Dynamic (hyper)polarizability calculations for polymers with linear and cyclic π-conjugated elementary cells

Static and dynamic (hyper)polarizabilities for polymers built up from HCCR with RH, OH, F have been calculated with the perturbed coupled Hartree–Fock method. At this level polyacetylene (PA) has the highest polarizability, but the inclusion of the electron correlation correction interchanges the ordering and the fluorinated system becomes the most polarizable one. This shows that these contributions cannot be neglected. We have investigated the series of polymers arising from the cyclic five-membered molecules pyrrole, furane, and thiophene and in addition polyparaphenylene (PPh) and polyaniline (PAn). The basis set dependence and the effect of the number of neighbors interaction have been studied. It turns out that polythiophene (PTh) is easier to polarize than polyparaphenylene, polypyrrole (PPy) and polyfurane (PFu). The correlation contribution does not change the sequence. Polyaniline in its neutral all-trans configuration shows the highest static and dynamic polarizabilities due to the very extended π-electron system of the elementary cell. In addition, the static and dynamic polarizabilities of the constituent molecules pyrrole, furane, thiophene and benzene have been calculated for comparison with the corresponding polymers.     

Synthesis and characterization of two-armed poly(ɛ-caprolactone) polymers initiated by the Schiff's base complexes of copper(II) and nickel(II)

Two-armed poly(?-caprolactone) (TAPCL) polymers were successfully synthesized via the ring opening polymerization (ROP) of ?-caprolactone (?-CL) using the Schiff's base complexes [Cu(SAEE)₂] (1) and [Ni(SAEE)₂] (2), which have two hydroxyl functional groups, as the two-site initiators and tin(II) 2-ethylhexanoate (Sn(Oct)₂) as the catalyst in bulk at 115 °C. The Schiff's base complexes (1 and 2) were synthesized by utilizing the concentrated template synthesis method starting from salicyl aldehyde, 2-(2-aminoethoxy) ethanol and related metal acetate salts. The synthesized TAPCL polymers were characterized by GPC, FTIR, UV–vis, and electron paramagnetic resonance (EPR). The molecular weights of TAPCL polymers linearly increased with increasing molar ratio of the monomer to the initiator. The results obtained from FTIR, UV–vis, and EPR studies indicated that TAPCL polymers had the Schiff's base complexes at the junction point of PCL arms. The crystallization behavior of TAPCL was studied by using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Thermal behavior of TAPCL was also investigated by thermogravimetrical analysis (TGA).     

In the search of an electron transfer between π-donors and C60: the bis-linking of tetrathiafulvalene (TTF) to C60

In order to realize the bis-linking of tetrathiafulvalene (TTF) to one or two C₆₀, and to reach the dyad compounds 1 and 2, the [4 + 2] Diels-Alder reactions of C₆₀ with orthoquinodimethanic derivatives of 1,3-dithioles 5a,b or TTF 9 are studied.     

Investigation on the syntheses and structures of Y~(Ⅲ) complexes with ami-nopolycarboxylic acids (Ⅳ)

This paper deals with the structure of the YIII complex with aminopolycarboxylic acids, synthesis and structural determination of the complex (NH4)[YIII(edta)(H2O)3]·3H2O (edta = ethylenediaminetetraacetic acid). The crystal and molecular structures of the (NH4)[YIII(edta)(H2O)3]·3H2O complex have been determined by single-crystal X-ray structure analysis. The crystal of the complex (NH4)[YIII(edta)(H2O)3]·3H2O belongs to orthorhombic crystal system and fdd2 space group. The crystal data are as follows: a=1.944 1(9) nm, b= 3.545 9(18) nm, c = 1.219 6(6) nm, V= 8.407 (7)nm3,Z=16, Mr= 503.25, Dc= 1.590g.cm3, μ= 2.844 mm 1 and F(000) = 4 160. The final R and Ru are 0.048 6 and 0.133 2 for 3 388 (I>2σ(I)) unique reflections, respectively. The complex anion [YIII(edta)(H2O)3] has a pseudo-mono-capped square antiprismatic nine-coordinate structure in which the six coordinate atoms (two N and four O) are from an edta ligand and three water molecules coordinate to the central YIII ion directly. From the res     

Engineering the biological performance of hierarchical nanostructured poly(ε-carpolactone) scaffolds for bone tissue engineering

Scaffolds play an important role as physical substrates for cell proliferation and differentiation, leading to tissue regeneration. For bone applications, researchers are focusing on cellular or acellular biocompatible biodegradable polymeric scaffolds. However, high biological performance scaffolds are still required to meet actual clinical demands. This paper discusses a novel strategy to engineer the biological performance of polymeric scaffolds through the combined use of additive manufacturing, acetone vapour annealing surface treatment and dopamine grafting, enabling the fabrication of hierarchical nanostructured tissue engineering structures. Produced scaffolds present improved biological behaviour compared to conventional additive manufactured scaffolds, and similar mechanical properties, showing high potential for clinical applications.     

Synthesis of the dendronized poly(p-phenylenevinylene) with appendent Fréchet-type dendrons

The dendronized poly(p-phenylenevinylene)s (PPVs) with appendent Fréchet-type dendrons were successfully synthesized, and characterized by laser light scattering (LLS), thermogravimetric analysis (TGA), UV-Vis and fluorescence spectra.     

The Effect of 2,2′- and 4,4′-Dipyridyl on the Electroreduction of Cu(II) from Basic Solutions of Ethylene- diaminetetraacetic Acid (EDTA)

The results are presented of investigation of the effect of 2,2′- and 4,4′-dipyridyl on the potential-current characteristics of cathodic electroreduction of copper(II) from basic solutions of EDTA. The applied heterocyclic bases exhibit very similar capabilities of sorption on metallic electrodes, whereas they differ significantly in their abilities to complex copper(II) ions. It was found by the chronovoltammetric method that the addition of 2,2′-dipyridyl in the range of concentration from 5*10^?7 to 10^?5 M substantially accelerates the cathodic reduction of copper. However, the presence of 4,4′-dipyridyl brought about a decrease of the reduction current peak within the concentration range investigated i.e. 10^?7 ÷ 5*10^?4 M under the same experimental conditions. The different interaction of the ligands during the electroreduction of Cu-EDTA complexes was explained in terms of their different complexing properties. It was found that when the concentration of 2,2′-dipyridyl was comparable to the concentration of EDTA a new cathodic peak appeared on the polarization curves, due to the reduction of Cu(II)-2,2’ dipyridyl complex.     

Kinetic spectrophotometric method for the determination of cerium(Ⅳ) with naphthol green B

A simple and sensitive spectrophotometric method was described for the determination of cerium(Ⅳ) based on its catalytic effect on the oxidation of naphthol green B by potassium periodate in the medium of sulfuric acid. The influences of acidity, concentration of reactants, reaction time, reaction temperature, and foreign ions were discussed, and the optimum reaction conditions were established. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of naphthol green B at 710 nm after a fixed time (8 min). The separation. Recovery experiments were also performed, and the recovery was between 95.7%-111.0%.     

Sensitizing Effect of Mixed Surfactants on the Colouration of Scandium(Ⅲ)with Phenylfluorone or Its Derivatives

In the presence of mixed micelle of a cationic and a nonionic surfactants,the reaction of scandium(Ⅲ)with phenylfluorone or its derivatives results in a very sensitive colouration:furthermore this chromophoricsystem tolerates the existence of a considerable amount of masking agents,so that many interfering ions can bemasked and its selectivity would be further improved.After studying the optimum conditions and main charac-ters of some similar systems,the system of Sc(Ⅲ)—Orthonitrophenyuorone—CetyltrimethylammoniumBromide(CTMAB)—Triton X-200 is chosen for the spectrophotometric determination of microamount ofscandium.The proposed method shows not only high sensitivity(with a molar absorptivity of 2.12×1~sLmol~(-1)·cm~(-1))and selectivity,but also high tolerance of chromophoric conditions.Beer's law is obeyed over arange of 0～6.0 μg Sc/25ml.If the dual-wavelength method is applied,a much higher molar absorptivity o|"3.04×10~5L·mol~(-1)·cm~(-1)than those of other systems ever reported in the literatures can be attained:more-over.its linear range is extended to 0～8.0 μg Sc/25ml and its reproducibility is also improved.     

The Effect of Chemiadsorbed Layers of Nitrilotris–Methylenephosphonate Complexes of Lead(II) with Bridging and Chelate Coordination on the Electrochemical Behavior of a Steel 20 Surface. Thermochemical Induction of Secondary Inhibition

Protection of Metals and Physical Chemistry of Surfaces - The effect of the chemiadsorbed layers of two lead(II) complexes of nitrilotris–methylenephosphonic acid, differing from one another...     

Effect of Cu(II) on the formation,morphology and molecular adsorption properties of α-FeOOH rust particles prepared from acidic Fe(III) solutions

To simulate the atmospheric corrosion of weathering steels, α-FeOOH rust particles were synthesized from acidic Fe(NO₃)₃ solutions in the presence of Cu(II) at 50 °C. No remarkable change of crystallinity of α-FeOOH was observed by adding Cu(II). Increasing the added Cu(II) formed the nano-sized ferrihydrite particles and reduced the size of α-FeOOH particles, leading to the increase of specific surface area. The Cu(II) added in the starting solution was less easily incorporated in the particles than Fe(III). The adsorption of corrosive gasses such as H₂O, CO₂ and SO₂ on the rust particles was inhibited by the addition of Cu(II).     

Improving fatigue performances of structures welded using the Stressonic® (ultrasound peening) compared with the tig refusion process

A new coaxial plasma MIG welding system is developed for the purposes of improvement of weld bead, reduction of spatter and fume generation. Welding power sources of MIG and plasma, wire feeding equipment and a coaxial plasma MIG welding torch are described in detail. The metal transfer of plasma MIG welding in aluminium is observed and compared with that of pulsed MIG welding. Although one droplet per pulse is obtained by both processes, plasma MIG welding shows more smooth metal transfer than pulsed MIG welding. The result shows that spatter and fume generation are drastically reduced, and clean and good weld bead appearance is obtained by the new system.     

Solid-phase extraction of trace Au(Ⅲ) with SDG and determination by the catalytic spectrophotometric method

The new catalytic kinetic spectrophotometric method for Au(Ⅲ) determination was developed and validated.It was based on the catalytic effect of gold on the oxidation of sudan red Ⅲ by ammonium peroxodisulfate ((NH4)2S2O8) with nitrilo triaeetic acid as an activator in microemulsion and H2SO4 medium.Under optimum conditions,there was the linearity of the calibration curve in the concentration range from 0 to 20 μg/L Au(Ⅲ) at 520 nm.The relative standard deviation was 3.0% with a correlation coefficient of 0.9986.The detection limit achieved was 9.75×10-5 μg/mL.A new method using a column packed with sulfhydryl dextrose gel (SDG) as a solid-phase extraetant has been developed for the preeoncentration and separation of Au(Ⅲ) ions.The method has been applied to the determination of trace gold with satisfactory results.     

Friction riveting (‘FricRiveting’) of 6056 T6 aluminium alloy and polyamide 6: influence of rotational speed on the formation of the anchoring zone and on mechanical performance

Metal-polymer hybrid structures can be used as an alternative solution for reducing weight and fuel consumption in the transport industry, which aims to minimise the emission of harmful gases that have a greenhouse effect. Friction riveting is a relatively new technique for joining metal-polymer hybrid structures. The process is based on the generation of frictional heat between the components, resulting in the plastic deformation of the end of the metal rivet, which is anchored inside the polymer component. This study assessed the technical feasibility of joining AA 6056 T6 and PA6, focusing on the influence of the rotational speed of the rivet on the mechanical performance of the joints. The maximum temperature reached during the process increased with the rotational speed, from 291 ± 6 °C with 10,000 rev/min to 375 ± 5 °C with 15,000 rev/min. The use of higher rotational speeds led to the tip of the rivet undergoing plastic deformation during the friction phase. This produced mechanically stronger joints, because the metal rivet was anchored more securely in the polymer block. The AA 6056 T6-PA6 joints perform well in terms of tensile strength, reaching 85% of the tensile strength of the metal rivet. We therefore confirmed that it is possible to join AA 6056 T6 and PA6 using the technique of friction riveting, and that rotational speed directly affects the tensile strength of the joints.     

Influence of post-weld heat treatment (PWHT) on the structure and properties of welded joints of chromium–nickel stainless steel with soft martensite

This paper reviews the results of investigations on how post-weld heat treatment (PWHT) influences the hardness and microstructures of welded joints in stainless steel X3Cr-NiMo 13-4. It is known that welding leads to high segregation of components in the solidification process, which has an influence on phase transitions in PWHT. The investigated steel has a very narrow PWHT range, about 600–620°C, which provides optimum levels of hardness and toughness. Excessive annealing temperature leads to decreased toughness, which in turn causes exceeding of the A_c1 temperature in the segregation range, which then leads to increased ‘fresh’ martensite content.     

Metal (3d)–organic (2p)-hybrid magnets made of Mn(II) ions with tris(aminoxyl) radicals (R’s) as bridging ligands: 2D complexes [{Mn(hfac)2}3·R2]

The magnetic properties of three 2D-network complexes [{Mn(hfac)₂}₃·R₂] have been studied. Tris(aminoxyl) radicals R’s have quartet ground states and contribute not only to the formation of the extended network structures but essentially to the overall magnetism. Antiferromagnetic interactions between Mn(II) and the aminoxyl radicals and ferromagnetic intraradical aminoxyl–aminoxyl interactions both within the layer are responsible for the development of the characteristic magnetic properties in these heterospin systems. Depending on the nature of interlayer interactions, they show either ferro/ferrimagnetic or antiferromagnetic long-range order. The hierarchy of the different exchange interactions is established and the Mn–aminoxyl exchange integrals were evaluated from analysis of the temperature dependence of their paramagnetic susceptibility. With increasing intraradical exchange interaction, the complexes exhibit a clearer 2D behavior.     

The Effect of Sulfur Segregation on the Adherence of the Thermally-Grown Oxide on NiAl—II: The Oxidation Behavior at 900°C of Standard,Desulfurized or Sulfur-Doped NiAl(001) Single-Crystals

In Part II of this study, the characterization by TGA, SEM and AFM of the oxidation behavior at 900°C of NiAl(001) samples with various sulfur concentrations is reported. The formation of interfacial cavities is observed for all samples. A constant ratio of the oxide thickness to cavity depth is found showing that the formation of cavities at the metal–oxide interface is not due to sulfur but only to vacancy injection during the cationic growth of transient -alumina. It is also observed that the presence of sulfur in the alloy decreases the oxidation rate of the nickel aluminide and, consequently, lowers the formation of interfacial cavities. This effect is interpreted as an indirect evidence of the control of the transient-alumina growth by the aluminium diffusion in the alloy, also advanced as an explanation for the interfacial nucleation of alpha alumina. These results are combined with those presented in Part I to propose a model that explains how sulfur, present in small quantities in the alloy, has a deleterious effect on the oxide adherence. The indirect role of the cavities formed during the growth of the transient alumina is to create transitory conditions for the rapid segregation of sulfur at the interface. The segregated sulfur remains as a vestige of the initial stages of growth after the transformation of the scale into mature alumina and weakens its adherence.     

Preparation of NH4ZrH(PO4)2·H2Ovia solid-state reaction at low heat and its catalytic performance in the synthesis of butyl acetate

Nanocrystalline NH4ZrH(PO4)2·H2O was obtained by grinding ZrOCI2·8H2O and (NH4)2HPO4 in the presence of surfactant PEG-400 via solid-state reaction at room temperature.The product NH4ZrH(PO4)2·H2O and its product of thermal decomposition were characterized using thermogravimetry and differential thermal analyses (TG/DTA),Fourier transform infrared spectroscopy (FT-IR),X-ray powder diffraction (XRD),and transmission electron microscopy (TEM).Nanocrystalline NH4ZrH(PO4)2·H2O with an average particle size of 17 nm was obtained when the product was kept at 80℃ for 3 h.Its crystalline framework was stable at temperatures below 250℃.In addition,the catalytic performance of NH4ZrH(PO4)2·H2O in the synthesis of butyl acetate was investigated.The results show that NH4ZrH(PO4)2·H2O behaved as an excellent heterogeneous catalyst in the synthesis of butyl acetate.     

Kinetic Features of Iron Oxidation in Liquid Lead Saturated with Oxygen Below and Above the Chaudron Point (570 °C)

The oxidation kinetics of Armco–Fe in stagnant lead melts saturated with oxygen at 550 and 650 °C was investigated and the peculiarities of structure, phase and elemental composition of scales were determined. At 550 °C oxidation follows a parabolic law up to 1,500 h and then (1,500–2,000 h) oxidation accelerated. At 650 °C during 100 h the scale grew rapidly according to a quadratic time dependence. Then (100–500 h) the oxidation rate decreased sharply. From 500–1,000 h oxidation accelerated. The scales formed at 550 and 650 °C consisted of Fe₃O₄ and FeO/Fe₃O₄, respectively. The scales had a duplex structure. The outer-oxide layer grew from the initial solid metal–liquid metal interface towards the melt while the inner layer grew towards the iron substrate. The defectiveness of scale altered with time. The possible reaction mechanisms in the Fe–Pb[O] system are discussed.