Debye‐type relaxation, and are well described by the Kohlrausch–Williams–Watts stretched exponential function. The fast mode is assigned to water reorientation comprising bulk water as well as hydration water. Even when all water molecules are in contact with the solute, this fast component is dominant, and its mean relaxation time is retarded by less than a factor of two relative to neat water. The amplitude of the slow process is far higher than expected for the dipolar reorientation of the solute. The observations are consistent with results from molecular dynamics simulations for a similar model peptide reported in the literature. They suggest that the slow relaxation mode is mainly founded in peptide–water dipolar couplings, with some additional contribution from slowly reorienting hydration water molecules. The results are discussed with regard to the hydration dynamics of proteins and the interpretation of dielectric spectra of protein solutions.     

Hydration of copper(II) amino acids complexes

Hydration of the copper(II) bis‐complexes with glycine, serine, lysine, and aspartic acid was studied by DFT and MD simulation methods. The distances between copper(II) and water molecules in the 1st and 2nd coordination shells, the average number of water molecules and their mean residence times in the hydration shells were calculated. Good agreement was observed between the values obtained and those found by DFT and NMR relaxation methods. Influence of the functional groups of the ligands and the cis–trans isomerism of the complexes on the structural and dynamical parameters of the hydration shells was displayed and explained. Analysis of the MD trajectories reveals the competition for a copper(II) axial position between water molecules or water molecules and the functional chain groups of the ligands and confirms the suggestion on the pentacoordination of copper(II) in such complexes. MD simulations show that only one axial position of Cu(II) is basically occupied at each time step while in average the coordination number more than 5 is observed. © 2017 Wiley Periodicals, Inc.     

Hydration properties of aqueous Pb(II) ion

Using density functional theory and polarized continuum models, we have determined the most probable coordination number and structure of the first hydration shell of aqueous Pb(II). The geometries and hydration free energies of Pb(H2O)(1-9)(2+) were examined and benchmarked against experimental values. The free energies of hydration of Pb(H2O)(6-8)(2+) were found to match the experimental value within 10 kcal/mol. Moreover, based upon our thermochemical results for single water addition, primary hydration numbers of 6, 7, and 8 are all thermally accessible at STP. Use of a small-core 60 electron effective core potential (ECP) with the aug-cc-pvdz-PP basis on Pb resulted in structures that are significantly less hemidirected than predicted when using the large-core 78 electron ECP and the lanl2DZ basis on the metal. Our results imply that the hemi- to holo-directed transition in Pb(II)-water complexes is driven by coordination number and not hybridization of the 6s lone-pair orbital or enhanced covalent bonding in the Pb-OH2 bond. In addition to basis set effects, the influence of different solvation models on hydration reactions has further been examined so as to determine the relative accuracy of the calculated hydration thermochemistry.     

Pattern formation in dewetting poly(tert-butyl acrylate)/polyhedral oligomeric silsesquioxane (POSS) bilayer films

The surface morphology of dewetting poly(tert-butyl acrylate) (PtBA) and trisilanolphenyl-POSS (TPP) bilayers has been studied as a function of time at 95 degrees C. For short annealing times, only the upper nanoparticle (TPP) layer dewets from the underlying PtBA layer. The number and lateral dimensions of the holes in the upper TPP layer increase with increasing annealing times, forming interconnected rim structures. At later annealing times, scattered holes that reach down into the PtBA layer are observed among the interconnected rim structures. Fractal nanofiller (TPP)-rich aggregates are found at the bottom of the scattered holes.     

Solvent-driven dewetting and rim instability

An experimental method suitable for reproducible results has been used to investigate dewetting behavior of thin films of solvent-laden polymer. This solvent-driven dewetting enables one to change spreading coefficient by an order of magnitude that is not readily realizable in thermal dewetting and to study polar interactions that have not been fully exploited experimentally. While the film instability is similar to that found in thermal dewetting, the rim instability is quite different. Two different types of the rim instability have been found. With a polar solvent, the rim instability changes from one type to another with increasing film thickness whereas the unstable rim becomes stable for an apolar solvent.     

Hydration of Lanthanoids(III) and Actinoids(III): An Experimental/Theoretical Saga

The latest experimental and theoretical studies on structural and dynamical properties of lanthanoid(III) and actinoid(III) ions in water have been reviewed. In the last years, most of the issues about lanthanoid(III) hydration have been resolved combining X-ray absorption experiments and different theoretical methods. Since 2008 an effort has been made to treat the entire series thus obtaining coherent sets of experimental and theoretical results that were lately put together in such a way that it was possible to derive new basic properties, such as effective ionic radii, across the series. While for the hydration of lanthanoids(III) many experiments and simulations have been reported, the hydration of actinoids(III) was less investigated. There are some experiments performed by different research groups and few simulations that we discuss in this review. Currently, there are enough results that it is possible to gain some understanding of the hydration behavior of lanthanoids(III) and actinoids(III). The ultimate goal of this review is to provide clues on the analogies and differences between the two series. These aspects are connected to several issues: 1)?technological: the separation of these elements that is necessary for recycling and stocking of nuclear waste, 2)?practical: because experiments on actinoids need particular care, the definition of possible analogies will give the possibility to use the correct lanthanoid when the information on a specific actinoid is needed, 3)?fundamental: related to chemical similarities between the two series.     

Ion Association and Hydration in Aqueous Solutions of Nickel(II) and Cobalt(II) Sulfate

Aqueous solutions of nickel(II) and cobalt(II) sulfate have been investigated at 25 ^∘C by dielectric relaxation spectroscopy (DRS) over a wide range of frequencies (0.2 ≤ ν (GHz) ≤ 89) and salt concentrations (0.025 ≤ c(mol-L⁻¹) ≤ 1.4). The spectra indicate, as for MgSO₄(aq) studied previously, the simultaneous presence of double solvent-separated, solvent-shared and contact ion pairs in both NiSO₄(aq) and CoSO₄(aq). The stepwise formation constants for each ion-pair type and the overall association constant, obtained from the data are in good agreement with ultrasonic relaxation and other estimates. The DR spectra at higher concentrations (c ≥ 0.5 mol-L⁻¹) suggest the existence of a nonlinear triple ion M₂SO₄²⁺(aq). Consistent with the very strong hydration of the salts, which have ‘effective’ hydration numbers approaching 27 at infinite dilution, there are no significant differences in any of the relaxation or thermodynamic parameters for NiSO₄(aq) and CoSO₄(aq), except that the triple ion appears to be somewhat more stable for the latter.     

Efficient Mo(VI)-Catalyzed Hydration of Nitrile with Acetaldoxime

A method for the selective hydration of nitrile to amide by employing commercially available acetaldoxime and inexpensive oxometallate such as molybdate, vanadate, and tungstate in environmentally friendly water is described. Under this protocol, nitriles including aromatic nitriles, heterocyclic nitriles, and aliphatic nitriles were converted into the corresponding amides in good to excellent yields.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Hydration and oxidation kinetics of a proton conductor oxide, SrCe(0.95)Yb(0.05)O(2.975)

The oxidation and hydration kinetics of a proton conductor oxide, SrCe(0.95)Yb(0.05)O(2.975), were examined via conductivity relaxation upon a sudden change of oxygen activity in a fixed water-activity atmosphere, and vice versa, in the ranges of -4.0 < log a(O(2)) < or = 0.01 and -5.0 < log a(H(2)O) < -2.0 at 800 degrees C. It was found that under an oxygen-activity gradient in a fixed water-vapor-activity atmosphere, the conductivity relaxation with time is monotonic with a single relaxation time (as usual), yielding a chemical diffusivity that is unequivocally that of the component oxygen. In a water-activity gradient in a fixed oxygen activity atmosphere, on the other hand, the conductivity relaxation appears quite unusual, exhibiting an extremum after an initial transient. The conductivity relaxation upon hydration or oxidation, in general, is quantitatively analyzed in terms of two apparent chemical diffusivities for component oxygen and hydrogen, respectively. The inner workings of hydration is discussed, and the as-evaluated chemical diffusivities are reported and compared with the conventional chemical diffusivity of water.