Alkyl-substituted dipyrrylmethenes and their oxa- and thia-analogs: “structure—solvation properties” correlations

New data on the spectral properties and solution enthalpies of unsymmetrically substituted 2-(alkyl-2-pyrrolylmethylidene)methylpyrrolium bromides (or ,-dipyrrylmethene hydrobromides), their ,-, ,-isomers, as well as their oxa and thia analogs, that is, 2-(2-furylmethylidene)- and 2-(2-thienylmethylidene)-3,4,5-trimethyl-1H-pyrrolium bromides, in solutions of organic solvents of different nature are presented. A decrease in the number of substituents, as well as replacement of the heteroatom (N) in one five-membered ring of the dipyrrylmetnehe by oxygen or sulfur atoms cause a monotonic hypsochromic shift of absorption bands in the electronic absorption spectrum and weakening of the chromophore properties of the compounds. The chromophore properties of isomers are weakened from the ,- to ,- and ,-dipyrrylmethenes. Main trends in the influence of structural factors on the specific features of thermooxidative destruction of the above-mentioned compounds were analyzed.     

Chiroptical properties of 12,15-dichloro[3.0]orthometacyclophane—correlations between molecular structure and circular dichroism spectra of a biphenylophane

The valence excited electronic states and the circular dichroism (CD) spectra of the recently synthesized 12,15-dichloro[3.0]orthometacyclophane 1 are discussed by means of quantum chemical calculations which combine density functional theory with the single-excitation configuration interaction approach (DFT/SCI). The X-ray structure of this highly strained biphenylophane is presented. In order to investigate the influence of the cyclophane-type distortions on the CD spectrum of 1, the CD spectra of three model geometries (2a–2c) are also calculated. It appears that the CD spectrum of the biphenylophane 1 differs substantially from that of the corresponding unstrained biphenyl 2c. Furthermore, it is found that the pyramidalization of the bridging atoms of the cyclophane ring is an important factor for the red shift of the first band with respect to that of an unstrained benzene chromophore.     

Antioxidants and stabilisers LXXXIII photoinitiating properties of alkylperoxycyclohexadienones in trimethylcyclohexane—A model of polypropylene

1,3,5-trimethylcyclohexane (TMCH) was used as a liquid model of polypropylene in the investigation of the photoinitiating properties of some transformation products, such as alkylperoxy T-T (I), hydroperoxy (II), hydroxycyclohexadienones (III), and stilbenequinone (V), formed from phenolic antioxidants in the process of stabilisation. I and II rank among the most powerful photoinitiators of alkane oxidation at 366 nm, where the amount of light absorbed by the alkyl hydroperoxides present is already very low. The initial rate of photo-oxidation decreases due to the phototransformation of the starting material (I) into cyclopentadienone (IV) with screening properties similar to those of stilbenequinone (V).     

Qualitative spectroscopic characterization of the matrix–silane coupling agent interface across metal fibre reinforced ion exchange resin composite membranes

The characterization of novel metal reinforced electro-dialysis ion exchange membranes, for water desalination, by attenuated total reflectance Fourier transform infrared spectroscopy mapping is presented in this paper. The surface of the porous stainless steel fibre meshes was treated in order to enhance the amount of surface oxide groups and increase the material hydrophilicity. Then, the metal membranes were functionalized through a sol–gel reaction with silane coupling agents to enhance the affinity with the ion exchange resins and avoid premature metal oxidation due to redox reactions at the metal–polymer interface. Polished cross sections of the composite membranes embedded into an epoxy resin revealed interfaces between metallic frameworks and the silane layer at the interface with the ion exchange material. The morphology of the metal–polymer interface was investigated with scanning electron microscopy and Fourier transform infrared micro-spectroscopy. Fourier transform infrared mapping of the interfaces was performed using the attenuated total reflectance mode on the polished cross-sections at the Australian Synchrotron. The nature of the interface between the metal framework and the ion exchange resin was shown to be homogeneous and the coating thickness was found to be around 1 μm determined by Fourier transform infrared micro-spectroscopy mapping. The impact of the coating on the properties of the membranes and their potential for water desalination by electro-dialysis are also discussed.     

Electrical properties of elastomer-based composites reinforced with carbon nanotubes—A review

Even though carbon nanotubes offer an excellent solution for the design of strain sensors, their widespread commercial utilization has been hampered by the unavailability of design rules, inconsistencies in their macro-scale properties, and lack of understanding of the effects of various parameters on their characteristics. Nevertheless, many researches have been carried out to characterize elastomeric nanocomposites filled with carbon nanotubes in order to optimize their properties such as electrical conductivity and strain sensitivity range. This article reviews the effect of different parameters on the electrical properties of such nanocomposites, followed by the analysis of performances of elastomer strain sensors.     

Rheological and DSC Studies on the Interaction between k-Carrageenan and Cellulose Nanocrystals （CNC）

Rheometer and differential scanning calorimetry （DSC） have been used to probe the mechanism of gelation in gels formed by mixture of k-carrageenan and cellulose nanocrystals （CNC）. The results indicated that an association occurred between CNC chains and aggregated k-carrageenan helices.     

Rheological and DSC Studies on the Interaction between κ-Carrageenan and Cellulose Nanocrystals (CNC)

The κ-carrageenan comes from a family of linear water-soluble polysaccharides extracted from different species of marine red algae with a primary structure of an alternating disaccharide with repeating unit of 3-linked β-D-galactose 4-sulfate and 4-link…     

Electrochemical synthesis and properties of iron–titanium dioxide composite coatings

Deposition of Fe/TiO₂ composite coatings from a colloidal methanesulfonate electrolyte containing titanium dioxide hydrosol was studied. The TiO₂ content in the composite increases with increasing the dispersed phase content and decreasing the current density. Incorporation of TiO₂ particles into the iron matrix resilts in an increase in the microhardness of the deposit. The electroplated Fe/TiO₂ composite coating was used as a heterogeneous photocatalyst for the decomposition of an organic dye under the action of UV radiation.     

What is the technical and environmental interest in reusing a recycled polypropylene-hemp fibre composite?

The integration of the environmental problem in the design of industrial products leads us to incorporate vegetal fibres and recycled polymers into composite materials. The aim of this work is to study the behaviour and the environmental interest of a recycled PP/hemp fibre after several injection cycles. The mechanical and rheological behaviour of recycled PP/hemp composite was first studied by using tensile, dynamical mechanic analysis and rheological measurements. Then, to better understand the influence of the recycling, a morphology study was carried out on composites by using optical and electron microscopy. Finally, we investigated the environmental advantages of our composite thanks to a simplified environmental assessment. Our results highlighted the environmental interest of using a recycled matrix to prepare composites reinforced with vegetal fibres and the interesting properties of this material after recycling.     

Mechanical properties and crystallization behavior of polypropylene with cyclodextrin derivative as ��-nucleating agent

It was found that lanthanum complex of cyclodextrin derivative (??-CD?CMAH?CLa) was a highly active ??-nucleating agent for isotactic polypropylene (iPP) in this study. The influence of the nucleating agent on mechanical properties and isothermal and nonisothermal crystallization behavior of iPP has been investigated. Results showed that ??-CD?CMAH?CLa was efficient in inducing the crystallization of iPP into ??-modification (??-iPP), with K _?? value of 0.84, while the content of nucleating agent was 0.8?wt.%. ??-iPP could form extensively in the isothermal crystallization temperature range from 110?°C to 140?°C, and the highest amount of ??-crystal content was formed at 130?°C. Besides, it can be known that the addition of ??-CD?CMAH?CLa can obviously facilitate the overall crystallization process of iPP. Under nonisothermal condition, ??-iPP formed at the suitable cooling rates, ranging from 5?°C to 10?°C/min. Furthermore, the nucleation mechanism of ??-CD?CMAH?CLa for iPP was correlated to the special configuration of ??-CD?CMAH?CLa.     

Physicochemical properties and catalytic activity of metal–carbon carrier composite materials

Composite metal–carbon materials are created on the basis of different kinds of carbon (multiwall carbon nanotubes, carbon black, Sibunit carbon–carbon material) and metals (Ag, Ni, Co), and their physicochemical and catalytic properties are investigated. It is shown that interaction between metals and carbon carriers proceeds not only with the functional groups on the surfaces of the carriers, but also through a system of–C–C–conjugated bonds. Silver deposited on the surface of a carbon carrier has a crystalline structure (d _cr = 10–15 nm), while nickel has an amorphous lamellar structure. Based on quantum-chemical calculations using the density functional theory, it is shown that cumene oxidation occurs via a homogeneous–heterogeneous mechanism.     

Preparation and properties of Al?B?Si composite pillared bentonite

Al–B–Si composite pillared clay was first prepared and its catalytic cracking properties for gas oil were investigated. Characterization techniques included XRD, BET and IR spectroscopy of pyridine adsorbed. It is shown by the results that the introduction of Si enhanced the catalytic activity and gasoline yield on pillared clay. Al–B–Si composite pillared clay was a better catalyst material.

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Fe_3O_4/Au composite nano-particles and their optical properties

The colloid gold and magnetic particle modified with various chemical groups have been widely used in the areas of biomedical and molecular biology[1―6]. Therefore, a great deal of attention has been given to the preparation and application of colloid go…     

Production and properties of polyacenaphthylene—V dilute solution properties

Polyacenaphthylene was synthesized by thermal bulk polymerization, fractionated into 11 fractions by fractional precipitation and characterized by gel permeation chromatography, light scattering and osmometry. Long chain branching was observed in polyacenaphthylenes with $\text{M}{}_{\mathrm{<mtext>w</mtext>}}\text{> 1 × 10}{}^6\text{g/mol}$. θ-temperatures of branched and linear polyacenaphthylenes were determined in 1,2-dichloroethane and are different in magnitude. Polyacenaphthylene undergoes chemical degradation in manufacturers' grade 1,2-dichloroethane. Intrinsic viscosities in benzene, toluene, tetrahydrofuran at 25°C, and in 1,2-dichloroethane at 41.1°C have been measured and the Mark-Houwink constants of the viscosity molar mass relationship evaluated.     

The effect of fibre diameter on filtration and flux distribution — relevance to submerged hollow fibre modules

This paper examines the effect of fibre diameter on filtration and flux distribution with inter-fibre two-phase flow for conditions relevant to submerged bioreactors (SMBR). Hollow fibres of different diameters fixed in a specially designed holder providing shell-side feed were tested for a model biomass feed with pumping and submerged systems. The experimental results showed that the effect of the fibre diameter on filtration increased with the increase in turbulence around the fibres. For filtration with two-phase flow, the performance was sensitive to changes in fibre diameter and significantly lower flux declines were obtained with smaller fibres. On the other hand, a theoretical analysis of flux distribution along the fibre in a submerged system showed the smaller fibres to be disadvantaged. The theoretical model based on the simplified Navier–Stokes equations and filtration equations revealed that the flux distribution along the fibre depends on fibre inner diameter, length and fibre permeability. The effect of these factors can be related to a dimensionless coefficient ζ=4lR_i^−3/2R_m^−1/2. Sensitivity analysis demonstrated that for ζ>2, the maximum flux along the fibre can be approximately estimated by J_max=ζJ_mi. Although, the effect of high initial local flux on performance of filtration is still to be assessed, the flux distribution model is useful in design and operation of the SMBR system.     

Mechanical properties,surface morphology and failure mode of γ-ray irradiated blends of polypropylene and ethylene-vinyl acetate rubber

The effect of ⁶⁰Co γ-radiation on the mechanical properties, surface morphology and failure characteristics of blends of polypropylene [PP] and ethylene-vinyl acetate rubber [EVA] has been studied with specific reference to the effect of blend ratio, dynamic crosslinking of the rubber phase and absorbed radiation doses. Samples were subjected to radiation in the dose range of 1 to 100 Mrad in air at room temperature at the rate of 0·321 Mrad/h. Both chain scission and crosslinking occur simultaneously in the blend samples. PP and blends containing higher proportions of PP (≥50%) undergo predominant chain scission at lower doses (≤50 Mrad), which causes a drastic drop in tensile strength, followed by a levelling out at higher doses of 100 Mrad. EVA undergoes crosslinking at lower doses resulting in an increase in tensile strength in the dose range 1 to 10 Mrad followed by a decrease in the range 10–25 Mrad. Further increase in radiation dose has little effect on tensile strength. The effect of radiation on stress-strain behaviour, elongation at break, energy at rupture and hardness was also studied. The morphology of the irradiated surfaces after an absorbed dose of 100 Mrad has been examined by scanning electron microscopy (SEM). In order to understand the effect of γ-radiation on the failure mechanism, tensile failure surfaces of both unirradiated and irradiated samples have also been examined by SEM.     

Investigations in annealing effects on structure and properties of β-isotactic polypropylene with X-ray synchrotron experiments

The influence of annealing on the microstructure and mechanical properties of β-form isotactic polypropylene (iPP) was investigated via in situ synchrotron small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC). Transition of β-iPP to α-iPP was investigated via recrystallization at high annealing temperatures (T _a?>?120 °C). And crystallinity, crystal sizes, and long period of ordered structure increased with increasing annealing temperature. Abrupt changes were found in both mechanical properties and structural features at the same T _a range (～120 °C). The in situ synchrotron SAXS and WAXD shows that the destruction of b phase at yielding and after yielding should account for the ductility of β-iPP. The thermodynamics and kinetics of annealing were investigated with DSC and X-ray synchrotron experiments. A characteristic annealing time was investigated, which measures the rate of phase evolution in annealing of β-iPP. Eventually, a hypothesized model can be used to describe the property/structure relations during this process.