Langmuir-blodgett films containing carotenoid dye. I. Preparation and characterization of ethyl β-Apo-8-carotenoate/cadmium stearate LB films

This article describes the preparation and characterization of ethyl β-apo-8-carotenoate dye/cadmium stearate mixed Langmuir—Blodgett films. The Wilhelmy plate method, FTIR spectroscopy, and contact angle measurements were the principal techniques utilized. Incorporation of cadmium stearate was observed to be critically important to the formation of ethyl β-apo-8-carotenoate/cadmium stearate mixed mono-layers in the highly condensed and easily transferable states. Surface pressure (P)—area (A) isotherm measurements on the mixed monolayers with varying compositions, showed that highly condensed monolayers can be formed at the air/water interface from mixtures containing as much as 20 mol % of the carotenoid dye. The mixed monolayers were successfully transferred onto the solid substrates as “Y-type” film by the vertical lifting method.     

Electrical transport and thermoelectric properties of Ca0.8Y0.2−xDyxMnO3−δ (0 ≤ x ≤ 0.2)

Ca_0.8Y_0.2?xDy_xMnO_3?δ (0≤x≤0.2) samples were fabricated by the solid‐state reaction method, and their thermoelectric properties were studied from 500°C to 800°C. Upon the substitution of Dy³⁺ for Y³⁺ in the Ca_0.8Y_0.2?xDy_xMnO_3?δ, the electrical and thermal conductivities gradually decreased with increasing Dy³⁺ concentration, whereas the absolute value of the Seebeck coefficient significantly increased. The Ca_0.8Dy_0.2MnO_3?δ showed the largest value of dimensionless figure of merit (0.180) at 800°C as a result of the combination of the largest absolute value of the Seebeck coefficient and the lowest thermal conductivity. We believe that the Ca_0.8Dy_0.2MnO_3?δ is a promising thermoelectric material at high temperatures.     

α‐Thiophene end‐capped styrene copolymer containing fullerene pendant moieties: Synthesis,characterization, and gas sensing properties

We report the synthesis, characterization, and gas sensing properties of a styrene copolymer bearing α‐thiophene end group and fullerene (C₆₀) pendant moieties P(S‐co‐CMS‐C₆₀). First, the copolymer of styrene (S) and chloromethylstyrene (CMS) monomers was prepared in bulk via a bimolecular nitroxide‐mediated radical polymerization (NMP) technique using benzoyl peroxide (BPO) as the radical initiator and nitroxy‐functional thiophene compound (Thi‐TEMPO) as the co‐radical and this gave α‐thiophene end‐capped copolymer P(S‐co‐CMS). The chloromethylstyrene units of P(S‐co‐CMS) allowed further side‐chain functionalization onto P(S‐co‐CMS). The obtained P(S‐co‐CMS) was then reacted with sodium azide (NaN₃) and this led to the copolymer with pendant azide groups, P(S‐co‐CMS‐N₃), and then grafted with electron‐acceptor C₆₀ via the reaction between N₃ and C₆₀. The final product was characterized by using NMR, FTIR, and UV–vis methods. Electrical characterization of P(S‐co‐CMS‐C₆₀) thin film was also investigated at between 30 and 100 °C as the ramps of 10 °C. Temperature dependent electrical characterization results showed that P(S‐co‐CMS‐C₆₀) thin film behaves like a semiconductor. Furthermore, P(S‐co‐CMS‐C₆₀) was employed as the sensing layer to investigate triethylamine (TEA), hydrogen (H₂), acetone, and ethanol sensing properties at 100 °C. The results revealed that P(S‐co‐CMS‐C₆₀) thin film has a sensing ability to H₂. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43641.     

Charge storage behavior of isotropic and biaxially‐oriented polypropylene films containing α‐ and β‐nucleating agents

A study on the influence of the crystal modification (α and β) of isotactic polypropylene (i‐PP) films on the resulting electret properties is presented. Two commercial nucleating agents, sodium 2,2′‐methylene‐bis(4,6‐di‐tert‐butylphenyl)‐phosphate (NA11) and N,N′‐dicyclo‐hexyl‐2,6‐naphthalene‐dicarbox‐amide (NU100), were employed in this investigation. Isothermal charge decay was measured at 90°C. In hot pressed isotropic polypropylene films, no significant differences in the charge storage properties were observed for α‐ and β‐nucleated specimens. In addition, the article presents the influence of the nucleating agents at different concentrations on the PP‐film morphology of biaxially stretched films with respect to electret features. It was possible to prepare elongated cavities with the virtually insoluble NA11 additive during stretching, even at concentrations below 0.3 wt %. These films displayed slightly improved electret properties in comparison to stretched neat PP films due to generated cavities acting as barriers for the drift of charges. Various draw ratios were also studied for i‐PP films with 0.15 wt % NA11. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 650–658, 2006     

Investigation of Sm2O3 additive on mechanical and electrical properties of Li2O‐ stabilized β″‐alumina electrolyte

Li₂O‐ stabilized β″‐alumina was synthesized by the double zeta process. The effect of Sm₂O₃ additive as the sintering aid, on microstructure, mechanical and electrical properties of Li₂O‐ stabilized β″‐alumina ceramics was studied by means of X‐ray diffraction, field emission scanning electron microscope, biaxial flexure test and ionic conductivity measurement. The results indicated that both the fracture strength and the ionic conductivity of the sample containing 0.2 wt% Sm₂O₃ improved approximately 52% and 54%, respectively, that can be attributed to its higher density, higher amount of β″‐Al₂O₃ phase and more uniform microstructure.     

High Na‐ion conducting Na1+x[SnxGe2−x(PO4)3] glass‐ceramic electrolytes: Structural and electrochemical impedance studies

Na‐ion conducting Na_1+x[Sn_xGe_2?x(PO₄)₃] (x = 0, 0.25, 0.5, and 0.75 mol%) glass samples with NASICON‐type phase were synthesized by the melt quenching method and glass‐ceramics were formed by heat treating the precursor glasses at their crystallization temperatures. XRD traces exhibit formation of most stable crystalline phase NaGe₂(PO₄)₃ (ICSD‐164019) with trigonal structure. Structural illustration of sodium germanium phosphate [NaGe₂(PO₄)₃] displays that each germanium is surrounded by 6 oxygen atom showing octahedral symmetry (GeO₆) and phosphorous with 4 oxygen atoms showing tetrahedral symmetry (PO₄). The highest bulk Na⁺ ion conductivities and lowest activation energy for conduction were achieved to be 8.39 × 10^?05 S/cm and 0.52 eV for the optimum substitution levels (x = 0.5 mol%, Na_1.5[Sn_0.5Ge_1.5(PO₄)₃]) of tetrahedral Ge⁴⁺ ions by Sn⁴⁺ on Na–Ge–P network. CV studies of the best conducting Na_1.5[Sn_0.5Ge_1.5(PO₄)₃] glass‐ceramic electrolyte possesses a wide electrochemical window of 6 V. The structural and EIS studies of these glass‐ceramic electrolyte samples were monitored in light of the substitution of Ge by its larger homologue Sn.     

On the Crystal Structure of the β′-Form of Triglycerides and Structural Changes at the Phase Transitions LIQ. → α → β′ ← β

Based on X-ray single crystal data of the β′-form of triundecanoin the general features of the molecular arrangement in this crystal form have been derived. The unit cell contains eight molecules arranged according to space group P2_1/c, with alternation of the tilt of the hydrocarbon chains in adjacent bimolecular layers. The structure within the molecular layer is quite similar to that of the β-form; the main difference being the chain packing. A second β″-form, β′₂, of triundecanoin has been observed and it differs from the one mentioned above in the orientation of the chain packing subcell 0° in relation to the true unit cell. The polymorphic transitions have been followed by recording of the diffraction pattern versus temperatures. The polymorphic transitions α · β′ · β can be regarded mainly as different lateral arrangement of a dimeric unit. In the α-form the chains are disordered near the methyl end groups, and due to this disorder the structure is closely related to the lamellar liquid-crystalline phase. It is also possible to classify β′-forms according to short-spacing data into a β′₁-type and a β′₂-type, and these groups can be identified also in complex triglycerides.     

Ruthenium(II)‐Catalyzed Protocol for Preparation of Diverse α,β‐ and β,β‐Dihaloenones from Diazodicarbonyls

Efficient one‐step syntheses of α,β‐ and β,β‐dihaloenones were achieved by ruthenium(II)‐catalyzed reactions between cyclic or acyclic diazodicarbonyl compounds and oxalyl chloride or oxalyl bromide in moderate to good yields. This methodology offers several significant advantages, which include ease of handling, mild reaction conditions, one‐step reaction, and the use of an effective and non‐toxic catalyst. The synthesized compounds were further transformed into highly functionalized novel molecules bearing aromatic rings on the enone moiety using the Suzuki reaction.

     

Fabrication and characteristics of graphene‐reinforced silver nanowire/polybenzoxazine/epoxy copolymer composite thin films

In this study, composite thin films were fabricated by mixing one‐dimensional silver nanowires (AgNWs) with graphene, polybenzoxazine (PBZ) and epoxy. Their electrical and thermal properties under different environmental conditions were investigated. The AgNWs were prepared by a polyol reduction method using ethylene glycol as a reducing agent and polyvinylpyrrolidone as a soft template to reduce silver ions. High aspect ratio AgNWs were then mixed into polymer matrices to allow them to form electrical and thermal conductive paths. Next, a trace amount of graphene was added into the nanocomposites in order to enhance their electrical and thermal properties. The results showed that the addition of graphene and AgNWs improved the threshold leakage current, and a 33% increase in thermal diffusivity was observed. The water resistance and gas barrier properties of PBZ and graphene effectively improved the thermal oxidation stability, and a 200% increase in electrical conductivity was achieved after 120 h of thermal oxidation treatment. A considerable difference was observed between the moduli of epoxy and PBZ. Hardness and phase analyses using atomic force microscopy showed that material modulus mismatch occurred across the interface between the materials, triggering phonon scattering. However, the increase in thermal conductivity was not significant for either material. © 2018 Society of Chemical Industry     

Preparation and properties of β‐phase graphene oxide/PVDF composite films

We report preparation of graphene oxide (GO) from expanded graphite (EG) via a modified Hummers method. GO/PVDF composites films were obtained using solvent N, N‐Dimethylformamide (DMF) and cosolvent comprising deionized water/DMF combination. X‐ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses revealed that the main crystal structure of the composite films is β‐phase, and use cosolvent method tends to favor the formation of β‐phase. Scanning electron microscopy (SEM) was used to investigate the microstructure of composite films. Storage modulus and loss modulus were measured by Dynamic mechanical analysis (DMA). Broadband dielectric spectrum tests showed an increase in the dielectric constant of the GO/PVDF composite films with the rising content of GO, and by cosolvent method could improve the dielectric constant while reducing the dielectric loss. Our method that uses GO as an additive and deionized water/DMF as the cosolvent provides a promising and low‐cost pathway to obtain high dielectric materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41577.     

Deacetylation of β‐chitin. II. Factorial experimental design

A 2³‐factorial experimental design has been used to study the main, two‐factor‐interaction, and three‐factor‐interaction effects of the NaOH concentration (X₁), deacetylation time (X₂), and deacetylation temperature (X₃) on the degree of deacetylation (DD) of deacetylated products prepared from β‐chitin. Because the DD values of deacetylated products increase as X₁, X₂, or X₃ increases, the main, two‐factor‐interaction, and three‐factor‐interaction effects for these three deacetylation conditions are positive. The sequence of the main effects on the DD values of deacetylated products is X₃ < X₂ < X₁. The sequence of the two‐factor‐interaction effects on the DD values of deacetylated products is X₂ versus X₃ < X₁ versus X₃ < X₁ versus X₂. The prediction equation is ? = 42.4 + 13.9X₁ + 9.4X₂ + 8.4X₃ + 5.8X₁X₂ + 4.9X₁X₃ + 3.7X₂X₃ + 2.6X₁X₂X₃ (where ? is the predicted response) © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2423–2428, 2004     

Effects of La content on the densification,microstructure, and conductivity of doped La10−xGe6O26±δ electrolytes

In this study, the influence of La content on the characteristics of Nb‐, Mo‐, and W‐doped La_xGe₆O_26±δ electrolytes was investigated through sintering study, X‐ray diffraction, scanning electron microscopy, and conductivity measurement. The densification of La_xGe_5.5Nb_0.5O_26±δ and La_xGe_5.5W_0.5O_26±δ was retarded as the x reached 9.75, while that of La_xGe_5.5Mo_0.5O_26±δ improved with increasing La content. The average grain size slightly increased and weight loss due to evaporation of GeO₂ significantly reduced with increasing La content, ranging from 1.39% to 0.26%. Among the systems studied, La_9.33Ge_5.5Nb_0.5O_26.245, La_9.33Ge_5.5Mo_0.5O_26.045, and La_9.50Ge_5.5W_0.5O_26.75 electrolytes revealed great potential for use in SOFC applications.     

Solution NMR Studies of Recombinant Aβ(1–42): From the Presence of a Micellar Entity to Residual β‐Sheet Structure in the Soluble Species

Amyloid‐β (Aβ) peptide is the major component found in senile plaques of Alzheimer's disease patients. The 42‐residue fragment Aβ(1–42) is proposed to be one of the most pathogenic species therein. Here, the soluble Aβ(1–42) species were analyzed by various liquid‐state NMR methods. Transient formation of a micelle species was observed at the onset of the aggregation kinetics. This micelle is dissolved after approximately one day. Subsequent loss of this species and the formation of protofibrils are proposed to be the route of fibril formation. Consequently, the observed micelle species is suggested to be on an off‐pathway mechanism. Furthermore, characterization of the NMR‐observable soluble species shows that it is a random‐coil‐like entity with low propensities for four β‐strands. These β‐strands correlate with the β‐strand segments observed in Aβ fibrils. This finding indicates that the 3D structure of the fibrils might already be predisposed in the soluble species.     

Structure, microstructure and electrical conductivity of 8YSZ containing NiO

The effects of NiO addition on the structure and microstructure of yttria-stabilized zirconia were investigated to clarify the role of the additive in the microstructure-related electrical conductivity of the solid electrolyte. Specimens of 8 mol% yttria-stabilized zirconia with NiO contents up to 5.0 mol% were prepared using nickel oxide and trihydroxi nickel carbonate as precursors. The specimens were sintered at 1350 °C for several holding times. The evolution of the lattice parameter with NiO content was evaluated by X-ray diffraction and the microstructural features by scanning electron microscopy. Electrical conductivity was evaluated by impedance spectroscopy measurements. The solubility limit of NiO at 1350 °C was found to be 1.5 mol% by X-ray diffraction. Energy dispersive spectroscopy results revealed Ni segregation for large holding times at 1350 °C. The grain boundary conductivity was found to be influenced by Ni segregation and to decrease with increasing holding times at high temperature.     

Functional monomers and polymers, 64. Synthesis of poly-β-alanine from β-alanine, β-alanyl-β-alanine,and β-alanyl-β-alanyl-β-alanine 4-dodecanoyl-2-nitrophenyl esters

Active 4-dodecanoyl-2-nitrophenyl esters of β-alanine, β-alanyl-β-alanine, and β-alanyl-β-alanyl-β-alanine were prepared, and tried to polymerize in various solvents. Nonpolar solvents were found to be convenient for the polycondensation reaction. The yield of the polycondensation was high for the monopeptide ester, and less for the dipeptide and tripeptide esters. The effect of temperature on the polycondensation reaction was also studied.     

Fabrication and properties of solution‐cast polyaniline/carboxymethylchitin blend films

Blend films consisting of polyaniline in emeraldine base form (PANI EB) dispersed in partially cross‐linked carboxymethylchitin (CM‐chitin) were prepared by solution casting, and characterized for their physical, thermal, and electrical properties. Homogeneous and mechanically robust blend films were obtained having PANI EB contents up to 50 wt % in the CM‐chitin matrix. FTIR spectra confirm intimate mixing of the two blend components. The thermal stability of the blend films increased with increase of PANI EB content, suggesting the formation of an intermolecular interaction, such as hydrogen bonding, between PANI EB and CM‐chitin chains. The addition of PANI EB into the pure CM‐chitin film resulted in a decrease in electrical conductivity of the films owing to disruption of ionic conduction of the CM‐chitin structure. After doping the blend films by immersion in HCl solution, the electrical conductivity of the HCl‐doped films increased with increase of the PANI EB content to a maximum value of the order of 10^?3 S/cm at 50 wt % PANI EB content. The electrical conductivity of the blend films was also dependent on the HCl concentration as well as on the type of acid dopant. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

YCrO3/Al2O3 Core‐Shell Design: The Effect of the Nanometric Al2O3‐Shell on Dielectric Properties

We report a novel strategy to improve the dielectric properties of the biferroic YCrO₃ ceramic compound through interface conduction control by means of an insulating Al₂O₃ using a core‐shell design. The YCrO₃ particles were covered with several layers of insulating Al₂O₃ using the atomic layer deposition technique to produce the core‐shell structure. TEM images reveal homogeneous and well‐defined Al₂O₃ coatings of ~8, ~60, and ~130 nm thickness. XRD shows the Al₂O₃‐shell to be amorphous. The dielectric characteristics of the sintered nano‐composite were investigated in the 100 Hz–1 MHz frequency range and temperature between 300 and 580 K. As the Al₂O₃‐shell thickness covering the YCrO₃ particles is increased, a decrease of the dielectric permittivity, loss tangent and AC conductivity values was found in the whole range of temperatures and frequencies. Furthermore, the rounded hysteresis loop, typical of conductive ceramic is restored as the insulating Al₂O₃ layer becomes thicker. This behavior is explained because the insulating Al₂O₃‐shell acts as internal barrier layer localizing the surface charges on the sintered grain boundaries. This fact was confirmed by Electron Beam Induced Current technique where a clear contrast at the grain boundaries confirms the charge localization at the YCrO₃/Al₂O₃ interface. These results also reveal that the Al₂O₃‐shell induces another conductive mechanism when the insulating Al₂O₃ layer becomes thicker. Nonetheless, this new strategy is an effective approach to suppress the parasitic conductivity in polycrystalline multiferroic ceramics and increasing thus the multifuncionality.     

Influence of two structural phases of Fe3O4 and γ‐Fe2O3 on the properties of polyimide/iron oxide composites

Partially aliphatic polyimide/iron oxide composites based on the poly(amic acid) from 5‐(2,5‐dioxotetrahydro‐3‐furyl)‐3‐methyl‐3‐cyclohexene‐1,2‐dicarboxylic acid anhydride and 4,4′‐oxydianiline with iron oxide in different weight percentages were obtained. The structural phases of the transition of magnetite to maghemite occurring in these composites, at different temperatures, are discussed. The physical characteristics, including magnetic, thermal, structural and morphological properties, evaluated using X‐ray diffraction, scanning electron microscopy and thermal analysis, are influenced by the interplay of the filler content and the structural changes of the composite. The X‐ray diffraction patterns of all samples show a cubic structure indexed as magnetite (Fe₃O₄) or maghemite (γ‐Fe₂O₃). Quantification of these two phases was evidenced by the Rietveld method. The electrical properties analysed under different humidity conditions evidence the potential applicability of these polyimide/iron oxide materials as humidity sensors. © 2015 Society of Chemical Industry     

Synthesis and growth mechanism of approximate spherical β‐Si3N4 particles via carbothermal reduction‐nitridation method

In this work, an efficient carbothermal reduction‐nitridation (CRN) strategy was rationally designed to directly synthesize β‐Si₃N₄ powders with eminent dispersity and granularity uniformity. With the aid of CaO additive, the obtained β‐Si₃N₄ particles were endowed with approximate spherical morphology and smooth surface. The size of β‐Si₃N₄ particles could be regulated in submicro and microscale by altering N₂ pressures. More significantly, the underlying growth mechanism of the β‐Si₃N₄ under elevated N₂ pressure was comprehensively analyzed and tentatively put forward. Benefiting from the remarkable merits, the as‐synthesized β‐Si₃N₄ powders showed great potential for alternative fillers in the application of high thermal conductivity plastic packages.     

High-yield γ-ray-induced polymerization of bis-2-acetoacetoxyethyl methacrylate copper. II.

The copper (II) acrylic monomer Cu(aaem)₂ (aaem = 2-acetoacetoxyethyl methacrylate) undergoes high-yield γ-ray copolymerization with dimethylacrylamide, styrene, and hydroxoethyl methacrylate in the presence of methylene bisacrylamide as crosslinking agent in dimethylformamide. The metalloorganic copolymers are fully characterized. Polymer-protected Cu(II) results in being extremely stable toward a number of reducing agents in different media. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2201–2207, 1997