Amorphous polyamide coating resins from sugar-derived monomers

In this article, the synthesis of bio-based polyamides for powder coating applications and their evaluation in a solventborne coating system are reported. The M _n values of the resins were between 3000 and 4000 g mol^?1 and the resins displayed T _g values from 60 to 80°C. Both amine and carboxylic acid functionalities (total ~0.6 mmol g^?1) were introduced for curing purposes. The resins were cured with triglycidyl isocyanurate (TGIC) or N,N,N′,N′-tetrakis(2-hydroxyethyl)adipamide (Primid XL-552). The curing reaction was followed using rheology which indicated that TGIC achieved higher reaction rates and higher gel contents. The DSC analysis of the cured disks showed that all cured samples were amorphous as is desired for the targeted coating application. The resins required a curing temperature higher than 150°C. Aluminum panels were coated using a solventborne approach and the coatings were cured at 180°C during 1 h. Dewetting was observed on all panels. Network formation was adequate for an amine-functional resin cured with TGIC as indicated by solvent resistance testing. In conclusion, the developed bio-based polyamide resins are promising materials to be used as binder resins in powder coating applications.     

Solvent-induced crystallization of electrospun syndiotactic polystyrene nanofibers and its reversible desorption/sorption of volatile organic vapors

Electrospun fiber mats are promising media for chemical separation because of their porous interior and high surface area, which enhance penetrant permeation and provide a large number of active sites. The application of this technology was fulfilled in the present study, wherein syndiotactic polystyrene (sPS) fibers were prepared by high-temperature solution electrospinning to absorb volatile organic compounds. The as-spun sPS fibers had an average radius of ~360 nm and were amorphous as revealed by Fourier transform infrared spectroscopy (FTIR) and wide-angle X-ray diffraction. When the electrospun fibers were exposed to different solvent vapors, solvent-induced crystallization occurred in these submicron-sized fibers to form δ- or γ-form sPS crystals, depending on the solvent used. To trace the microstructure transformation of sPS chains induced by the solvent vapors, in situ FTIR spectral measurements were performed. The absorbance of crystallization-sensitive IR bands was plotted against time, from which the crystallization kinetics were analyzed based on the Avrami equation. Results showed that the rate of solvent-induced crystallization was higher for solvents with a higher saturated vapor pressure. Subsequent solvent desorption from the crystallized sPS fibers was also studied under ambient conditions by monitoring the absorbance variation of the solvent-sensitive IR band. Two-stage solvent desorption was observed in the δ-form sPS fibers; this process consisted of initial rapid desorption from the amorphous region, followed by slow desorption from the crystalline region. Notably, all the solvent molecules in the treated fibers can be completely removed in this manner, thereby leading to the formation of δ _e-form crystals for repetitive sorption/desorption applications.     

Synthesis and characterization of BEC-zeotype germanosilicates and B-substituted zeolitic materials

Pure BEC-type germanosilicates (denoted as SiGe-BEC) and B-containing BEC-zeotype (denoted as B-BEC) materials were synthesized by the hydrothermal method in the presence of an organic structure-directing agent, N,N,N′,N′-Tetra-methylethylenediamine. The effects of the reaction mixture ratio and the incorporation of transition boron on the synthesis of the pure product were investigated. The synthesized samples were characterized by powder and single-crystal X-ray diffraction, scanning electron microscopy, inductively coupled plasma analysis, thermogravimetric analysis, and nitrogen sorption measurements. The results reveal that the crystallization time, the concentration of H₂O in the reaction mixture and the addition of HF have an important impact on the synthesis of BEC-type zeolite. It was also determined that Ge atoms occupy only the T sites in the D4Rs units. BEC material in the germanosilicate form is stable up to 800 °C and boron can successfully be introduced into the BEC-type (denoted as B-BEC) framework.     

Interpreting the pH-dependent mechanism of simazine sorption to <Emphasis Type="Italic">Miscanthus</Emphasis> biochar produced at different pyrolysis temperatures for its application to soil

Biochar has received considerable attention as an eco-friendly bio-sorbent; however, multifarious characteristics caused by pyrolysis and feedstock pose difficulties in its application. We characterized the pH-dependent sorption of the pesticide simazine on Miscanthus biochar produced at two pyrolysis temperatures (400 and 700 °C; hereafter B-400 and B-700). The specific surface-area (SSA) of the micro- and nanopores, elemental composition, surface acidity and infrared spectra were determined. The SSA was greater in B-700 than in B-400, and the former had greater SSA in micro-pores and lower SSA in nanopores than the latter. During pyrolysis, the single-bond structures of the feedstock were converted to aromatic structures, and further pyrolysis led to ligneous structures. Alterations in pore structure and concave-up Scatchard plot corroborated the presence of two sorption mechanisms: electrostatic attractions (S_es) and hydrophobic attractions (S_hp). Decreases in maximum sorption in the q_max-L with increasing pH was due to decreased S_es via deprotonation of carboxylic groups on biochar, while those in the q_max-H with increasing pyrolysis temperature were due to decreased S_hp, resulting from pore structure deformation. We believe that our approach, which addresses the pH-dependence of charge density of sorbate and sorbent, could contribute to a better understanding of the behavior of simazine.     

Cure kinetics of cyanate ester resin using microencapsulated dibutyltin dilaurate as catalyst

Dibutyltin dilaurate (DBTDL) catalyst-filled microcapsules (MCs) were used to catalyze the reaction of thermosetting cyanate ester (CE) resins. Dynamic differential scanning calorimetry (DSC) experiments were performed at multiple heating rates (β) to investigate the effects of the MC content (0.125, 0.25, and 0.5 %) on the cure kinetics of CE resins. The kinetic parameters of CE/MC systems, including activation energy (E _a), preexponential factor (A), and reaction order (n), were analyzed using the Flynn–Wall–Ozawa method, Kissinger method, Crane method, Ozawa isoconversional method, and Coats–Redfern method. The results indicate that, as the MC content increases, the reaction temperature of CE/MC system gradually shifts to low temperature owing to the increase of the DBTDL catalyst released from MCs under heating conditions. Compared to the unencapsulated DBTDL, the encapsulated DBTDL can decrease the E _a, A, and the reaction rate constant of CE resins due to the gradual release of DBTDL from MCs and the homogeneous dispersion of the released DBTDL in CE resins. The E _a, A, and the reaction rate constant of CE/MC systems are effectively adjusted by the MC content and heating process. The reaction orders for all CE/MC systems are close to 1. The reaction model of CE/MCs is considered as a two-dimensional nucleation (A ₂).     

Oxidation of ash-free coal from sub-bituminous and bituminous coals in a direct carbon fuel cell

The present study proposes the production of ash-free coal (AFC) and its oxidation as a primary fuel in direct carbon fuel cells (DCFCs). The AFC was produced by the extraction of Arutmin sub-bituminous coal (AFC1) and Berau bituminous coal (AFC2) using polar solvents such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). It was carried out at a temperature of around 202 °C under atmospheric conditions and using a microwave irradiation method. Using NMP as the solvent showed the highest extraction yield, and the values of 23.53% for Arutmin coal and 33.80% for Berau coal were obtained. When NMP was added to DMSO, DMA and DMF, the extraction yield in the solvents was greatly increased. The yield of AFC from a sub-bituminous coal was slightly lower than that from a bituminous coal. The AFC was evaluated in a coin-type DCFC with a mixture of AFC and carbonate electrolyte (3 g/3 g) at 850 °C. The AFC and gaseous H₂ fuels were compared using the electrochemical methods of steady-state polarisation and step chronopotentiometry. The DCFC ran successfully with the AFCs at 850 °C. The open-circuit voltages were about 1.35 V (AFC1) and 1.27 V (AFC2), and the voltages at 150 mA cm^?2 were 0.61 V (AFC1) and 0.74 V (AFC2).     

General trends in concentration and temperature behavior of equivalent conductance of <Emphasis Type="Italic">N,N</Emphasis>-diallylammonium polymers aqueous solutions: Effect of counterion nature and amine structure

The specific and equivalent conductivity of the diluted aqueous solutions of diallyammonium polyelectrolytes, initial monomers (N,N-diallylammonium trifluoroacetate, N,N-diallyl-N-methylammonium trifluoroacetate, N,N-diallyl-N,N-dimethylammonium chloride), and also potassium trifluoroacetate and trifluoroacetic acid solutions are studied. The limiting ionic mobility of diallylammonium cations and trifluoroacetate anion are found. The regularities of concentration changes in the equivalent conductance of polyelectolytes solutions are established. The degree of dissociation of diallyammonium polymers is shown to depend both on the counterion nature and on the amine structure.     

Synthesis and characterization of D-2PA-Pd(II)@SBA-15 catalyst via “click chemistry”: highly active catalyst for Suzuki coupling reactions

Copper catalysed cycloaddition reaction between azide and terminal alkyne, called as “click reaction”, was found to be modular approach for the synthesis of facile, highly efficient and recoverable D-2PA-Pd(II)@SBA-15 catalyst. In efforts to synthesize the catalyst, the cycloaddition reaction between azido-functionalized mesoporous SBA-15 and N,N-dimethyl-2-propynylamine (D-2PA) has been carried out, followed by the complexation with PdCl₂. To analyze physiochemical properties of synthesized materials, various characterization techniques such as CHN elemental analysis, X-ray diffraction, solid state ¹³C and ²⁹Si NMR spectra, FT-IR, XPS, SEM, TEM and N₂ sorption analysis, TGA and DTA, UV–Vis spectroscopy have been carried out. The synthesized catalyst, D-2PA-Pd(II)@SBA-15, exhibited excellent catalytic activities with good product yield and high TON towards Suzuki coupling reaction of various aryl halides with phenylboronic acid. The effect of solvent, base and temperature on coupling reactions has also been described. The developed protocol offers recyclability of catalyst for multiple (four) times without any appreciable loss in stability and catalytic reactivity.     

Solvent optimization for efficient enzymatic monoacylglycerol production based on a glycerolysis reaction

This study was aimed at screening solvent systems of varying polarities to identify suitable solvents for efficient and practical enzymatic glycerolysis. Several pure solvents and solvent mixtures were screened in a batch reaction system consisting of glycerol, sunflower oil, and Novozym^® 435 lipase. Out of 13 solvents tested, tert-butanol and tert-pentanol were the only pure solvents suitable for a fast glycerolysis reaction with an acceptably high formation of MAG. In these systems, MAG contents of 68–82% were achieved within a few hours. Mixtures of tert-butanol/hexane, tert-pentanol/hexane, and tert-butanol/tert-pentanol in varying ratios also gave high MAG contents (58–78%). The tertiary alcohols tert-butanol and tert-pentanol, or mixtures of one of them with hexane, seemed to be the best choice among the solvents tested with respect to reaction efficiency, practical industrial applications, and steric hydroxyl group hindrance, which suppresses the ester formation with FA.     

Mixed Stability and Antimicrobial Properties of Gluconamide-Type Cationic Surfactants

The stability of anionic-cationic surfactant solutions and the antimicrobial properties of novel N,N-dimethyl-N-[3-(gluconamide/lactobionamide)]propyl-N-alkylammonium bromides (CnDGPB and CnDLPB), N-methyl-N-hydroxyethyl group-N-[3-(gluconamide)-propyl]-N-alkylammonium bromide (CnMHGPB) and star-shaped gluconamide-type cationic surfactants N-dodecyl-N,N-bis[(3-d-gluconylamido)propyl]-N-alkylammonium bromide (CnDBGB) were investigated. Mixed stability in combination with sodium n-alkylbenzenesulfonate (LAS) was determined via transmittance; stability is achieved when percent transmittance was greater than 90 %. Transmittance results suggest that these cationic surfactants can form stable solutions with anionic surfactants over a broad concentration range. The inhibition activity of C _n DBGB is the best among the three kinds of glucocationic surfactants. Antimicrobial activity of C₁₂ surfactants was the best, C₁₄ was the second and C₁₀ was the worst. Moreover, antibacterial activity of glucose-based cationic surfactants was greater than lactose-based cationic surfactants.     

Leakage currents and self-discharge of ionic liquid-based supercapacitors

Ionic liquid (IL)-based supercapacitors have been widely demonstrated to outperform electrochemical double-layer capacitors (EDLCs) working with conventional organic electrolytes in terms of specific energy and operating voltage. Here, the results of a study on the leakage currents (I _leak) and self-discharge energy loss factors (SDLF) of IL-based EDLCs at different cell voltages up to 3.2 V and at 30° and 60 °C are reported. Cells assembled with the N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl) imide (PYR₁₄TFSI) and N-methoxyethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide pure ILs and a mixture of PYR₁₄TFSI and propylene carbonate (PC) 1 to 1 molar were tested. The results are compared to those achieved with EDLCs featuring the conventional 1 M tetraethyl ammonium tetrafluoroborate (Et₄NBF₄)-PC electrolyte. The study demonstrates that ILs provide I _leak and SDLF that are lower than those obtained with the latter electrolyte, with PYR₁₄TFSI allowing the lowest values.     

Fluorene Derivatives with Multi-addressable Properties: Synthesis,Characterization, and Reactivity

A series of novel fluorene derivatives were synthesized from the target compound N-octadecyl-9-oxo-9H-fluorene-4-carboxamide (3), which led to new functionalized five- and six-membered heterocyclic derivatives via reaction with various reagents. The synthesized compounds were allowed to react with propylene oxide to afford unique surface-active properties. The chemical structures of the newly synthesized compounds were elucidated and confirmed by spectroscopic and analytical tools. The synthesized compounds have good surface activity and the biological degradation of these fluorene-based surfactants was greater than 96% after 7 days.     

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.     

Bio-/Environment-Friendly Cationic Gemini Surfactant as Novel Corrosion Inhibitor for Mild Steel in 1 M HCl Solution

Bio-/environment-friendly cationic gemini surfactant, ethane-1,2-diyl bis(N,N-dimethyl-N-hexadecylammoniumacetoxy)dichloride, referred to as 16-E2-16, was synthesized and characterized. Corrosion inhibition effects of 16-E2-16 on mild steel (MS) surface in 1 M HCl solution at 30, 40, 50 and 60 °C were evaluated using gravimetric analysis, potentiodynamic polarisation and electrochemical impedance spectroscopy measurements. The nature of the protective inhibitor film formed on the MS surface was analysed by SEM, EDAX and FT-IR, while TGA was used to assure the thermal behaviour and stability of the film at high temperature. The formation of [inhibitor-Fe²⁺] on the surface of MS was confirmed by UV–visible spectroscopy. The inhibition efficiency of the studied inhibitor increased with increasing concentration and solution temperature. The compound behaved as a mixed type inhibitor and acted by blocking the electrode surface by means of adsorption obeying the Langmuir adsorption isotherm. Surface active properties and corrosion inhibition effects of 16-E2-16 in the presence of inorganic (NaI) and organic (NaSal) salts were also investigated and are discussed. Density functional theory calculations have been carried out to correlate the efficiency of the compound with its intrinsic molecular parameters.     

Experimental review of microwave-assisted methods for synthesis of functional resins for sorption of rhenium(VII)

The microwave-assisted syntheses of anion exchange resins were carried out in the presence of selected organic solvents and amines, applying variable radiation density. The polymers were used for sorption of ReO₄^–, after which, the collected results were set together with the applied synthesis parameters. The greatest Re(VII) sorption capacity of 470 mg Re g^?1 was revealed by a resin obtained within 10 min in the presence of N,N-dimethylformamide and 2-methylimidazole at power of 160 W. The outcome of the present research constitutes a set of guides allowing to enhance the resource-efficiency of the process.     

Thermal stability,solubility, and fluorescence property of poly(arylene ether ketone)s bearing <Emphasis Type="Italic">N</Emphasis>-arylenebenzimidazole units

A series of novel random poly(arylene ether ketone)s containing N-arylenebenzimidazolyl groups with precise structures in high yields were synthesized from 2-(2′-hydroxyphenyl) benzimidazole and 4,4′-dihydroxybenzophenone with 4,4′-difluorobenzophenone via nucleophilic substitution polycondensation reaction using sulfolane as a solvent. The reaction was carried out at 210 °C in the presence of anhydrous potassium carbonate. The structures of the resulted polymers were characterized by means of FT-IR, ¹H NMR spectroscopy, and elemental analysis, and the results were largely consistent with the proposed structure. X-ray diffraction studies revealed that the incorporation of N-arylenebenzimidazolyl groups decreased the crystallinity of the resulted polymers. As the benzimidazole unit content in the copolymer increased, the solubility and thermal behavior of the prepared polymers improved. The novel poly(arylene ether ketone)s exhibited glass transition temperatures (T _gs) in the range 188–237°C, and there was a good linearity relationship between T _g values and the content of benzimidazolyl groups. The 5% decomposition temperatures were within the range of 512–539 °C in nitrogen and 496–540 °C in air indicating their good thermal stability. Tensile tests of the films showed that these polymers have desirable mechanical properties. Moreover, the resulting polymers showed good fluorescence properties.     

An organofunctionalized MgO∙SiO<Subscript>2</Subscript> hybrid support and its performance in the immobilization of lipase from <Emphasis Type="Italic">Candida rugosa</Emphasis>

Lipase from Candida rugosa was immobilized on MgO·SiO₂ hybrid grafted with amine, thiol, cyano, phenyl, epoxy and carbonyl groups. The products were analyzed using Fourier transform infrared spectroscopy, nuclear magnetic resonance, low-temperature N₂ sorption and elemental analysis. Additionally, the degree of coverage of the oxide material surface with different functional groups and the number of surface functional groups were estimated. The Bradford method was used to determine the quantity of immobilized enzyme. The largest quantity of enzyme (25-28 mg/g) was immobilized on the hybrid functionalized with amine and carbonyl groups. On the basis of hydrolysis reaction of p-nitrophenyl palmitate to p-nitrophenol, it was determined how the catalytic activity of the obtained biocatalysts is affected by pH, temperature, storage time, and repeated reaction cycles. The best results for catalytic activity were obtained for the lipase immobilized on MgO?SiO₂ hybrids with amine and carbonyl groups. The biocatalytic system demonstrated activity above 40% in the pH range 4–10 and in the temperature range 30–70 °C. Lipase immobilized on the MgO?SiO₂ systems with amine and epoxy groups retains, respectively, around 80% and 60% of its initial activity after 30 days of storage, and approximately 60–70% after 10 reaction cycles.     

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.     

Introduction of alkali soaking and microwave drying processes to improve agar quality of <Emphasis Type="Italic">Gracilaria verrucosa</Emphasis>

Gracilaria species produce agars with low quality due to their high sulfate concentrations. For this reason, the gel properties of many Gracilaria agars must be improved by appropriate processes. In this study, we developed an improved agar extraction process for Gracilaria verrucosa by alkali soaking extraction and microwave thawing and drying. Variables such as the seaweed to alkali volume ratio, extraction time, and alkali concentration were adjusted to optimize the yield and agar quality. The yield of the agar was maximized (34.5±0.6%) using 3% alkali concentration; the lowest yield (17.0±1.7%) was obtained with 1% alkali concentration. Agar gel strengths ranged from 462.0±7 to 627.3±11 g·cm^?2. We have developed a process for quickly producing an agar gel through thawing and drying using microwave radiation. This study shows the possibility of producing a high-value agar using alkali soaking extraction methods for nonedible G. verrucosa.     

Bioactivity kinetics of organic matter biodegradation and nitrification

Biodegradation of organic matter and nitrification of ammonia nitrogen was studied by measuring the electron transport system (ETS) activity in activated sludge. The feasibility of characterizing the bioactivity of activated sludge based on the ETS was discussed. Then, bioactivity kinetics for the biodegradation and nitrification of organic matter was analyzed using the Michaelis–Menten equation. The results indicated that the ETS activity of activated sludge reflects the progression of organic matter biodegradation and nitrification of ammonia nitrogen; moreover, ETS activity is sensitive to the loading of organic matter and ammonia nitrogen and also to changes in alkalinity during the reaction. Therefore, it is feasible to characterize the bioactivity of an activated sludge system with ETS activity. The Michaelis constant for organic matter biodegradation was K ^T s=368.9 mg/L; U ^T m=90.9 mgTF/(gTss·h); K ^I s=88.42 mg/L; and U ^I m=277.8 mgINTF/(gTss·h); for the nitrification of ammonia nitrogen, the Michaelis constant was K ^T s=16.89 mg/L; U ^T m=34.6 mgTF/(gTss·h); K ^I s=6.0 mg/L; and U ^I m=196.08 mgINTF/(gTss·h). Additional analyses of bioactivity kinetics confirmed that the organic matter oxidation rate of heterotrophic bacteria was higher than that of autotrophic nitrifying bacteria.