SANS study of hybrid silica aerogels under “in situ” uniaxial compression

We have modified the inorganic silica network of aerogels with polydimethylsiloxane (PDMS), a hydroxyl-terminated polymer, to obtain an organic modified silicate (ORMOSIL). Reactions were assisted by high-power ultrasounds. The resulting gels were dried under supercritical conditions of the solvent to obtain a monolithic sono-aerogel. The mechanical behaviour of these aerogels can be tuned from brittle to rubbery as a function of the organic polymer content. In order to determine the links between the mechanical behaviour and modifications made to the microstructure, SANS (small-angle neutron scattering) experiments were carried out. To measure the intensities under “in situ” uniaxial compression of the aerogel, a specific sample-holder was built. Under uniaxial compression the 2D-diagrams were significantly anisotropic (butterfly pattern), indicating the rearrangement of the polymer. The form factor of these aerogels is described well by two correlation lengths, small microporous silica clusters surrounded by entangled polymer chains of 6 nm average size (blobs), which form a larger secondary level of agglomerates governed by the “frozen-in” elastic constraints.     

In situ silica reinforcement of natural rubber by sol–gel process via rubber solution

The in situ silica filling of natural rubber (NR) was carried out via the sol–gel reaction using tetraethoxysilane. The effect of the in situ silica content on the curing, mechanical, dynamic mechanical and thermal properties of the composite vulcanizate materials was investigated in comparison to that with a commercial silica preparation. The Mooney viscosity of the in situ silica filled NR vulcanizates showed a lower value compared with that of the commercial filled ones. The mechanical properties of the in situ silica composite materials, i.e., the moduli and compression set, were improved compared with the commercial silica filler NR vulcanizates. The reinforcement effect of in situ silica did not accord with the Smallwood equation but in contrast was in good agreement with the Guth and Gold equation using a shape factor (f) which itself was in close agreement with estimates derived from independent TEM analysis. The pseudo-network structure of the in situ silica was low, which resulted in a lower storage modulus at 25 °C. By filling NR with in situ silica, the thermal properties of the composite vulcanized material were also improved, and well dispersed in situ silica particles within the NR matrix were also observed.     

In situ measurement of gas adsorption processes using Flux Response Technology

Flux Response Technology (FRT) is being developed as a powerful in situ perturbation technique to facilitate detailed characterisation of heterogeneous catalysts. FRT works by measuring minuscule changes in flowrate between two gas streams for potentially any gaseous process involving a change in volume (dV/dt). FRT functions analogous to an electrical Wheatstone bridge assembly whereby gas molecules represent electrons and flow capillaries represent resistors. A perturbation of pressure, temperature, but particularly of concentration causes an imbalance in the system, which is measured directly by a very sensitive differential pressure transducer (DPT). It is demonstrated how FRT can provide a simple, inexpensive, highly accurate means of quantifying the acidic sites of zeolites using ammonia ad/desorption as well as determining the dynamically available surface areas of catalysts using nitrogen adsorption at liquid nitrogen temperature. Temperature programmed experiments (temperature perturbations) can also be employed with FRT to rapidly compare catalyst activity directly (for catalyst development but also for quality control) without the need for much calibration.     

In situ silica reinforcement of methyl methacrylate grafted natural rubber by sol–gel process

In situ silica reinforcement of natural rubber (NR) grafted with methyl methacrylate (MMA) (MMA-GNR) was achieved via the sol–gel reaction of tetraethoxysilane (TEOS) by the use of solid rubber and latex solutions. Silica contents within the MMA-GNR as high as 48 and 19 phr were obtained when using the solid rubber and latex solutions, respectively, under optimum conditions. The conversion efficiency of TEOS to silica was close to 95%. The in situ formed silica MMA-GNR/NR composite vulcanizates were prepared. MMA-GNR/NR composite vulcanizates reinforced with the in situ formed silica prepared by either method had similar mechanical properties to each other, but a shorter cure time and higher mechanical properties than those reinforced with the commercial silica at 9 phr. The TEM micrographs confirmed that the in situ formed silica particles were well dispersed within the MMA-GNR/NR composite matrix, whilst the commercial silica particles showed a significant level of agglomeration and a lower level of dispersion.     

In situ infrared investigation of alkylation reaction of dianionic triruthenium ketenylidene cluster on magnesium oxide with methyl iodide

The reaction between [Ru_3(CO)_9(CCO)]~(2-) supported on magnesium oxide and alky-lating agent CH_3I was investigated in an attempt to understand its reactivity and mechanism byusing FT-IR technique. The IR spectra show that [Ru_3(CO)_9(CCO)]~(2-)/MgO reacts with CH_3Ito produce [Ru_3(CO)_9CC(O)CH_3]-/MgO, which exhibits bands at 2960, 2022, 1988, 1638, 1460and 1350 cm~(-1). The absorption at 2960, 1460 and 1350 cm~(-1) are attributed to -CH_3 group, whilebands at 2022, 1988 and 1952 cm~(-1) are assigned to the terminal CO groups attached to ruthenium.The band at 1638 cm~(-1) was assigned to acyl carbonyl. Isotopes labeled compounds CD3I, ~(13)COand [Ru_3(CO)_9(*C*CO)]~(2-) were used in investigation. The results demonstrate that β-carbon ofCCO ligand is attacked by CH_3~+ species and produces [Ru_3(CO)_9CC(O)CH_3]-/MgO.     

Preparation of cross-linked guar gum nanospheres containing tamoxifen citrate by single step emulsion in situ polymer cross-linking method

In the present work, guar gum nanospheres containing tamoxifen citrate (TC) were prepared and characterized for using it as a carrier for targeted drug delivery. Tamoxifen is a non steroidal drug used in the treatment of breast cancer. The compound administered to patients is the citrate salt of the trans isomer, tamoxifen citrate. Single step emulsion in situ polymer crosslinking technique was employed to prepare polymer coated drug nanoparticles. Model polymer used in this study was guar gum, which is commonly used for colon specific drug delivery in the pharmaceutical industry. During preparation four-different drug loading solvents were tried and dichloromethane provided the best drug loading result. Briefly, 5 mg drug was dissolved in dichloromethane and emulsified with an aqueous solution of guar gum using span 80 as emulsifier. Cross-linking was made by the use of cross linker glutaraldehyde during the process. A core shell type particles were observed. Drug load was confirmed by FT-IR and quantitated by HPLC. Nanoparticles were further characterized for particle size and morphology. Particle size between 200 and 300 nm were obtained. Influence of process variables on the size of nanoparticles were studied. It was observed that the concentration of polymer and stabilizer determined the size of nanoparticles.     

Synthesis, characterization and flame retardant of UV-curable hybrid coatings containing SiO2–P2O5–B2O3 via sol–gel method

A ternary sol containing silicon, phosphorus and boron modified by ??-methacryloxypropyltrimethoxysilane was synthesized by sol?Cgel method. The ternary sol was incorporated into the organic matrix and UV-curable organic/inorganic hybrid coating materials were obtained. Hardness, transmittance, haze, cross-cut adhesion and abrasion resistance results showed that the mechanical properties of the hybrid coatings improved effectively with no comprising on optical properties by increasing sol content. Scanning electron microscopy and Energy Dispersive X-ray spectrometer studies indicated that inorganic particles were homogenously dispersed in the organic matrix. The flame retardancy of the UV-curable coatings was investigated by thermogravimetric analysis and microscale combustion calorimeter. The results showed that the incorporation of sol into the organic network led to an improvement in the thermal stability and flame retardancy of the hybrid coating materials. It is a desirable achievement to improve simultaneously both flame retardancy and mechanical properties of the coatings.     

In situ fluorescence probing of the chemical and structural changes during formation of hexagonal phase cetyltrimethylammonium bromide and lamellar phase CTAB/Poly(dodecylmethacrylate) sol–gel silica thin films

Surfactant-templated mesostructured sol–gel films formed by evaporation induced self assembly (EISA) exhibit highly-ordered hexagonal, lamellar, and cubic structures. The steady-state dip-coating configuration allows both the chemistry and the dynamics of the EISA process to be traced in real time because the steps involved in the formation of the mesostructured material are separated both spatially and temporally in the dip-coating direction. The dynamic processes occurring during film formation can be conveniently monitored by the combination of interferometry and fluorescence spectroscopy of incorporated molecular probes. The selected probes respond to changes in their rotational mobility and the surrounding solvent composition and report these changes through their fluorescence characteristics. By taking in situ fluorescence spectra at various positions within the progressively thinning film, changes in the solvent composition, onset of micelle formation and further organization to the final mesophase structure can be followed. The luminescence of the probe molecule is measured with a spatial resolution of 100 μm. Two categories of surfactant-templated mesostructured sol–gel films were examined. Cetyltrimethylammonium bromide (CTAB) systems assemble into a 2-D hexagonal surfactant/silica mesophase with the surfactant concentration used in this study. CTAB dodecylmethacrylate systems assemble into a lamellar mesophase, which can be further polymerized to form a poly(dodecylmethacrylate)/silica hybrid nanocomposite that mimics nacre. X-ray diffraction patterns, transmission electron microscopy images, and other techniques are used to characterize the final films.     

Preparation of high performance nanocomposite elastomer: effect of reaction conditions on in situ silica generation of high content in natural rubber

Effect of amines on an in situ silica generation in natural rubber was investigated, and n-hexylamine, n-heptylamine and n-octylamine were found to increase the in situ silica content. The nanometer sized silica particles up to ca. 80 parts per hundred rubber by weight were generated in situ in the rubber matrix via a sol–gel reaction of tetraethoxysilane. Additionally, dispersion of the silica in the rubbery matrix was more homogeneous than that of commercial silica dispersed by a conventional mechanical mixing. In this in situ silica generation, the polarity and solubility in water of amine were influential factors for controlling the in situ silica content in the rubbery matrix. The obtained high in situ silica filled natural rubber was useful to prepare high performance nanocomposite elastomers.     

Poly(ethylene oxide)–poly(ethylene imine) block copolymers as templates and catalysts for the in situ formation of monodisperse silica nanospheres

Block copolymers based on poly(ethylene oxide) (PEO) and poly(ethylene imine) (PEI) are efficient catalysts/templates for the formation of uniform silica nanoparticles. Addition of tetraethylorthosilicate to a solution of PEO–PEI or PEI–PEO–PEI block copolymers results in the formation of silica particles with a diameter of ca. 30 nm and narrow size distribution. The particles precipitated with the diblock copolymers can be redispersed in water after isolation as individual nanoparticles. Evidently, block copolymers based on PEO and PEI serve as excellent templates for the biomimetic and “soft” synthesis of silica nanoparticles.

In situ analysis for spontaneous reduction of Eu<Superscript>3+</Superscript> in LiCl pyroprocessing media at 923 K

The spontaneous reduction of Eu³⁺ to Eu²⁺ was examined when EuCl₃ was added into a pyroprocessing media of LiCl molten salt at 923 K. The amount of Eu²⁺ was calculated by measuring the total charge consumed to oxidize Eu²⁺ ions to Eu³⁺ ions. The concentration ratio of Eu²⁺ to Eu³⁺ was estimated to be about 0.40 in the media. In addition, it is confirmed that the reduction of Eu³⁺ to Eu²⁺ is caused by the oxidation power of Cl⁻ to Cl₂. The coexistence of Eu³⁺ and Eu²⁺ in the LiCl molten salt system was examined by UV–Visible and luminescence spectroscopy. The molar absorptivities of Eu³⁺ and Eu²⁺, calculated from UV–Visible absorption spectra, were 423 and 1954 M⁻¹ cm⁻¹, respectively.     

In situ acetylation dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry for the simultaneous determination of musks,triclosan and methyl-triclosan in wastewaters

A rapid and environmental-friendly analytical method for the simultaneous analysis of different personal care products (PCPs) namely synthetic musks (nitro-, polycyclic and macrocyclic musks) and the disinfectant triclosan (TCS) and its transformation product methyl-TCS in wastewater samples has been developed. The method combines dispersive liquid–liquid microextraction with in situ aqueous derivatisation using acetic anhydride (Ac2O) prior to ?gas chromatography–mass spectrometry analysis. Several parameters affecting both extraction and derivatisation efficiency (e.g. type and volume of extractor and dispersive solvents, volume of derivatising reagent, etc.) were optimised to achieve reliable conditions. Validation of the method for all compounds under study showed good linearity with coefficient of correlation > 0.9947. Limits of quantification (LOQs) ranged between 2 and 72 ng/L for musks and 28 and 31 ng/L for TCS and methyl-TCS, respectively. Accuracy, expressed as the average recoveries, ranged between 76% and 87%, and precision, expressed in terms of intraday repeatability (%RSD), was better than 13% for all analytes. The application of the method to the analysis of 24 wastewater samples enabled the detection of all the target PCPs at concentration levels up to 2.7 μg/L, being galaxolide (HHCB) and tonalide (AHTN) the more prevalent, present in 88% and 46% of the samples, respectively.     

In situ scanning tunnelling microscopic study of the initial stages of growth and of the structure of the passive film on Ni(111) in 1 mM NaOH(aq)

In situ electrochemical scanning tunnelling microscopic (STM) measurements of the growth mechanism of the passive film on Ni(111) single-crystal surfaces in an alkaline 1 mM NaOH aqueous solution are reported. Stepping the potential from –1,050 mV/SHE, where the terrace topography of the bare Ni(111) surface is observed, to –800 mV generates a continuous step flow resulting from a slow dissolution of the surface localized at step edges of the surface. Islands are observed on the terraces that possibly correspond to the specific adsorption of hydroxide anions, without formation of an ordered structure. The nucleation of the passivating oxide is preferentially located at the step edges at this potential. The ongoing dissolution at the nearby step edges not yet passivated leads to the formation of isolated 2D islands of the passivating oxide. At –780 mV, the formation of extended islands constituted of 2D nanocrystals (~2 nm) is observed on the substrate terraces and blocks the dissolution at the step edges. The nanocrystals have an hexagonal lattice assigned to the formation of a monolayer of Ni(OH)₂(0001) in strained epitaxy on Ni(111). At E–630 mV, the formation of a facetted topography is observed as a result of the 3D growth of the passive film in tilted epitaxy on the substrate. Its structure is in excellent agreement with that expected for an unstrained 3D -Ni(OH)₂(0001) layer. This 3D layer of -Ni(OH)₂ is not reduced by a cathodic sweep of the potential down to –1,500 mV whereas the 2D islands are reduced under similar conditions. Ageing of the passive film shifts cathodically the potential of non-reversibility.Special issue for Prof. Gyorgy Horanyi on the occasion of his 70th birthday, in recognition of his outstanding contribution to Electrochemistry and Material Science.     

In situ sol–gel fabrication of new poly(amide–ether–imide)/titania (TiO<Subscript>2</Subscript>) nanocomposite thin films containing <Emphasis Type=SmallCaps>l</Emphasis>-leucine moieties

In this study, the synthesis, morphology, and thermal properties of amino acid containing polyimide/titania nanohybrid films are investigated. At first, a chiral diamine containing l-leucine moieties in the structure (synthesized previously) was polymerized with 4,4′-oxydiphthalic anhydride in extremely dry conditions. Resulted poly(amic acid) (PAA) was mixed with a moisture-sensitive titania precursor (tetraethyl orthotitanate [Ti(OEt)₄]) and casted to a dust-free glass plate. The water derived from thermal imidization of PAA hydrolyzed Ti(OEt)₄ to titania nanoparticles with almost spherical shapes. The thermogravimetric analysis of various nanocomposites confirms the improvement in the thermal stability with the increase in the percentage of titania nanoparticle. The transmission electron microscopy of nanohybrid films with 3%, 5%, and 10% w/w of titania contents confirms well dispersion of nanoparticles in the polymer ground. The X-ray diffraction spectra showed that the titania contents have amorphous structure.     

In situ electrochemical SFG/DFG study of CN⁻ and nitrile adsorption at au from 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl) amide ionic liquid([BMP][TFSA]) containing 4-{2-[1-(2-cyanoethyl)-1,2,3,4-tetrahydroquinolin-6-yl]diazenyl} benzonitrile (CTDB) and K[Au(CN)₂

In this paper we report an in situ electrochemical Sum-/Difference Frequency Generation (SFG/DFG) spectroscopy investigation of the adsorption of nitrile and CN? from the ionic liquid 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl) amide ([BMP][TFSA]) containing 4-{2-[1-(2-cyanoethyl)-1,2,3,4-tetrahydroquinolin-6-yl]-diazenyl}benzonitrile (CTDB) at Au electrodes in the absence and in the presence of the Au-electrodeposition process from K[Au(CN)?]. The adsorption of nitrile and its coadsorption with CN? resulting either from the cathodic decomposition of the dye or from ligand release from the Au(I) cyanocomplex yield potential-dependent single or double SFG bands in the range 2,125-2,140 cm?1, exhibiting Stark tuning values of ca. 3 and 1 cm?1 V?1 in the absence and presence of electrodeposition, respectively. The low Stark tuning found during electrodeposition correlates with the cathodic inhibiting effect of CTDB, giving rise to its levelling properties. The essential insensitivity of the other DFG parameters to the electrodeposition process is due to the growth of smooth Au.