Ultrasonic velocity study of poly(R,R,4,4-cyclohexylidene diphenylene diphenyl ether-4,4-disulfonate) solutions at 30, 35 and 40 °C

Ultrasonic velocity (2 MHz) and acoustic parameters of poly(R,R^′-4,4^′-cyclohexylidene diphenylene diphenyl ether-4,4^′-disulfonate) (PS-1: RR^′H; PS-2: RCH₃ and R^′H; PS-4: RCH₃ and R^′Cl) solutions (chloroform, 1,2-dichloroethane and tetrahydrofuran (THF)) at 30, 35 and 40 °C have been determined to understand the effect of methyl and chlorine substituents on molecular interactions to support solvophilic or solvophobic nature of the polymers. The linear increase of U, Z, R, b, π, (α/f²)_Cl and τ with C and decrease of K_s, r, L_f and V_f with C suggested the existence of strong molecular interactions and hence solvophilic nature of the polymers, which is supported by positive values of S_n. A rise in temperature resulted in less ordered structure and more spacing between the molecules. The solvophilic nature of the polymers caused nonlinear variation of φ_v2 and φ_Ks with C and T. A powerful solvation exists in THF system. Structural modification is found above 2% for PS-2 and PS-4. The decrease of S_n with C and T indicated the presence of polymer-polymer interactions. The decrease of S_n with T is due to disruption of the structure formed by predominant thermal energy over molecular interaction energy.     

Retention profile, kinetics and sequential determination of selenium(IV) and (VI) employing 4,4'-dichlorodithizone immobilized-polyurethane foams

Polyurethane foams (PUFs) loaded with the chromogenic reagent 4,4′-dichlorodithizone (Cl₂H₂D_Z) have been investigated for the quantitative retention, chemical speciation and sequential determination of traces of inorganic selenium(IV) and (VI) from aqueous media containing bromide ions. The retention profile of selenium(IV) onto the reagent loaded foam followed a dual-mode sorption mechanism involving both absorption related to “solvent extraction” and an added component for surface adsorption. The kinetics and thermodynamic characteristics of selenium(IV) uptake onto PUFs have been studied. The kinetics of selenium(IV) sorption onto PUFs was found fast, reached equilibrium in few minutes and followed a first-order rate constant in presence of bromide ions in the extraction media. The thermodynamic parameters, ΔH, ΔS and ΔG, indicated the exothermic and spontaneous nature of the sorption process. The sorption and the recovery percentages of inorganic selenium(IV) from fresh water by the proposed loaded foam columns were achieved quantitatively. The height equivalent to theoretical plate (HETP), the number of layers (N), breakthrough capacity and the critical capacity for selenium(IV) uptake onto Cl₂H₂D_Z loaded foams columns were found to be 1.3, 103, 8.6 and 7.2 mg/g, respectively. The method was successfully applied for the chemical speciation and sequential determination of inorganic selenium(IV) and/or (VI) species spiked to fresh and industrial wastewaters.     

Synthesis and Properties of Melt Processed Poly（thiourea-azo- sulfone）/Carbon Nanotubes Nanocomposites

An aromatic azo-polymer, poly(thiourea-azo-sulfone)(PTAS), has been prepared using 4-(4-aminophenylsulfonyl)benzenamine and diazonium salt solution of 2,6-diaminopyridine. PTAS was easily processable using polar solvents and had high molar mass 63 × 103g mol 1according to GPC. Mechanically and thermally stable and electrically conducting polymer/CNTs nano-composites were obtained via melt processing technique. Fine distribution of CNTs in a polymer matrix performed an essential role in the preparation of polymer/CNTs nano-composites based on interfacial interaction between CNTs and polymer matrix. Scanning electron micrographs showed good dispersion of filler and adhesion of matrix on the surface of nanotubes. Accordingly, increasing the amount of CNTs from 0.1 wt% to 5 wt% increased the electrical conductivity from 2.99 S cm 1to 3.56 S cm 1. Mechanical strength of functional nanotubes-based hybrids was enhanced from 43.22 MPa to 65.02 MPa compared with that of hybrids with non-functional filler in matrix 37.21 MPa. A rapport between nanotube loading and thermal stability of the materials was also observed. 10% gravimetric loss temperature was increased from 528 °C to 578 °C, while glass transition was improved from 241 °C to 271 °C. Adding up of small quantity of functional CNTs strongly affected the tensile, electrical and thermal properties of materials. Improvement of the physical properties of CNT-reinforced polymer nano-composites was ascribed to the melt processing technique.     

Synthesis, structure and physical properties of LnNi(Sn,Sb)3 (Ln=Pr, Nd, Sm, Gd, Tb)

Five new analogues of the β-CeNiSb₃ family have been synthesized and found to be LnNi(Sn,Sb)₃ and isostructural to the previously reported β-CeNiSb₃. LnNi(Sn,Sb)₃ (Ln=Pr, Nd, Sm, Gd, or Tb) crystallizes in the orthorhombic space group, Pbcm, with lattice parameters of a∼12.9 Å, b∼6.1 Å, c∼12.0 Å. The structure consists of layers of nearly square nets of X (X=Sn/Sb) atoms and highly distorted NiX₆ octahedra. Lanthanide atoms are located between layers of X and NiX₆ octahedra. All analogues are metallic and experimental effective magnetic moments are in agreement with the respective Ln³⁺ calculated moments.     

Complexation between poly(N,N-diethylacrylamide) and poly(acrylic acid) in aqueous solution

The complexation between poly(N,N-diethylacrylamide) (PDEA) and poly(acrylic acid) (PAA) in aqueous solution was studied by viscometric, potentiometric, and fluorescence techniques. It was found that an interpolymer complex formed between the two polymers through hydrogen bonding interactions with the stoichiometry of r=0.6 (r is unit molar ratio of PAA/PDEA), and the complex formation show the dependence on pH values. The phase behaviour studies showed that the lower critical solution temperature of the PDEA-PAA aqueous solution gradually increased with the increasing of r from 0.01 to 0.15, until a soluble system in the whole temperature region was obtained, which remained in the range of r=0.15-0.3. At higher PAA concentrations, when r is above 0.3, the system appeared phase separation, and almost no temperature dependence was observed. Based on these conclusion and structure characteristics of PDEA and PAA, a model containing only short sequences of monomer residues was proposed for the structure of PDEA-PAA complex.     

Mechanical and thermal properties of nanosized titanium dioxide filled rigid poly(vinyl chloride)

Nano-sized rod-like titanium dioxide (TiO2) filled rigid poly(vinyl chloride) (PVC) nanocomposites were prepared by using injection-molding method. Vicat, Charpy impact and tensile tests as well as thermogravimetric and dynamic mechanical analyses were used to characterize the structure and properties of the nanocomposites. The results showed that nano-TiO2 could improve Vicat softening temperature and also improve thermal stability of PVC during the stages of dehydrochlorination and formation of carbonaceous conjugated polyene sequences, which can be ascribed to restriction of the nanoparticles on the segmental relaxation as being evidenced by raises in glass transition and β-relaxation temperatures of PVC upon filling TiO2. Addition of TiO2 nanoparticles less than 40 phr (parts per hundreds of resin) could significantly improve impact strength of the composites while the TiO2 agglomeration at high contents leads to a reduction in impact toughness.     

Thermal properties and degradability of poly(propylene carbonate)/poly(β-hydroxybutyrate-co-β-hydroxyvalerate) (PPC/PHBV) blends

Poly(propylene carbonate)/poly(β-hydroxybutyrate-co-β-hydroxyvalerate) (PPC/PHBV) blends were prepared via the solution casting method at different proportions. Their thermal characteristics were studied by means of differential scanning calorimetry (DSC) and thermogravimetry (TG). The degradability of the blends was investigated in soil suspension cultivation and in vitro degradation testing. The changes of structure and molecular weight for blends were also studied by ¹H nuclear magnetic resonance spectroscopy (¹H NMR), scanning electron microscopy (SEM) and gel permeation chromatography (GPC) before and after degradation. Although the PPC/PHBV blends were immiscible, the addition of PHBV could improve the thermal stability of PPC. PHBV was degraded mainly by the action of microbial enzymes in the soil suspension, which biodegraded it more rapidly than PPC in a natural environment. PPC was degraded mainly by chemical hydrolysis and random hydrolytic scission of chains in the PBS solution in vitro, and degradation of PPC was more rapid than that of PHBV in a simulated physiological environment.     

Characterization and properties of biodegradable poly(hydroxyalkanoates) and 4,4-dihydroxydiphenylpropane blends: Intermolecular hydrogen bonds, miscibility and crystallization

Intermolecular hydrogen bonds, miscibility, crystallization and thermal stability of the blends of biodegradable poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-3HHx)] with 4,4-dihydroxydiphenylpropane (DOH₂) were investigated by FTIR, ¹³C solid state NMR, DSC, WAXD and TGA. Intermolecular hydrogen bonds were found in both blend systems, which resulted from the carbonyl groups in the amorphous phase of both polyesters and the hydroxyl groups of DOH₂. The intermolecular interaction between P(3HB-3HHx) and DOH₂ is weaker than that between PHB and DOH₂ owing to the steric hindrance of longer 3HHx side chains. Because of the effect of the hydrogen bonds, the chain mobility of both PHB and P(3HB-3HHx) components was limited after blending with DOH₂ molecules. Single glass transition temperature depending on the composition was observed in all blends, indicating that those blends were miscible in the melt. The addition of DOH₂ suppressed the crystallization of PHB and P(3HB-3HHx) components. Moreover, the crystallinity of PHB and P(3HB-3HHx) components also decreased with increasing DOH₂ content in the blends. However, the crystal structures of the crystallizable components were not affected. The existence of DOH₂ favors to thermal decomposition of PHB and P(3HB-3HHx) components, resulting in the decrease in thermal decomposition temperature.     

Synthesis and hybridization affinity of oligodeoxyribonucleotides incorporating 4-N-(N-arylcarbamoyl)deoxycytidine derivatives

Modified oligodeoxynucleotides incorporating 4-N-(N-arylcarbamoyl)-dC derivatives 1a-c were synthesized. The ¹H NMR spectra of 1a-c suggest that the carbamoyl group forms an intramolecular hydrogen bond with the cytosine ring nitrogen atom so that formation of a Watson-Crick base pair with the complementary guanine base is inhibited. The hybridization properties of oligodeoxynucleotides containing 1a-c were investigated by use of T_m analysis. The hybridization properties of 4-N-(N-phenylcarbamoyl)-dC (1a) were similar to those of 4-N-(N-alkylcarbamoyl)-dC derivatives reported previously. In sharp contrast to 1a, it turned out that 4-N-(N-napht-1-yl) and (N-quionol-5-yl)-dC (1b,c) have a unique property as a universal base.     

Crystal growth, transport, and magnetic properties of Ln3Co4Sn13 (Ln=La, Ce) with a perovskite-like structure

Ln₃Co₄Sn₁₃ (Ln=La, Ce) have been synthesized by flux growth and characterized by single crystal X-ray diffraction. These compounds adopt the Yb₃Rh₄Sn₁₃-type structure and crystallize in the cubic space group (No. 223) with Z=2. Lattice parameters at 298 K are , , and , for the La and Ce analogues, respectively. The crystal structure consists of an Sn-centered icosahedron at the origin of the unit cell, which shares faces with eight Co trigonal prisms and 12 Ln-centered cuboctahedra. Magnetization data at 0.1 T show paramagnetic behavior down to 1.8 K for Ce₃Co₄Sn₁₃, with per Ce³⁺, while conventional type II superconductivity appears below 2.85 K in the La compound. Electrical resistivity and specific heat data for the La compound show a corresponding sharp superconducting transition at T_c∼2.85 K. The entropy and resistivity data for Ce₃Co₄Sn₁₃ show the existence of the Kondo effect with a complicated semiconducting-like behavior in the resistivity data. In addition, a large enhanced specific heat coefficient at low T with a low magnetic transition temperature suggests a heavy-fermionic character for the Ce compound. Herein, the structure and physical properties of Ln₃Co₄Sn₁₃ (Ln=La, Ce) are discussed.     

Synthesis of 1-fluoroindan-1-carboxylic acid (FICA) and its properties as a chiral derivatizing agent

1-Fluoroindan-1-carboxylic acid (FICA) (1) was designed and synthesized as its methyl ester (FICA Me ester) (4) in order to develop an efficient chiral derivatizing agent (CDA) which excels α-methoxy-α-(trifluoromethyl)phenylacetic acid (MTPA) in capability. FICA Me ester (4) was prepared by fluorination of methyl 1-hydroxyindan-1-carboxylate (3) with (diethylamino)sulfur trifluoride (DAST) and derived to the esters of racemic secondary alcohols by ester exchange reaction. The resulting Δδ_F value was large in the case of 2-butyl ester of FICA (5a), whereas not detectable in the case of the corresponding MTPA ester (6a). The magnitude of the Δδ_H values was similar to that of MTPA esters. The diastereomers of (R)-(−)-8-phenylmenthyl ester of FICA (5i) was separated and their ¹H NMR analyses revealed that the concept of the modified Mosher's method was successfully applied to 5i.     

Concise Stereoselective Total Synthesis of (4R, 6R)-Lactone Moiety Analog of Mevinoline and Compactin

A simple and highly efficient synthetic route has been developed for analogue of HMGCo A reductase inhibitor (1). The strategy utilizes S-Corey–Bakshi–Shibata (CBS) reduction, FeCl₃-catalyzed C-H insertion of ethyl diazoacetate.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.]     

Synthesis and magnetic properties of rare earth ruthenates, Ln5Ru2O12 (Ln=Pr, Nd, Sm-Tb)

Single crystals of Ln₅Ru₂O₁₂ (Ln=Pr, Nd, Sm-Tb) were grown out of either NaOH or KOH fluxes in sealed silver tubes. The crystals of all the phases were observed to be twinned as confirmed by TEM studies. The series crystallize in the C2/m monoclinic system with lattice parameters, a=12.4049(4)-12.7621(6) Å, b=5.8414(2)-5.9488(3) Å, c=7.3489(2)-7.6424(4) Å, β=107.425(3)-107.432(2)° and Z=2. The crystal structure is isotypic with the defect/disorder model of Ln₅Re₂O₁₂ (Ln = Y, Gd) and consists of one dimensional edge shared RuO₆ octahedral chains separated by a two dimensional LnO_x polyhedral framework. Magnetic measurements indicate paramagnetic and antiferromagnetic behavior for Ln=Nd, Sm-Gd and Ln=Tb, respectively.     

Synthesis and properties of poly(aniline-co-azidoaniline)

Copolymers of polyaniline and o-azidoaniline were synthesized by chemical oxidative polymerization. The copolymers were characterized by powder X-ray diffraction (XRD) and UV/Vis and FT-IR spectroscopy. Thermal activation of the azido chromophore in the copolymer caused it to react and cross-link into adjacent polymer chains. The cross-linking of the copolymers was indicated by the depletion of the azido band in the FT-IR spectrum. The effects of the cross-linking were studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and four-probe conductivity. The TGA showed that the thermal stability of the copolymers is improved due to cross-linking. However, the increased thermal stability is accompanied by a decrease in electrical conductivity due to the loss of conjugation detected by UV/Vis spectroscopy and a loss of crystallinity due to the azido substituents, which was demonstrated by XRD.     

Paper-based solid-state electrochemiluminescence sensor using poly(sodium 4-styrenesulfonate) functionalized graphene/nafion composite film

Herein, highly efficient solid-state ECL sensor was introduced for the first time onto the screen printed electrodes of the paper-based chips (PCs) based on the composite film of poly(sodium 4-styrenesulfonate) functionalized graphene (PSSG) and Nafion. Attributed to the cooperative characteristics of both PSS and graphene, PSSG ensured both effective Ru(bpy)₃²⁺ immobilization and fast electron transfer of Ru(bpy)₃²⁺ in the composite film. The ECL behaviors at the developed sensor were investigated using tripropylamine as a representative analyte and low detection limit (S N⁻¹ = 3) of 5.0 nM was obtained. It also exhibited more excellent reproducibility (relative standard deviations of 0.63% for continuous 45 cycles) and long-term stability (∼80% of its initial ECL intensity could be retained over 3 months). More importantly, assisted by the developed ECL sensor, discrimination of 1.0 nM single-nucleotide mismatch in human urine matrix could be realized on the PCs for the first attempt. Thus, the developed sensor was confirmed with the advantages of highly sensitivity, long-term stability, simplicity, low cost, disposability, high efficiency and potential applicability.     

Water-soluble poly(2-(3thienyloxy)ethanesulfonic acid)/V2O5 nanocomposites: synthesis and electrochromic properties

Water-soluble conducting poly(2-(3thienyloxy)ethanesulfonic acid) (PTOESA)/V₂O₅ nanocomposite, (PTOESA)_xV₂O₅, was prepared by simply mixing PTOESA with V₂O₅ wet gel at room temperature. XRD data showed that the interlayer spacings of (PTOESA)_xV₂O₅ films are 14.0±1.5 Å and increased as the polymer content increased. These values are consistent with the insertion of polythiophene chains into the V₂O₅ layer gallery. The formation of alternative layers of PTOESA and V₂O₅ was further supported by depth profile SIMS analyses. Cyclic voltammograms of (PTOESA)_xV₂O₅ film showed two pairs of redox peaks with colors varying from orange, yellowish green, green, to purple blue, depending on the stoichiometry of the nanocomposites. Moreover, a synergetic effect was observed on the electrochromic properties of these nanocomposites. It was found that the optical contrast (ΔOD) of the composites is better than those of PTOESA and V₂O₅ at the film thickness from 150 to 500 nm. The oxidation optical response time of (PTOESA)_xV₂O₅ is independent of the stoichiometry and falls in between those of PTOESA and V₂O₅. At higher polymer content (x>0.5), the reduction optical response time of (PTOESA)_xV₂O₅ is smaller than those of PTOESA and V₂O₅. Variable temperature conductivity data showed that the conductivity of (PTOESA)_xV₂O₅ films increased as temperature increased, characteristic of thermal activated behavior, which was dominated by the interparticle contact resistance. The room-temperature conductivity of water-soluble (PTOESA)_xV₂O₅ films was in between those of PTOESA and V₂O₅ xerogel and higher conductivity was found in the composite with lower polymer content. The anomalous conductivity of (PTOESA)_xV₂O₅ with high PTOESA content may be due to the reason that the higher the polymer content, the bigger the grain size of (PTOESA)_xV₂O₅ film as revealed with scanning electron microscopy and AFM micrographs.     

Hydrothermal synthesis and magnetic properties of RMn2O5 (R=La, Pr, Nd, Tb, Bi) and LaMn2O5+δ

RMn₂O₅ (R=La, Pr, Nd, Tb, Bi) crystallites were prepared by a mild hydrothermal method and characterized by powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and magnetic measurement. The formation of manganates was sensitive to the alkalinities and Mn-containing precursors of the reaction mixtures. This family of manganates is isostructural and has a space group of Pbam. The magnetic measurements for RMn₂O₅ showed an antiferromagnetic transition. The strong irreversibility between the ZFC and FC curves indicated a helicoidally magnetic structure below 40 K. The max d.c. susceptibilities of LaMn₂O_5+δ (δ=0.01, 0.06, 0.08, 0.16, 0.17) were found to be variable and the excess oxygen (δ) in the compounds was influenced by the alkalinity used in the hydrothermal synthesis.     

Crystal growth of Ln3GaO6 (Ln = Nd, Sm, Eu and Gd): Structural and optical properties

Single crystals of Ln₃GaO₆ (Ln = Nd, Sm, Eu, Gd) were grown out of a reactive high temperature hydroxide melt. The structures were solved by single-crystal X-ray diffraction. These gallium oxides crystallize in the polar space group Cmc2₁ where the orientation of the GaO₄ tetrahedra determines the polarity of the structure. The atomic positions along with the determination of the absolute structure are reported. The lanthanide atoms are located in a seven-fold coordination environment forming edge-sharing zigzag-chains. The photoluminescence was investigated and the europium and gadolinium members of this series exhibit intense luminescence in the visible portion of the spectrum.     

Enantioselective Total Synthesis of (R,R)-Blumenol B and d9-(R,R)-Blumenol B

C₁₃-norisoprenoids are of particular importance to grapes and wines, as these molecules influence wine aroma and have been shown to significantly contribute to the distinct character of various wine varieties. Blumenol B is a putative precursor to a number of important wine aroma compounds, including the well-known compounds theaspirone and vitispirane. The enantioselective synthesis of (R,R)-blumenol B from commercially available 4-oxoisophorone was achieved using a short and easily scaleable route, which was then successfully applied to the synthesis of poly-deuterated d9-blumenol B.