Formation,structure and thermal properties of the ternary aggregate of polyethylene glycol, β-cyclodextrin and ferrocene

In this study, we firstly describe the formation of a ternary aggregate of ferrocene (Fc), polyethylene glycol (PEG) and β-cyclodextrin (β-CD). Our results provide strong evidence for the fact that the intermolecular aggregation behaviour leads to a striking change in structure and thermal property of the components aggregated. First of all, several independent experiments give us sufficient information about the structure of the aggregate: (1) the ternary aggregate tends to form a uniform fine-grained sponge structure, generating small particles with higher surface areas; (2) there is a threading mechanism of the PEG chain into the cavities of β-CD, and Fc plays the role of a stabiliser for such an aggregation; (3) there is a continual decrease in electron density of the Fe 2p3/2 region from free Fc to the binary aggregates of Fc and to the ternary aggregate. Next, the ternary aggregate exhibits a one-step degradation mechanism and has much lower thermal stability than free components and especially the physical mixture of the components. We believe that these findings are important and valuable for designing and fabricating polypseudorotaxanes, soft matters and organic/inorganic composite materials.     

Thermodynamics of the sorption of organic compounds on polyethylene glycol 400–permethylated β-cyclodextrin stationary phase and its enantioselectivity in gas chromatography

The thermodynamic characteristics of sorption of 24 organic compounds of various classes from the gas phase on the binary stationary phase based on polyethylene glycol 400 and permethylated β-cyclodextrin were determined. The influence of geometrical structure and optical activity of organic compounds on the possibility of forming sorbate–macrocycle complexes was examined. It was found that the studied stationary phase shows the enantioselectivity towards low-polar terpenes under the conditions of gas chromatography.     

Dynamic properties of the polyethylene glycol molecules on the oscillating solid–liquid interface

The dynamic properties of polyethylene glycol (PEG) molecules on the solid–liquid interface oscillating at MHz were investigated using the quartz crystal microbalance (QCM). The number-average molecular weights (M_n) of the PEG molecules were systematically varied over 4 orders of magnitude. This study makes it clear that the series-resonant frequency shift, ΔF, of the QCM against the square root of the density–viscosity product of the PEG solution is linear and has the intercept. Moreover, systematical analysis reveals that the ΔF slope rapidly decreases with M_n and that the ΔF intercept becomes constant above 4.0 × 10³ g mol⁻¹. As a result, those reveal that the resonant length of the PEG molecule moving with the oscillating plate of 9 MHz is 54.2 Å. We also find that the behaviors of ΔF due to M_n are mainly caused by the length of the PEG molecule.     

Study on the Synthesis of β-FeOOH by the Microemulsion Method

Monoclinic-FeOOH with: a = 0.9981 nm, b = 0.2948 nm, n = 1.0485 nm, β = 92.26° was synthesized by the hydrolysis of FeCl₃ · 6H₂O in micro emulsion including NP-4, octane, water. In this paper, the various morphology and size of the nano particles under different conditions are discussed, and it is found that the optimum conditions for synthesizing acicular β-FeOOH is that R = 6.0, [Fe³⁺] = 0.02 mol/L within the pH range 1.6–2.0. The text was submitted by the authors in English.     

Liquid chromatography of polyethylene glycol mono- and diesters: functional macromolecules or block copolymers?

The chromatographic behavior of polyoxyethylene-based polymers with adsorbing hydrophobic end-fragments was studied under two types of interaction conditions for the ethylene oxide (EO) component of such heteropolymers (which are either critical or of the size-exclusion type). In a theoretical part we assume a wide-pore situation, where the molecules are smaller than pores, and consider models of two-component diblock and triblock copolymers having quite strongly adsorbing blocks. A new step is made to extend a theory from difunctional macromolecules with point-type end-groups to triblock copolymers. It is shown that A-B-A triblocks with adsorbing A-blocks and with a "critical" B-block behave in chromatography like difunctionals with effective end-group interactions. Another important finding is the existence of a second critical region, which was observed on most of the studied columns. This region can be used to separate di- and triblocks from each other. Additionally, the individual oligomers of triblocks can be separated to the baseline. Complete separations of both diblocks and triblocks in one single chromatogram can be achieved by using a step gradient between two types of studied condtions.     

Gas-chromatographic studies of the sorption thermodynamics of adamantanes on a carbon adsorbent modified with polyethylene glycol with β-cyclodextrin additives

The thermodynamic characteristics of sorption of adamantane and its derivatives on a mixed stationary phase consisting of a graphite-like solid substrate, polyethylene glycol, and β-cyclodextrin (βCD) were determined by gas chromatography. The introduction of β-CD additives to a polar polymer matrix was shown to considerably decrease the chromatographic retention of the sorbates, which is evidence of the macrocyclic effect. The presence of β-CD molecules was found to increase the selective properties of the mixed sorbent with respect to the structural isomers of adamantanes.     

Use of polyethylene glycol in the process of sol–gel encapsulation of Burkholderia cepacia lipase

Lipases from Burkholderia cepacia were encapsulated using polyethylene glycol (PEG, M _w 1500) at various concentrations (0.5–3.0 %, w/v) as an additive during the sol–gel immobilisation process. Matrixes immobilized in the presence and absences of additives were characterized by thermal analysis [thermogravimetric (TG) and differential scanning calorimetry (DSC)], scanning electron microscopy (SEM), enzymatic activity, and total activity recovery yield (Ya). The addition of PEG increased the activity values, with Ya just above 1.0 % (w/v) in the presence of PEG. The additional of 1.0 % (w/v) PEG increased enzyme activity from 33.98 to 89.91 U g^?1 and the values of recovery yield were 43.0–91.4 %, compared to values of the samples without PEG. PEG enhanced the thermal stability of the matrix structure in the temperature range 50–200 °C, as confirmed by TG and DSC analyses. This was influenced by the presence of water bound to the matrix. The SEM micrographs clearly showed an increase in the number of deposits on the material surface, producing matrices with greater porosity.     

Synthesis of ZnO–SnO2 nanocomposites: impact of polyethylene glycol on morphological,luminescence and photocatalytic properties

Research on Chemical Intermediates - Zinc oxide-doped tin dioxide (ZnO–SnO2) nanomaterials were prepared by a sol–gel method with and without different amounts (0.5, 1.0 and...     

Synthesis of polyfunctional β-Ketosulfides and their reactions with m-chloroperbenzoic acid and chlorine dioxide

The reaction of bromoacetophenone with various thiols furnished β-ketosulfides: 2-(1-methyl-1H-imidazol-2-ylsulfanyl)-1-phenylethanone, 2-(1H-imidazol-2-ylsulfanyl)-1-phenylethanone, 2-(2-hydroxyethylsulfanyl)-1-phenylethanone. β-Ketosulfoxides were obtained by the oxidation of β-ketosulfi des with m-chloroperbenzoic acid and chlorine dioxide.     

Influence of the size and geometry of the anion binding pocket of sugar–urea anion receptors on chiral recognition

Three new chiral urea-type anion receptors were synthesized from aromatic diamines and 1-amino-1-deoxyglucose. The anion binding properties of these receptors were studied using chiral carboxylates derived from mandelic acid and three α-amino acids. We found that the size of the anion binding pocket played an important role in chiral recognition processes. The best results were obtained for 1,8-diaminoanthracene and α-amino acid anions.     

Proton-promoted dissolution of α-FeOOH nanorods and microrods: Size dependence, anion effects (carbonate and phosphate), aggregation and surface adsorption

Iron-containing oxide nanoparticles are of great interest from a number of technological perspectives and they are also present in the natural environment. Although recent evidence suggests that particle size plays an important role in the dissolution of metal oxides, a detailed fundamental understanding of the influence of particle size is just beginning to emerge. In the current study, we investigate whether nanoscale size-effects are observed for the dissolution of iron oxyhydroxide under different conditions. The dissolution of two particle sizes of goethite, α-FeOOH in the nanoscale and microscale size regimes (herein referred to as nanorods and microrods), in aqueous suspensions at pH 2 is investigated. It is shown here that in the presence of nitrate, nanorods shows greater dissolution on both a per mass and per surface area basis relative to microrods, in agreement with earlier studies. In the presence of carbonate and phosphate, however, dissolution of α-FeOOH nanorods at pH 2 is significantly inhibited, despite the fact that these anions result in a three- to fivefold enhancement of the dissolution of microrods relative to the nitrate anion. Light scattering techniques and electron microscopy show that nanorod suspensions are less stable compared to microrod suspensions resulting in nanorod aggregation under conditions where microrods stay more dispersed. Furthermore, spectroscopic studies using ATR-FTIR spectroscopy show distinct differences in phosphate and carbonate adsorption on nanorods compared to microrods. These results demonstrate that aggregation and the details of surface adsorption are important in the dissolution behavior of nanoscale materials.     

Modification of polyethylene films by radiation grafting of glycidyl methacrylate and immobilization of β-cyclodextrin

Glycidyl methacrylate was grafted onto polyethylene films using a preirradiation method with γ rays. The effect of absorbed dose, monomer concentration, and reaction time on the degree of grafting was determined. The grafted samples were verified by FTIR-ATR spectroscopy. β-Cyclodextrin was immobilized onto polypropylene modified with glycidyl methacrylate, and the ability of the cavities of β-cyclodextrin to form inclusion complexes was demonstrated using the typically organic compound approach with m-toluic acid (3-MBA) as a probe.     

Transition behaviors and hybrid nanofibers of poly(vinyl alcohol) and polyethylene glycol–POSS telechelic blends

We report solution properties of the blend solutions of poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG)–POSS telechelic and its corresponding hybrid nanofibers prepared by electrospinning. The morphologies, microstructures, and wettability of the resulting PVA/PEG3.4k–POSS hybrid nanofibers are studied. The morphologies of the resultant PVA/PEG3.4k–POSS nanofibers are regular with the fiber diameter ranging from 610 ± 110 to 810 ± 280 nm. When the content of PEG3.4k–POSS telechelic increases above 20 wt.%, the beaded fiber morphologies are observed due to severe aggregations of the PEG3.4k–POSS telechelics as well as increased viscosity at higher concentration. In addition, the solution properties of pure PEG3.4k–POSS telechelic solution (ca. 3–5 wt.%) and PVA/PEG3.4k–POSS solutions blended with PVA are explored, and found to show the reversible turbid-to-transparent transition behavior with respect to the solution temperature. Water contact angle measurement of the PVA/PEG3.4k–POSS nanofiber membranes demonstrates an enhanced hydrophobic nature due to the incorporated POSS moieties.     

First-Principles Investigation of β-FeOOH for Hydrogen Evolution: Identifying Reactive Sites and Boosting Surface Reactions

Akaganeite (β-FeOOH) is a widely investigated candidate for photo(electro)catalysis, such as water splitting. Nevertheless, insights into understanding the surface reaction between water and β-FeOOH, in particular, the hydrogen evolution reaction (HER), are still insufficient. Herein, a set of first-principles calculations on pristine β-FeOOH and halogen-substituted β-FeOOH are applied to evaluate the HER performance through the computational hydrogen electrode model. The results show that the HER on β-FeOOH tends to occur at Fe sites on the (010) surface, and palladium and nickel are found to serve as excellent co-catalysts to boost the HER process, due to the remarkably reduced free energy change of hydrogen adsorption upon loading on the surface of β-FeOOH, demonstrating great potential for efficient water splitting.     

Experimental and theoretical study of N-hexylcytosine and N-hexylcytosinium nitrate: the crucial role of hydrophobic and anion–π interactions

We report the synthesis and X-ray characterization of N¹-hexylcytosine (1) and N¹-hexylcytosinium nitrate (2). N¹-hexylcytosine (1) does not follow the same behaviour previously described for N¹-hexylthymine and N¹-hexyluracil in the solid state. This different behavior has been analyzed by means of density functional theory (DFT) calculations including the latest available correction for dispersion (D3). In addition hydrophobic and anion–π noncovalent interactions play a key role in stabilizing the 3D architectures of the compounds, which have been energetically studied using theoretical calculations and compared with similar structures retrieved from the Cambridge Structural Database (CSD). The anion–π–anion binding mode observed for nitrate in compound 2 is also observed in several crystal structures involving cytosine ring coordinated to transition metals.     

Effect of porosity on the kinetics of the two-route chlorine reaction: The chlorine evolution—ionization kinetics on iridium dioxide

The porosity effect on the kinetics of the chlorine reaction proceeding via two parallel paths is analyzed theoretically. An equation for the steady-state polarization curve is derived for these conditions. The chlorine evolution-ionization kinetics is studied by steady-state polarization measurements at a rotating disk electrode with an active iridium dioxide coating. A comparison of experimental and theoretical polarization curves shows the chlorine reaction to proceed via two parallel paths not only on DSA and RuO₂, but on IrO₂ as well     

Adsorption and corrosion inhibition behavior of polyethylene glycol on α-brass alloy in nitric acid solution

The corrosion performance of α-brass in 1 M HNO₃ and in the presence of polyethylene glycol (PEG) has been investigated using AC impedance spectra (EIS), potentiodynamic polarization (PP), electrochemical frequency modulation (EFM), and mass reduction (MR) techniques. The outcome data of EIS showed a rise in the resistance charge transfer (R_ct) and a decrease in the capacitance double layer (C_dl). Protection efficiency (IE) of PEG has been obtained by varying the dose of the PEG and temperature. PEG adsorbed on α-brass in acidic solution follows isotherm Langmuir. The polarization curves displayed that PEG acts as a mixed-kind inhibitor. The parameters obtained from thermodynamic activation of corrosion α-brass in 1 M HNO₃ were obtained and debated. The results obtained from all tests were in excellent agreement.     

The reactions of perfluorinated α- and β-alkoxyradicals with hydrogen chloride, chlorine and fluorine

The kinetics of the reactions of the macroradicals R_f′OCF₂ (I) and R_f′OCF₂CF₂ (II) with HCl, Cl₂ and F₂ have been studied in the liquid phase, being R_f′ a poly(oxydifluoromethylene-oxytetrafluoroethylene) chain with average molecular weight of about 10⁴ Da. Radical (I) showed a higher reactivity compared to radical (II) with all the three radical transfer agents.In case of HCl the activation energy for the reaction: