Soybean oil-based thermoset reinforced with rosin-based monomer

A full bio-based cured resin was synthesized by copolymerization of acrylated-epoxidized soybean oil (AESO) and 2-acrylamidoethyl dehydroabietic acid (DHA-HEMAA). The rigid rosin-based monomer 2-acrylamidoethyl dehydroabietic acid was first prepared from dehydroabietic acid and N-hydroxyethylacrylamide, which was characterized by nuclear magnetic resonance and Fourier transform infrared (FTIR) spectrometry techniques. The cured resin was then synthesized and characterized by FTIR spectroscopy, differential scanning calorimetry, dynamic thermomechanical analysis, and thermogravimetric analysis, as well as using a Kruss tensiometer and a universal testing machine. The results indicated that the resin cured with rosin-based monomer exhibited excellent thermomechanical properties. The crosslink density and thermal stability of cured samples containing DHA-HEMAA at molar ratio between 10 and 30% were higher than those of AESO/DHA-HEMAA0 sample. With increasing DHA-HEMAA content, the glass transition temperature (T_g), elongation-at-break, and tensile strength of samples increased, in the stated order, from 16 to 38 °C, from 24 to 45.8%, and from 1.7 to 6.5 MPa. Due to DHA-HEMAA with a hydrophenanthrene structure, the θ values increased with the increase of DHA-HEMAA molar ratios. The full bio-based rosin thermosetting resins may have great potentials in practical application fields, such as coating, adhesive, and packaging materials.     

Preparation of epoxy-based insulator and optimization of its thermal property by Taguchi robust design method in double base propellant grain application

Taguchi method (orthogonal array, OA₉) was used to design an epoxy insulator by evaluating its glass transition temperature (T _g) for using in a double base (DB) propellant grain. In this design method, three epoxy resins based on diglycidylether bisphenol A (DGEBA), three polyamine curing agents and a DGEBA-based reactive diluent agent were used. The curing process of epoxy resins with polyamines was studied by Fourier transform infrared spectroscopy. The results showed that the curing process was completed at room temperature. The effects of four parameters including resin type, curing agent type, curing agent concentration and diluent quantity were investigated to design a resin formulation with a highest T _g after curing. The obtained results were quantitatively evaluated by the analysis of variance (ANOVA). The results of ANOVA showed that the highest T _g of 86.0 ± 9.0 °C was obtained for the optimum formulation of MANA POX-95 as epoxy resin, H-30 as curing agent and 52 phr H-30. The T _g measured by the experiment was 78.0 ± 0.9 °C. In addition, the single lap shear strength (adhesion strength) of the optimized insulator was measured at 13.66 ± 1.02 MPa. Pull-off test performed on the surface of DB propellant resulted a 1.935 ± 0.003 MPa adhesion strength.     

Structural Evolution of Silicon Carbide Phase from the Polycarbosilane Cured with Iodine: NMR Study

The structural evolution of silicon carbide phase from polycarbosilane fibers cured with iodine in air was investigated using nuclear magnetic resonance (NMR) together with in situ gas analysis up to 1400 °C by thermogravimetry coupled with mass spectroscopy (TG-MS). The investigation with solid-state ¹H, ¹³C, and ²⁹Si NMR analyses showed the influence of the oxygen affinity of Si atoms on the chemical structural changes of the SiOCH system during pyrolysis (up to 800 °C). In particular, the mechanism of phase segregation (SiOC?→?β-SiC?+?SiO₂?+?C) in amorphous SiOC structure at 800–1250 °C was determined. Carbon in the Si–O–C networks is replaced by silicon, forming the Si-O-Si network, while the cleaved carbon atoms, which have unpaired electrons, combine, forming C=C bonds. This mechanism accounts for the structural rearrangement from O₂SiC₂ to O₃SiC to SiO₄ (from the silicon-centered standpoint, i.e., SiO₂ phase), the growth of β-SiC crystallites, and the carbon clustering.     

Preparation of high surface area mesoporous nickel oxides and catalytic oxidation of toluene and formaldehyde

Mesoporous nickel oxide (NiO) nanoparticles were synthesized by the thermal decomposition reaction of Ni(NO₃)₂·9H₂O using oxalic acid dihydrate as the mesoporous template reagent. The pore structure of nanocrystals could be controlled by the precursor to oxalic acid dihydrate molar ratio, thermal decomposition temperature and thermal decomposition time. The structural characteristic and textural properties of resultant nickel oxide nanocrytals were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N₂ adsorption–desorption isotherm and temperature programmed reduction. The results showed that the most excellently mesoporous nickel oxide particles (m-Ni-1-4) with developed wormlike pores were prepared under the conditions of the mixed equimolar precursor and oxalic acid and calcined for 4 h at 400 °C. The specific surface area and pore volume of m-Ni-1-4 are 236 m² g^?1 and 0.42 cm³ g^?1, respectively. Over m-Ni-1-4 at space velocity = 20,000 mL g^?1 h^?1, the conversions of toluene and formaldehyde achieved 90 % at 242 and 160 °C, respectively. It is concluded that the reactant thermal decomposition with oxalic acid assist is a key step to improve the mesoporous quality of the nickel oxide materials, the developed mesoporous architecture, high surface area, low temperature reducibility and coexistence of multiple oxidation state nickel species for the excellent catalytic performance of m-Ni-1-4.     

Impedance sensor for the early failure diagnosis of organic coatings

A miniature impedance sensor used for field diagnosis of the early failure of coatings has been developed based on microelectronics and electrochemical impedance spectroscopy (EIS). The aging process of polyurethane-based coatings in salt spray test chamber was studied using the impedance sensor. Several critical indexes related to EIS such as phase angle (θ_10Hz, θ_15kHz), breakpoint frequency (f_b), specific capacitance (C_10Hz, C_15kHz), and impedance modulus (Z_0.1Hz) were proposed to evaluate the severity of coating degradation. The results indicated that the impedance sensor could accurately monitor the degradation process of coatings, and once Z_0.1Hz?<?10⁶ Ω cm², f_b?>?100 Hz, or θ_10Hz?<?20°, the coating may be regarded as completely degraded and fails to protect the metal substrate.     

Optimization of controlled ring-opening polymerization of <Emphasis Type="SmallCaps">l</Emphasis>-lactide to hydroxyl terminated polylactides using zinc acetate catalyst

Hydroxyl terminated polylactide polymers with number of average molecular weights (M _n ) varying from 1625 to 3459 g mol^?1 were synthesized by ring opening bulk polymerization of lactide in the presence of zinc acetate being a potent catalyst. The use of 1,4 butanediol (BDO) initiator leads to hydroxyl terminated polylactides, thus excellent precursors for shape-memory biodegradable polyurethanes. Different reaction conditions employed for the synthesis of hydroxyl terminated polylactide polymers via activated monomer mechanism may result in differences in M _n , percentage mass conversion and percentage degree of crystallinity (%χ _c ) of the product. Influence of process parameters, i.e. catalyst concentration, initiator concentration, reaction temperature and time on characteristics of hydroxyl terminated polylactides was studied. These polymers were characterized by Nuclear Magnetic Resonance (¹H-NMR) spectroscopy, Fourier transforms infrared (FTIR) spectroscopy, gel permeation chromatography (GPC) and X-ray diffraction (XRD) techniques. FTIR and ¹H-NMR confirmed the formation of hydroxyl terminated polylactides. M _n was determined by ¹H-NMR, GPC and end group analysis. %χ _c was calculated from XRD spectra. Maximum mass conversion, M _n and %χ _c were observed at 5 mol% SnOct₂ and 5 mol% BDO concentration. At optimum temperature of 145 °C, these characteristics improved linearly with polymerization time up to 6 h and declined thereafter.     

Novel amphiphilic temperature responsive graft copolymers PCL-<Emphasis Type="Italic">g</Emphasis>-P(MEO<Subscript>2</Subscript>MA-<Emphasis Type="Italic">co</Emphasis>-OEGMA) via a combination of ROP and ATRP: synthesis,characterization, and sol-gel transition

A series of well-defined novel amphiphilic temperature-responsive graft copolymers containing PCL analogues P(αClεCL-co-εCL) as the hydrophobic backbone, and the hydrophilic side-chain PEG analogues P(MEO₂MA-co-OEGMA), designated as P(αClεCL-co-εCL)-g-P(MEO₂MA-co-OEGMA) have been prepared via a combination of ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). The composition and structure of these copolymers were characterized by ¹H NMR and GPC analyses. The self-assembly behaviors of these amphiphilic graft copolymers were investigated by UV transmittance, a fluorescence probe method, dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses. The results showed that the graft copolymers exhibited the good solubility in water, and was given the low critical temperature (LCST) at 35(±1) °C, which closed to human physiological temperature. The critical micelle concentrations (CMC) of P(αClεCL-co-εCL)-g-P(MEO₂MA-co-OEGMA) in aqueous solution were investigated to be 2.0 × 10^?3, 9.1 × 10^?4 and 1.5 × 10^?3 mg·mL^?1, respectively. The copolymer could self-assemble into sphere-like aggregates in aqueous solution with diverse sizes when changing the environmental temperature. The vial inversion test demonstrated that the graft copolymers could trigger the sol-gel transition which also depended on the temperature.     

Curing kinetics of epoxy cured by cardanol-based phenalkamines synthesized from different polyethylenepolyamines by Mannich reaction

Phenalkamines with different structures are expected to affect the curing reaction of epoxy, yet the exact mechanism remains to be elucidated. In this study, four cardanol-based phenalkamines (named PK1, PK2, PK3, and PK4, respectively), synthesized from ethylenediamine, diethylenetriamine, triethylenetetramine, and pentaethylenehexamine, were used as curing agents in diglycidyl ether of bisphenol A (DGEBA) epoxy system. The phenalkamines were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, and time-of-flight secondary ion mass spectrometry. The curing behaviors and kinetics were investigated by non-isothermal differential scanning calorimetry, and the activation energies of the reactions (E _α ) were determined using Kissinger–Akahira–Sunose (KAS) and Starink methods. The results indicate a similar curing mechanism for all four phenalkamines. All E _α values remain almost constant in the range of 0.05 ≤ α ≤ 0.6, and increase dramatically after α > 0.6 due to greater viscosity of the reaction systems. The diffusion of reactive groups plays an increasingly important role in determining the curing kinetics. In addition, DGEBA/PK1 and DGEBA/PK2 have lower initial E _α values than DGEBA/PK3 and DGEBA/PK4, because PK1 and PK2 have lower viscosity than PK3 and PK4. When α is high, DGEBA/PK1 and DGEBA/PK2 have higher E _α values than DGEBA/PK3 and DGEBA/PK4, because more tertiary amine groups can be formed in the reactions between the epoxy and secondary amine groups in the DGEBA/PK3 and DGEBA/PK4 systems, which catalyze the curing reaction and it thus lowers energetic barrier.     

Synthesis and characterization of polyimides from 4,4′-(3-(<Emphasis Type="Italic">tert</Emphasis>-butyl)-4-aminophenoxy)diphenyl ether

A novel diamine 4,4′-(3-(tert-butyl)-4-aminophenoxy)diphenyl ether (4) was synthesized from 2-tert-butylaniline and 4,4′-oxydiphenol through iodination, acetyl protection, coupling reaction and deacetylation protection. Then some polyimides (PIs) were obtained by one-pot polycondensation of diamne 4 with several commercial aromatic dianhydrides respectively. They all exhibit enhanced solubility in organic solvents (such as NMP, DMF, THF and CHCl₃ etc.) at room temperature. Their number-average molecular weights are in the range of (2.1–3.7)?×?10⁴ g/mol with PDI from 2.25 to 2.74 by GPC. They can form transparent, tough and flexible films by solution-casting. The light transparency of them is higher than 90% in the visible light range from 400 nm to 760 nm and the cut-off wavelengths of UV–vis absorption are below 370 nm. They also display the outstanding thermal stability with the 5% weight loss temperature from 525 °C to 529 °C in nitrogen atmosphere. The glass transition temperatures (T _g s) are higher than 264 °C by DSC. XRD results demonstrate that these PIs are amorphous polymers with the lower water absorption (<0.66%). In summary, the incorporation of tert-butyl groups and multiple phenoxy units into the rigid PI backbones can endow them excellent solubility and transparency with relatively high T _g s.     

A Comprehensive Study on the Synthesis and Micellization of Disymmetric Gemini Imidazolium Surfactants

Two groups of disymmetric Gemini imidazolium surfactants, [C₁₄C₄C _m im]Br₂ (m = 10, 12, 14) and [C _m C₄C _n im]Br₂ (m + n = 24, m = 12, 14, 16, 18) surfactants, were synthesized and their structures were confirmed by ¹H NMR and ESI–MS spectroscopy. Their adsorption at the air/water interface, thermodynamic parameters and aggregation behavior were explored by means of surface tension, electrical conductivity and steady-state fluorescence. A series of surface activity parameters, including cmc, γ _cmc, π _cmc, pC ₂₀, cmc/C ₂₀, Γ _max and A _min, were obtained from surface tension measurements. The results revealed that the overall hydrophobic chain length (N _c) for [C₁₄C₄C _m im]Br₂ and the disymmetry (m/n) for [C _m C₄C _n im]Br₂ had a significant effect on the surface activity. The cmc values decreased with an increase of N _c or m/n. The thermodynamic parameters of micellization (ΔG _m ^θ , ΔH _m ^θ , ΔS _m ^θ ) derived from the electrical conductivity indicated that the micellization process of [C₁₄C₄C _m im]Br₂ and [C _m C₄C _n im]Br₂ was entropy-driven at different temperatures, but the contribution of ΔH _m ^θ to ΔG _m ^θ was enhanced by increasing N _c or m/n. The micropolarity and micellar aggregation number (N _agg) were estimated by steady-state fluorescence measurements. The results showed that the surfactant with higher N _c or m/n can form larger micelles, due to a tighter micellar structure.     

Atmospheric nitrogen loss factor (<Emphasis Type="Italic">f</Emphasis>) used in determining nitrogen-based municipal wastewater effluent irrigation rates: design and nitrogen-balance estimated <Emphasis Type="Italic">f</Emphasis> values

Design irrigation rates for treated municipal wastewater effluent (MWE) are usually determined from nitrogen (N) mass-balances, in which the fraction (f) of the total N in the MWE that is lost to the atmosphere is commonly obtained from US Environmental Protection Agency (USEPA) tabulated (design) values: 0.15–0.25 for secondary-treated effluents and 0.1 for tertiary-treated effluents. In 2011 and 2012, f values from an N balance in a tall fescue (Festuca arundinacea Schreb.) hay field in Central Pennsylvania were quantified and compared to the USEPA design f values. The grass field was spray-irrigated with MWE (C:N ratio = 0.04–0.2; near neutral pH, and 70–87% of the MWE-TN was NO₃–N) at a rate of ≤5-cm wk^?1. Monthly N balances were calculated from April to September in the surface horizon of a Hagerstown soil. The f values of 0.05, 0.1, and 0.2 seemed appropriate for the months of May and June, August and September, and July, respectively. Positive fnb estimates and the logarithm of measured monthly N removal in the aboveground biomass (kg ha^?1) were negatively correlated (R² = 0.99 for monthly mean air temperatures ≥20 °C and R² = 0.2 for monthly mean air temperatures <20 °C). The study’s results suggest that existing design f values are likely less applicable especially due to the biological N-removal processes currently present in many wastewater treatment plants needing to meet effluent N limits. Thus, more studies to determine empirical f values in effluent irrigation are needed to refine design f values.     

Production of MLM-Type Structured Lipids Catalyzed by Immobilized Heterologous <Emphasis Type="Italic">Rhizopus oryzae</Emphasis> Lipase

This work aims to produce triacylglycerols (TAG) containing a medium-chain fatty acid (M) at positions sn-1,3 and a long-chain fatty acid (L) at sn-2 position, i.e. TAG of MLM type, by acidolysis of virgin olive oil with caprylic (C8:0) or capric (C10:0) acids, catalyzed by 1,3-selective Rhizopus oryzae heterologous lipase (rROL) immobilized in Eupergit^® C and modified sepiolite. This lipase was produced by the methylotrophic yeast Pichia pastoris. Reactions were performed at 25 and 40 °C, for 24 h, either in solvent-free or in n-hexane media, at a molar ratio 1:2 (olive oil:free fatty acid). Higher incorporations of C8:0 (21.6 mol%) and C10:0 (34.8 mol%) into the TAG were attained in solvent-free media, at 40 °C, when rROL immobilized in Eupergit^® C was used. In organic media, at 40 °C, only 15.9 and 14.1 mol%, incorporation of C8:0 or C10:0 were, respectively observed. Lower incorporations were attained for both acids (3.4–7.0 mol%) when native ROL (nROL) in both supports and rROL in modified sepiolite were used. rROL in Eupergit^® C maintained its activity during the first four or three 23-h batches, respectively when C8:0 (half-life time, t _1/2 = 159 h) or C10:0 (t _1/2 = 136 h) were used, decreasing thereafter following a time delay model.     

Synthesis and Characterization of pH-Responsive Organic–Inorganic Hybrid Material with Excellent Catalytic Activity

Poly(N-isopropylmethacrylamide-co-methacrylic acid) [p(NipAam-Mac)] microgels were synthesized and used as microreactors to fabricate silver nanoparticles. Pure and hybrid microgels were characterized using Ultraviolet–Visible (UV/Vis) spectroscopy, Fourier transform infra-red (FTIR) spectroscopy and transmission electron microscopy (TEM). Catalytic activity of hybrid microgels and mechanism of catalysis by this system was explored using different reaction conditions. At the same temperature, apparent rate constant (k_app) was found to be varied from 0.0414 to 0.7852 min^?1 by increasing the concentration of NaBH₄ from 2.49 to 22.41 mM at constant concentration of substrate and catalyst. However upon extra increase in concentration of NaBH₄ from 22.41 to 37.35 mM reduced the value of k_app to 0.2178 min^?1. Likewise, the value of k_app was found to be increased from 0.1242 to 0.5495 min^?1 with increasing the concentration of 4-nitrophenol [Para-nitrophenol (p-Np)] from 0.063 to 0.079 mM keeping other parameters constant. Further increase in concentration of p-Np caused decline in the value of k_app. Kinetic data reveals that catalytic reduction of p-Np obeys Langmuir–Hinshelwood mechanism and p-Np is converted to p-Ap on the surface of the silver nanoparticles passing through various reaction intermediates.     

Second-Order NLO Active Heterotrimetallic Schiff Base Metallopolymer

The new ionic heterotrimetallic unsymmetrically-substituted Schiff base complex [Ni{(η ⁵-Cp)Fe(η ⁵-C₅H₄)-C(=O)CH=C(4-HO-C₆H₄)NCH₂CH₂N=CH-(2-O-(η ⁶-C₆H₄)Ru(η ⁵-Cp*)}][PF₆] (3; Cp = C₅H₅ and Cp* = C₅(CH₃)₅) was prepared in 86% yield by a one-pot procedure by mixing equimolar amounts of 4-hydroxyphenyl functionalized ferrocenylenaminone 1, the organometallic aldehyde [(η ⁵-Cp*)Ru(η ⁶-2-HO-C₆H₄CHO)][PF₆] (2) and nickel(II) acetate tetrahydrate in refluxing ethanol for 2 h. Its corresponding side-chain metallopolymer 4 was synthesized by reacting the organometallic-inorganic hybrid 3 with polyacrylic acid (DP = 25) in DMF at 110 °C for 48 h with an equimolar quantity of N,N′-dicyclohexylcarbodiimide and a catalytic amount of 4-dimethylaminopyridine. The new complex 3 was characterized by FT-IR and multidimensional NMR spectroscopy, elemental analysis and mass spectrometry. Single crystal X-ray diffraction analysis of 3 showed that the ferrocenyl and [(η ⁵-Cp*)Ru]⁺ units exhibit an anti-conformation and are almost coplanar with the unsymmetrical Schiff base complex fragment, while the 4-HO-C₆H₄ plane is almost perpendicular. The four-coordinate Ni^II metal ion adopts a square planar geometry, with two nitrogen and two oxygen donor atoms that are mutually trans. Size-Exclusion Chromatography established that metallopolymer 4 is formed of approximately three pendant ionic trimetallic units, while Differential Scanning Calorimetry and Thermal Gravimetric Analysis indicated that 3 and 4 are thermally stable with decomposition temperatures that exceed or border to 250 °C. Harmonic Light Scattering measurements at 1.91 µm incident wavelength showed that compounds 3 and 4 exhibit rather high second-order nonlinear responses, with hyperpolarizability β _1.91 values strongly increasing on passing from the monomeric unit 3 to its metallopolymeric counterpart 4.     

Synthesis,Characterization and Surface Properties of Amidosulfobetaine Surfactants Bearing Odd-Number Hydrophobic Tail

Three amidosulfobetaine surfactants were synthesized namely: 3-(N-pentadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2a); 3-(N-heptadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2b), and 3-(N-nonadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2c). These surfactants were prepared by direct amidation of commercially available fatty acids with 3-(dimethylamino)-1-propylamine and subsequent reaction with 1,3-propanesultone to obtain quaternary ammonium salts. The synthesized surfactants were characterized by IR, NMR and mass spectrometry. Thermogravimetric analysis (TGA) results showed that the synthesized surfactants have excellent thermal stability with no major thermal degradation below 300 °C. The critical micelle concentration (CMC) values of the surfactants 2a and 2b were found to be 2.2 × 10^?4 and 1.04 × 10^?4 mol/L, and the corresponding surface tension (γ_CMC) values were 33.14 and 34.89 mN m^?1, respectively. The surfactants exhibit excellent surface properties, which are comparable with conventional surfactants. The intrinsic viscosity of surfactant (2b) was studied at various temperatures and concentrations of multi-component brine solution. The plot of natural logarithm of relative viscosity versus surfactant concentration obtained from Higiro et al. model best fit the surfactant behavior. Due to good salt resistance, excellent surface properties and thermal stability, the synthesized surfactant has potential to be used in various oil field applications such as enhanced oil recovery, fracturing, acid diversion, and well stimulation.     

Cyanate ester resin modified by phenolic resin containing diphenyl oxide segments with high molecular weight

To obtain modified cyanate ester (CE) with good comprehensive properties and low cost, a novel phenolic resin containing diphenyl oxide (MPF) with high molecular weight was synthesized from diphenyl ether, formaldehyde, methanol and phenol by a two-step process which differed from polyphenylene oxide (PPO) in structure. The curing reaction and properties of the modified 2,2-bis(4-cyanatophenyl) propane (bisphenol-A-based cyanate ester, BADCy) by MPF were investigated. It was found that the curing temperature of the modified CE was lower than that of the unmodified CE. When the ratio of MPF and BADCy was 3:7, the cured resin exhibited low dielectric constant (3.00), low dielectric loss (0.0062) and high impact strength (12.5 kJ/m²), and its T _d5% was 371 °C, being superior to CE in the comprehensive properties. When the content of MPF was above 30 %, MPF/BADCy had poor comprehensive properties. In order to improve MPF/BADCy with high content of MPF, epoxy resin (E51) was added. When the ratio of MPF, BADCy and E51 was 50:50:67, the cured resin exhibited low dielectric constant (2.96), dielectric loss (0.0078) and high impact strength (11.84 kJ/m²), and its T _d5% was 365 °C. Small content of MPF or the combination of E51 and MPF were good for BADCy to improve its comprehensive properties.     

Synthesis,Characterization and Catalytic Activities of Palladium(II) Nitroaryl Complexes

Two palladium(II) nitroaryl complexes trans-[bromo(p-nitrophenyl)bis(triphenylphosphine)palladium(II)] 1 and trans-[bromo(2,4-dinitrophenyl)bis(triphenylphosphine)palladium(II)] 2 have been synthesized. The complexes were characterized by FTIR and NMR (¹H, ¹³C and ³¹P) spectroscopy and elemental analysis. The molecular structure of complex 2, as confirmed by X-ray crystallography, reveals that the Pd atom and its neighboring groups (two PPh₃, Br and phenylene group) lie in a slightly distorted square plane. In the UV–Vis spectra of the complexes 1 and 2, the palladium to aryl charge transfer bands were observed. The emission peaks from the singlet excited states (S₁ → S₀) were observed in the photoluminescence spectra of the complexes. The thermal stability of the complexes has been studied by thermal gravimetric analysis (TGA). TGA data showed that both complexes are thermally stable up to 200 °C, and complex 1 is more stable than 2. The catalytic efficiency of the new palladium(II) complexes was studied as demonstrated using the Sonogashira coupling reactions with good yields. The experimental results suggest that the Sonogashira coupling reactions can be performed at moderate temperature (50 °C) using these new palladium(II) complexes as catalysts.     

Seasonal N<Subscript>2</Subscript>O emissions respond differently to environmental and microbial factors after fertilization in wheat–maize agroecosystem

Biogeochemical processes regulating cropland soil nitrous oxide (N₂O) emissions are complex, and the controlling factors need to be better understood, especially for seasonal variation after fertilization. Seasonal patterns of N₂O emissions and abundances of archaeal ammonia monooxygenase (amoA), bacterial amoA, nitrate reductase (narG), nitrite reductase (nirS/nirK), and nitrous oxide reductase (nosZ) genes in long-term fertilized wheat–maize soils have been studied to understand the roles of microbes in N₂O emissions. The results showed that fertilization greatly stimulated N₂O emission with higher values in pig manure-treated soil (OM, 2.88 kg N ha^?1 year^?1) than in straw-returned (CRNPK, 0.79 kg N ha^?1 year^?1) and mineral fertilizer-treated (NPK, 0.90 kg N ha^?1 year^?1) soils. Most (52.2–88.9%) cumulative N₂O emissions occurred within 3 weeks after fertilization. Meanwhile, N₂O emissions within 3 weeks after fertilization showed a positive correlation with narG gene copy number and a negative correlation with soil NO₃^? contents. The abundances of narG and nosZ genes had larger direct effects (1.06) than ammonium oxidizers (0.42) on N₂O emissions according to partial least squares path modeling. Stepwise multiple regression also showed that log narG was a predictor variable for N₂O emissions. This study suggested that denitrification was the major process responsible for N₂O emissions within 3 weeks after fertilization. During the remaining period of crop growth, insufficient N substrate and low temperature became the primary limiting factors for N₂O emission according to the results of the regression models.     

Surface-initiated growth of copper using isonicotinic acid-functionalized aluminum oxide surfaces

Isonicotinate self-assembled monolayers (SAM) were prepared on alumina surfaces (A) using isonicotinic acid (iNA). These functionalized layers (iNA-A) were used for the seeded growth of copper films (Cu-iNA-A) by hydrazine hydrate-initiated electroless deposition. The films were characterized by scanning electron microscopy (SEM), electron-dispersive X-ray spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and advancing contact angle measurements. The films are Cu⁰ but with surface oxidation, and show a faceted morphology, which is more textured (R _q = 460 ± 90 nm) compared to the SAM (R _q = 2.8 ± 0.5 nm). In contrast, growth of copper films by SnCl₂/PdCl₂ catalyzed electroless deposition, using formaldehyde (CH₂O) as the reducing agent, shows a nodular morphology on top of a relatively smooth surface. No copper films are observed in the absence of the isonicotinate SAM. The binding of Cu²⁺ to the iNA is proposed to facilitate reduction to Cu⁰ and create the seed for subsequent growth. The films show good adhesion to the functionalized surface.