Synthesis of water-soluble homo- and block-copolymers by RAFT polymerization under γ-irradiation in aqueous media

The ambient temperature (20 °C) reversible addition fragmentation chain transfer (RAFT) polymerization of several water-soluble monomers conducted directly in aqueous media under γ-initiation (at dose rates of 30 Gy h⁻¹) proceeds in a controlled fashion. Using functional trithiocarbonates, i.e., S,S-bis(α,α′-dimethyl-α″-acetic acid) trithiocarbonate (TRITT), 3-benzylsulfanyl thiocarbonylsulfanyl propionic acid (BPATT), and dithioester, i.e., 4-cyanopentanoic acid dithiobenzoate (CPADB), as chain transfer agents, fully water-soluble polymers of monomers such as N,N-dimethylacrylamide, 2-hydroxyethyl acrylate, acrylamide or oligo(ethylene glycol) methacrylate and stimuli-responsive polymers of monomers such as acrylic acid, N-isopropylacrylamide, 2-(dimethylamino)ethyl methacrylate or 2-acrylamido-2-methylpropane sulfonic acid can be obtained over a wide range of degrees of polymerization up to 10,000 with low polydispersity (typically ) to near quantitative conversions. Well-defined block copolymers between these monomers, based on several asymmetric macro-RAFT agents, can be obtained, suggesting that the RAFT agents are stable throughout the polymerization process so that complex and well-defined architectures can be obtained.     

Electrochemical investigation of the diffusion of lithium in β-LiAl alloy at room temperature

The chemical diffusion coefficients of lithium in -LiAl alloy were measured by the use of transient techniques such as chronopotentiometry, chronoamperometry and a.c. impedance spectroscopy in 1 M LiClO₄-propylene carbonate at 25° C. A -LiAl layer, formed by electrodepositing lithium on a thin aluminium substrate having a microstructure of preferred (100) orientation, was mainly used. The values of the diffusion coefficients were found to be of the order of 10^–10 cm²s^–1, which are close to those reported in the literature. A scatter in the coefficient was discussed in terms of the formation and disruption of the passivating layer on the alloy.     

Elastic properties and damping behavior of alumina–zirconia composites at room temperature

Alumina–zirconia composite ceramics (AZ composites) have been prepared in the whole range of compositions from pure alumina to zirconia (in steps of 10 vol.%) by slip casting, followed by sintering at 1350 °C and microstructural characterization via the Archimedes method (relative densities 0.93–0.99). Young's modulus has been measured at room temperature via the impulse excitation technique (IET) and, after appropriate porosity correction (linear, power-law, exponential), found to be in good agreement with the Hashin–Shtrikman bounds. The damping factor (internal friction), which has been measured for dense AZ composites (also via IET at room temperature), is found to increase with increasing zirconia content. Damping factors measured for porous AZ composites with porosities 25–71%, prepared with corn starch as a pore former, have been found to depend only slightly on porosity, unless the porosities are extremely high (>70%). At these porosities, however, where the Young's moduli approach zero, the damping factors exhibit a steep increase.     

Ring-opening polymerization of γ-glycidoxypropyltrimethoxysilane catalyzed by multi-metal cyanide catalyst

Ring-opening polymerizations of γ-glycidoxypropyltrimethoxysilane (GPTMS) were carried out by using multi-metal cyanide (MMC) catalyst and the synthesized homopolymer was a comb-shaped polymer with regular structure. The structure of the polymer obtained (P-GPTMS) was characterized by FTIR, ¹H-NMR, and ²⁹Si-NMR spectroscopy, and the molecular weight and its distribution were analyzed by size-exclusion chromatography with multi-angle laser light scattering (SEC-MALLS). The thermal behavior of P-GPTMS was investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). P-GPTMS with high molecular weight (M _n = 18,000–80,000) and narrow molecular weight distribution (1.10–1.35) were synthesized when the dosage of MMC catalyst was 0.1% and polymerization temperature was 130 °C. The molecular weight of the product could be adjusted by controlling the polymerization time. The T _g of P-GPTMS is in the range of −34 to −30 °C. On the basis of the TGA data, the decomposition rate of P-GPTMS reached its peak at 374.14 °C and the entire decomposition stopped at 600 °C.     

Growth of Al2O3–PTFE composite film at room temperature by aerosol deposition method

To fabricate a ceramic-based substrate for 3-dimensional integration modules with a thick film coating process at room temperature, aerosol deposition method was employed. Al₂O₃ was chosen as a main coating material for the requirements of low permittivity and dielectric loss. Especially to give a functionality of plasticity, composite film with polytetrafluoroethylene (PTFE) was also studied. The effects of PTFE, which was incorporated in the film, were investigated by the microstructural characterization. It was confirmed that Al₂O₃–PTFE film with the grain size of 100–200 nm were grown at room temperature using Al₂O₃–0.5 wt% PTFE mixture powders. Dielectric constant and dielectric loss of Al₂O₃–PTFE film were 4.5 and 0.005 at 1 MHz, respectively.     

Preparation of polymer decorated graphene oxide by γ-ray induced graft polymerization

Herein, we report a facile approach to decorate graphene oxide (GO) sheets with poly(vinyl acetate) (PVAc) by γ-ray irradiation-induced graft polymerization. The content of PVAc in the obtained sample, i.e., PVAc grafted GO (GO-g-PVAc) is calculated by the loss weight in thermogravimetric analysis (TGA) curves. A GO-g-PVAc sample with a degree of grafting (DG) of 28.5% was well dispersed in common organic solvents and the dispersions obtained were extremely stable at room temperature without any aggregation, even after standing for 2 months. The excellent dispersibility and stability of GO-g-PVAc in common organic solvents are readily rationalized in terms of the full coverage of PVAc chains and solvated layer formation on graphene oxide sheets surface, which weakens the interlaminar attraction of GO sheets. This approach presents a facile route for the preparation of dispersible GO and shows great potential in the preparation of graphene-based composites by solution-processes.     

Effect of α- and γ-tocopherols on thermal polymerization of purified high-oleic sunflower triacylglycerols

The antipolymerization effects of α- and γ-tocopherols were compared in model systems composed of purified high-oleic sunflower triacylglycerols at 180°C. γ-Tocopherol was much more effective as an antipolymerization inhibitor than α-tocopherol, partly due to lower oxidizability/disappearance. Purified triacylglycerols of sunflower, rapeseed, and high-oleic sunflower oils were less stable than their nonpurified forms containing tocopherols. Results confirmed that tocopherols per se can act as antipolymerization agents in high-oleic oils at frying temperatures. No synergism was observed when α- and γ-tocopherols were present together although larger amounts of residuals were left for both tocols. Results suggested that high-oleic/high-γ-tocopherol oils (such as high-oleic canola and high-oleic soybean oils) may provide better frying oils than high-oleic/high-α-tocopherol oils (such as high-oleic sunflower oil).     

Novel Brønsted acidic ionic liquids catalyzed one-pot reaction of highly green regioselective thiocyanation of N-containing aromatic and heteroaromatic compounds at room temperature

In this method, a novel Brønsted acidic ionic liquid silica-supported pyridinium sulfonic acid thiocyanate {SiO₂@[Pyridine-SO₃H]SCN} and sulfonic acid-functionalized pyridinium chloride {[PSA]Cl} were easily synthesized and characterized. In the first method, {SiO₂@[Pyridine-SO₃H]SCN as a novel and environmentally friendly catalyst with one acidic functional group and one thiocyanation agent group was ef?ciently used for the synthesis of aryl and heteroaryl thiocyanates via the condensation of anilines, indoles, pyrroles, and their derivatives in the presence of H₂O₂ as a green oxidant in EtOH:H₂O (1:1) at room temperature. In the second method, {[PSA]Cl} as a new ionic liquid and environmentally friendly catalyst with one acidic functional group was used for the simple and efficient synthesis of aryl and heteroaryl thiocyanates via the condensation of anilines, indoles, pyrroles, and their derivatives with NH₄SCN in the presence of H₂O₂ as a green oxidant in EtOH:H₂O (1:1) at room temperature. A simple experimental procedure, clean reaction profile, use of an inexpensive catalyst, and recyclability of the catalyst are some of the advantages of the procedure. Also, one of the advantages of the first method is the non-usage of NH₄SCN or KSCN in the reaction.     

Synthesize of polyaniline–multi walled carbon nanotubes composite on the glass and silicon substrates and methane gas sensing behavior of them at room temperature

In this study, fabrication of methane gas sensor using composites of multi-walled carbon nanotubes (MWCNT) and polyaniline (PANI) on glass and silicon substrates is reported. In this respect, 8 wt% of purified MWCNT by acid washing procedure, was combined with PANI by solution mixing method. The MWCNT–PANI composite was deposited on the surface of glass and Si substrates using spin coating technique. The methane gas sensing of composite films were evaluated by measuring the change of electrical resistance in the presence of methane gas at room temperature. It is observed that the MWCNT–PANI film on the Si substrate shows a higher sensitivity to methane gas in comparison to pure PANI on the glass substrate. The characterization of samples has also been investigated by Fourier transform infrared, transmission electron microscopy and scanning electron microscopy analyses.     

Adsorption of carbon dioxide at high temperature—a review

In this review, the adsorption of carbon dioxide on adsorbent materials at high temperature is examined critically. Adsorbent materials including carbon-based adsorbents, metal oxide sorbents, zeolites and hydrotalcite-like compounds (HTlcs) for carbon dioxide at high temperature are discussed. Research areas, which may make a significant impact in future are put forward.     

A sol–gel approach for the room temperature synthesis of Al-containing micelle-templated silica

A two-step sol–gel method has been developed for the synthesis of Al-containing micelle-templated silica (Al-MTS) with Si/Al atomic ratios in the range 8–45. The synthesis proceeds at ambient temperature, atmospheric pressure, acid medium and for only 3 h. For the calcined materials, a decrease of both the d₁₀₀ spacing and the pore size, as well as an increase in the wall thickness, are observed with ncreasing aluminum content. Thus, the average pore size changed from 2.4 nm (Si/Al=45) to 1.4 nm (Si/Al=8), i.e. the pore size reaches the micropore range without varying the chain length of the surfactant used as micellar templating agent. The ²⁷Al NMR-MAS spectra show that in the as-synthesized samples the aluminum is present as tetrahedrally coordinated species, which are partially transformed into octahedral aluminum upon calcination. Since the synthesis takes place in the absence of alkali cations, the Al-MTS materials are directly obtained in the acid form, making a subsequent ion exchange and calcination treatments superfluous.     

Elastic properties of high alumina cement castables from room temperature to 1600°C

High-alumina refractory castables with compositions in the systems CaO–Al₂O₃ and CaO–Al₂O₃–SiO₂ were studied using an ultrasonic technique. The technique allows in-situ, non-destructive measurement of Young's modulus from room temperature to 1600°C. Elastic and dilatometric properties were investigated in relation to phase changes (followed by XRD) and sintering phenomena. The conversion of CAH₁₀, the hydration of still-anhydrous cement phases, and the dehydration of C₃AH₆ and AH₃ are related with events in Young's modulus evolution. Addition of 1 wt% of silica fume strongly decreases the high-temperature mechanical properties.     

RAFT-mediated polymerization and grafting of sodium 4-styrenesulfonate from cellulose initiated via γ-radiation

Ambient temperature (20 °C) reversible addition fragmentation chain transfer (RAFT) polymerization of sodium 4-styrenesulfonate (SS) conducted directly in aqueous media under γ-irradiation at different dose rates (0.09, 0.03 and 0.02 kGy h⁻¹) proceeds in a controlled fashion (typically, M_w/M_n < 1.25) to near quantitative conversions via 4-cyanopentanoic acid dithiobenzoate (CPADB) mediation. By applying CPADB modified cellulose as a macro chain transfer agent, a graft copolymer with SS was prepared in aqueous media under γ-irradiation. RAFT mediated graft polymerizations provided copolymers with higher graft frequencies compared to those obtained by conventional methods. Thermally initiated grafting of SS from a CPADB-functionalized cellulose surface at 70 °C was also studied which resulted in a reduced graft frequency in comparison to γ-initiated ones.     

Preparation of the γ-Al2O3/PANI nanocomposite via enzymatic polymerization

Peroxidase-catalyzed template-guided polymerization of aniline in the presence of γ- alumina nanosheet (NS) particles have been carried out in aqueous media and γ-Al₂O₃/PANI nanocomposite was obtained. The polymerization of aniline occurred in aqueous solution in the presence of SPS (sulfonated polystyrene) as a template and SDS (sodium dodecyl sulfate) as a surfactant. Both obtained nanocomposites were comparable by SEM images. It was demonstrated that the γ-Al₂O₃ NS/PANI-SPS nanocomposite has higher conductivity and the γ-Al₂O₃ NS/PANI-SDS nanocomposite has higher void areas. The higher conductivity of γ-Al₂O₃ NS/PANI-SPS nanocomposite is attributed to the higher coated areas of γ-Al₂O₃ NS during polymerization in comparison with γ-Al₂O₃ NS/PANI-SDS which are not coated efficiently as the former. The FT-IR studies showed that the γ-Al₂O₃ NS/PANI nanocomposite was formed by interaction of the polyaniline (PANI) and γ-Al₂O₃ NS. FTIR also showed that the amount of PANI in γ-Al₂O₃ NS/PANI-SPS is more than in γ-Al₂O₃ NS/PANI-SDS. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Low temperature firing of Co2Y–NiCuZn ferrite composites

Hexagonal structure magnetoplumbite ferrites have revealed a higher dispersion frequency than that of nickel ferrites because of the magnetoplumbite's magnetic anisotropy. The magnetoplumbite ferrite densification temperature always exceeds 1000 °C and the initial low temperature firing permeability of magnetoplumbite ferrites with added glass is too low (μ_i = 2–4). Therefore, it is desirable to develop a material that has a higher permeability at above 300 MHz and can be densified at temperatures below 900 °C. The Bi₂O₃–B₂O₃–ZnO–SiO₂ (BBSZ) glass addition effects on the densification and magnetic properties of Co₂Y–NiCuZn ferrite composites with various Co₂Y/NiCuZn ferrite ratios were investigated. The densification of Co₂Y–NiCuZn ferrite composites was enhanced by the addition of glass at low sintering temperatures (<900 °C) due to the liquid phase sintering. Co₂Y–NiCuZn ferrite composites with 4 wt% BBSZ glass sintered at 900 °C show a relative density above 90%, a high-initial-permeability of 5–6, a quality factor of above 30 in the 200–300 MHz frequency and a resonance frequency above 1 GHz, which can be used in high frequency multilayer chip inductors.     

Sol–gel synthesis of Pd doped ZnO nanorods for room temperature hydrogen sensing applications

A sol–gel spin coating technique was described for the synthesis of Pd doped ZnO nanorods for hydrogen sensing applications. The nanorods were hexagonal in shape, 50–100 nm in diameter and uniform in distribution. They exhibited homogeneous surface morphology, c-axis orientation and excellent crystalline properties. The synthesized nanorods were used to sense and detect hydrogen in a homemade gas chamber. The fabricated sensor successfully detected as low as 40 ppm hydrogen at room temperature with a very low level of power supply (16.16 μA) under a mixed background. Dynamic and repeated responses were observed with a wide range of hydrogen concentrations (40–360 ppm) at 200 °C. The developed sensor was at least 25 fold more sensitive over the literature documented Pd doped ZnO nanorods in detecting hydrogen at ambient temperature. The simplicity, low-cost, high sensitivity and high stability of the sensor materials suggested that the synthesized Pd doped ZnO nanorods could be used in hydrogen and chemical sensing devices where Pd-mediated catalysis is involved.     

New equation of ΔHbi for organic compound at different temperature

阐明Watson公式的不足和缺陷,应用分子热力学理论揭示出液体的汽化热取决于液体的分子间相互作用力,导出预测不同温度下有机纯质汽化热的新方程,其物理意义明确.经用39种结构类型的310个实验值检验,平均误差0.69%.Watson式为3.06%,本法的精度比Watson式高4.4倍以上.     

Synthesis of ambient temperature self-crosslinking VTES-based core–shell polyacrylate emulsion via modified micro-emulsion polymerization process

Modified micro-emulsion polymerization was successfully used to synthesize a kind of ambient temperature self-crosslinking core–shell emulsion, consisting of polyacrylate core and vinyltriethoxysilane (VTES) modified polyacrylate shell, by varying the ratio of soft monomer (BA) and hard monomer (MMA) which is different in the core and shell. The emulsion and its film formed at ambient temperature were characterized by attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Core–shell structure was clearly shown in TEM micrographs, and two distinct glass transition temperatures (T _g) were confirmed by DSC analysis. Lower T _g of core phase analyzed by DSC and self-crosslinking properties of VTES characterized by crosslinking degree cause latex particles form continuous film at ambient temperature. Thermal and mechanical properties and the surface properties of the latex films were also investigated. Results showed that the core–shell latex films containing 5 and 7.5 % VTES exhibited higher thermal stability, better mechanical properties, higher contact angle, and water resistance compared with pure polyacrylate film.     

Blue and red light photoluminescence emission at room temperature from CaTiO3 decorated with α-Ag2WO4

CaTiO₃ (CT) and α-Ag₂WO₄ (AW) semiconductors are widely known for their interesting electrical and photoluminescence (PL) properties. In this study, we decorated CT with AW for obtaining CaTiO₃:α-Ag₂WO₄ (CT:AW), and investigated the properties of the produced materials, especially their PL properties. The X-ray diffraction peaks of the synthesized microcrystals were well indexed to the orthorhombic phase for all the samples. Two morphologies: cube-like for CT and rod-like for AW were observed by field-emission scanning electron microscopy (FE-SEM). The FE-SEM and transmission electron microscopy (TEM) studies indicated the presence of rod-shaped AW deposited on the surfaces of cube-shaped CT morphology. PL emission of the decorated samples overlaps all the visible region spectra because of the contribution from both the constituent materials that induce maximum emissions in the blue and red regions. The examination of Commission internationale de ĺéclairage (CIE) coordinates confirmed that the decorated samples exhibit favored emission the red wavelength region.