Diamine Concentration Research Articles

Elaboration and characterization of biodegradable poly(aspartic-co-glutamic acid) hydrogels as soil additives with different crosslinkers

This work introduces a promising biodegradable copolymer synthesized through the fusion of D,L-aspartic acid (ASP) and L-glutamic acid (GA) utilizing melt polymerization. Employing infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (1H NMR, 13C NMR), and X-ray diffraction (XRD), the copolymer’s structural characterization highlights its distinctive physicochemical attributes. The synthesis, conducted with a facile and controllable melt polymerization method, yielded a remarkable product yield of up to 81%. The optimization of water absorption properties involved a meticulous exploration of various diamine cross-linking agents—hexamethylene diamine (HMD), lysine (LYS), and a synthesized tartaric acid dihydrazide (TD) derivative. Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR), and scanning electron microscopy (SEM) were employed to confirm the copolymer’s structure, morphology, and cross-linking efficiency. The findings underscore exceptional water retention capabilities, with a peak swelling ratio of 11.874% achieved at a 10% concentration of hexamethylene diamine. Beyond advancing superabsorbent materials, this study contributes to mitigating environmental concerns associated with non-biodegradable alternatives.

Circularly Polarized Luminescent Eu4(LR)4 Cage for Enantiomeric Excess and Concentration Simultaneous Determination of Chiral Diamines.

Undoubtably, it is challenging to simultaneously determine the identity, enantiomeric excess (ee), and total concentration of an enantiomer by just one optical measurement. Herein, we design a chiral tetrahedron Eu4(LR)4 with circularly polarized luminescence (CPL), which presents highly selective/stereoselective, rapid, and "turn-on" CPL response to chiral diamines, rather than the monoamino compounds, such as monoamines or amino alcohols. By recording the left- and right-CPL intensities of the Eu3+ ion at 591 nm, the enantiomeric composition and concentration of chiral diamines can be simultaneously determined by monitoring the glum value and total emission intensity (IL + IR), respectively. Spectroscopy analyses demonstrate that the variations of glum depend on the inversion and maintenance of configuration around the Eu3+ ion (Δ ↔ Λ), while the "turn-on" response arises from the raising of the T1 state of the ligand. The molecule/electron structural variations are proposed from the synergetic supramolecular interactions of NH2 groups with pendant diols and trifluoroacetyl groups.

Emission of methylene diphenyl diisocyanate and methylene dianiline during use of cure-in-place methylene diphenyl diisocyanate-based consumer products.

The aim of this study was to provide realistic isocyanate and amine emission data when using different methylene diphenyl diisocyanate (MDI)-based polyurethane consumer products. Emission testing (air sampling) of diisocyanates and corresponding diamines was performed in a full-scale controlled-environment chamber during different work operations, such as gluing, mixing and foaming. The polyurethane products used were construction glue, one-component foam and two different two-component adhesives used in parquet flooring. Air sampling for isocyanates and amines was performed in the breathing zone of the worker and at different positions inside the controlled-environment chamber while the work operations were performed. Air sampling was also performed after the application, at different positions inside the chamber, to cover the post curing phase. Low air concentrations (0.1-0.7μg MDI/m3, 0.03-0.2μg isocyanate group (NCO)/m3) were found in the breathing zone and close to the work operation for some of the gluing applications. No methylene diphenyl diamine (MDA) concentrations above the limit of quantification were found for any of the applications in the breathing zone air. These results indicated that inhalation exposure to MDA or MDI would be expected to be minimal during application of do-it-yourself consumer products containing MDI.

Photocatalytic degradation of phenylene diamine using TiO2-rGO under UV radiation

In this study, phenylene diamine (an organic pollutant) was photo catalytically degraded by using TiO2-rGO nanoparticles in the UV radiation. Graphite powder was used to produce the rGO using modified hummers' method. Titanium isopropoxide was used to prepare TiO2 using hydrolysis. Hydrothermal method was used to produce TiO2-rGO nanoparticles. XRD and SEM were done to characterize the catalyst. The experiments under UV-light were conducted in the photo reactor to determine the percentage of degradation. The change in concentration vs time was observed with the change in absorbance value in the UV spectroscopy. The effect of catalyst concentration, phenylene diamine concentration and pH was also studied. Kinetics study was carried out and the degradation mechanism of phenylene diamine was discussed.

Antifungal activity of aminoalcohols and diamines against dermatophytes and yeast

Dermatomycoses are infections caused by fungi and yeasts and the drug treatment is considered expensive and extensive. Researchers are synthesizing new organic compounds in order to obtain more effective molecules that provide reduced adverse effects. Our research group has synthesized and evaluated the biological activities of aminoalcohol and diamine derivatives, which were considered active against human pathogenic fungi. Therefore, the objective of this study was to evaluate the in vitro antifungal activity of aminoalcohols and diamine derivatives against fungi and yeasts that cause dermatomycoses. The minimum inhibitory concentrations (MICs) and the minimum fungicidal concentration (MFC) of aminoalcohol (1–4) and diamine (5–13) derivatives was determined against Trichophyton mentagrophytes, T. rubrum, Epidermophyton floccosum, and Candida albicans according to protocols from the Clinical and Laboratory Standards Institute. All molecules exhibited fungicidal activity against the evaluated fungal strains, with the MIC and MFC ranging between 0.12 and 1000 μg/mL for filamentous fungi and 0.6 and 1250 μg/mL for yeasts. The best activity was attributed to diamines compared to aminoalcohols, with an emphasis on molecules 6 and 7. These results demonstrate the antifungal potential of the evaluated aminoalcohols and diamines against the four primary fungal species that cause dermatomycoses.

Flexible and Hydrophilic Copolyamide Thin-Film Composites on Hollow Fiber Membranes for Enhanced Nanofiltration Performance.

Flexible and hydrophilic copolyamide (Co-PA) thin-film composite (TFC) membranes were fabricated as a selective layer on the outer surface of the polyvinylidene fluoride hollow fiber membrane substrate. The fabrication process was carried out by the dip-coating method to create three TFC membranes. The first layer is tannic acid and the second layer is (3-aminopropyl)triethoxysilane, which is followed by Co-PA as a final selective layer. The Co-PA TFC membrane was prepared through interfacial polymerization via the combination of various short-chain aliphatic diamines and conventional aromatic diamines with trimesoyl chloride. The influence of coating layers and total diamine concentration on the Co-PA TFC membrane was investigated in terms of the membrane's physicochemical and mechanical properties, morphology, surface thickness and roughness, water contact angle, surface charge, and nanofiltration (NF) performance. The obtained Co-PA TFC membrane system was operated under low pressure (2 bar) with pure water flux in the range of 23.8-83.9 L m-2 h-1 and exhibited better hydrophilicity, flexibility, molecular weight cutoff, and NF performance compared to the conventional PA TFC membrane. The superior properties of Co-PA are due to the increased chain mobilities provided by short-chain aliphatic diamines in its structure. The best Co-PA TFC membranes, which were synthesized using diamines containing four carbon atoms, achieved a significant improvement in NF membrane performance and selectivity (pure water flux = 56.9 L m-2 h-1 and salt and dye rejection in the range of 46.2-99.2%). This Co-PA TFC membrane is a promising membrane for its high flexibility, hydrophilicity, and selectivity of the NF membrane.

Synthesis of Polyketone Anion Ion Exchange Fibers by Paal-Knorr Reaction and Its Physico-Chemical Properties

In this study, polyketone anion exchange fibers were synthesized by the amination of polyketone via a Paal-Knorr reaction and a quaternization reaction. The amination reaction proceeded at different reaction times and amine N,N-dimethylethylene diamine (DME) concentrations. The ion exchange capacity (IEC) and water uptake (W.U.) increased with increasing amination reaction time and DME concentration, and the maximum IEC and W.U. were 1.03 meq/g and 19.2%, respectively. The tensile strength decreased significantly with increasing amination time and amine concentration. TGA showed that the thermal decomposition temperature of the fibers was 220 °C. The HCl gas adsorption properties of the aminated polyketone ion exchange fibers were evaluated, and the HCl gas removal efficiency remained at 100% in 40 min at 300 ppm.

Effect of Diamine Addition on Structural Features and Physical Properties of Polyamide 6 Synthesized by Anionic Ring-Opening Polymerization of ε-Caprolactam.

Synthesis of ε-caprolactam in a twin screw extruder by anionic ring-opening polymerization was successfully carried out to prepare a novel nylon 6 (polyamide 6 (PA6)) containing a small amount of diamine moiety. The produced PA6 shows a remarkable improvement of the physical properties (mechanical properties as well as rheological properties). Added diamine molecules led to some structural changes in the synthesized PA6. The molar ratio of the additive (diamine) to the initiator appeared to be optimum at ca. 0.1. Although the molar mass of the PA6 has not changed significantly, less than twice the PA6 molar mass, the physical properties of the polymers produced have been markedly improved. The zero shear rate viscosity of the PA6 at the optimum diamine concentration appeared to be increased by almost 30 times that of the pure PA6. We have attributed this remarkable increase in viscosity to structural changes (branching formation during synthesis) and increased molar mass. The storage modulus at a low shear rate increased more than 100 times that of the pure PA6, but the loss modulus increased only 10-fold. This indicates that the elastic properties dominated due to the enhanced chain entanglements. In addition, the mechanical properties were significantly improved at the optimal amount of diamine reagent concentration. The elongation at break for the sample with optimum diamine addition was increased to twice that of neat PA6, whereby the tensile toughness was also doubled. Produced PA6 has a merit of processibility in the extrusion process such as a blow molding process in which stability against sagging under gravity is required and other processes in which elongational properties dominate.

Simultaneous Removal of SO2 and NO by Using Piperazine-urea-triethylene Diamine Ternary System

Performance of simultaneous removal of SO2 and NO from the simulated thermal power plants gas using piperazine-urea-triethylene diamine ternary system absorbent was investigated in this paper. Furthermore, the influences of the concentration of triethylene diamine, pH value, the absorption temperature and the total inlet flow rate of the simulated gas on simultaneous absorption behavior were discussed by means of the removal efficiency of SO2 and NO. A better simultaneous desulfurization and denitration behavior could be obtained under the absorption condition of triethylene diamine concentration of 0.3 mol/L, pH value of 6, inlet simulated gas flow rate of 500 ml/min, and the absorption temperature of 40 °C. Under the above absorption condition, the simultaneous NO removal efficiency of 70.28% and SO2 removal efficiency of 99.30% could be obtained.

Solubility of CO2 in aqueous solutions of DAMP+MDEA, DAMP+MEA, DAH+MDEA and DAH+MEA

The main goal of this research is to investigate absorption rate and capacity of carbon dioxide in aqueous mixtures of DAMP(1,5-Diamino-2-methylpentane)+MDEA(Methyl-diethanolamine), DAMP+MEA(Monoethanolamine), DAH(1,6-Diaminohexane)+MDEA and DAH+MEA in an isothermal stirred batch reactor. The experiments are designed in temperature ranging from 30 to 50 °C, at low pressure and various molar ratios. The results show that although there is an interaction between diamine and conventional amines at low diamine concentration, after a minimum absorption point, increasing DAMP and DAH concentration in conventional amines increases absorption capacity of solutions in all temperatures. Then, a rate equation is developed to predict absorption rate of aqueous solution of DAMP based on Zwitterion mechanism. The kinetic constant and order of reaction are determined considering the absolute difference between measured and predicted rate as the objective function. The results show that the reaction is first order with respect to amine concentration and third order in overall.

Dual inhibition effects of diamines on the formation of methane gas hydrate and their significance for natural gas production and transportation

Dual (thermodynamic and kinetic) inhibition effects of piperazine (PZ) and hydrazine (HZ), two representative diamines, on the formation of CH4 hydrate were investigated, primarily focusing on thermodynamic, spectroscopic, and computational analyses for their potential application in natural gas production and transportation. The phase behavior demonstrated that the addition of PZ and HZ shifts the CH4 hydrate equilibrium lines to higher pressure or lower temperature regions depending on diamine concentrations. The 13C NMR and Raman spectra of the CH4+diamine hydrates revealed that PZ and HZ are not enclathrated in the cages of CH4 hydrate and do not affect the hydrate structure. The time-dependent growth patterns and the induction time of CH4 hydrate in the presence of diamines were observed via in-situ Raman spectroscopy. HZ showed a more significant thermodynamic inhibition effect, slower hydrate growth, and longer induction time than PZ did. Interaction energy calculation using density functional theory (DFT) indicated that diamine molecules could disrupt the hydrogen bonding networks of hydrate cages, leading to destabilization of gas hydrate and retardation of hydrate nucleation and growth. Experimental and computational results demonstrated that both PZ and HZ can function as both kinetic and thermodynamic hydrate inhibitors for CH4 hydrate.

Dissociation of cephamycin C and clavulanic acid biosynthesis by 1,3-diaminopropane in Streptomyces clavuligerus.

Streptomyces clavuligerus produces simultaneously cephamycin C (CephC) and clavulanic acid (CA). Adding 1,3-diaminopropane to culture medium stimulates production of beta-lactam antibiotics. However, there are no studies on the influence of this diamine on coordinated production of CephC and CA. This study indicates that 1,3-diaminopropane can dissociate CephC and CA productions. Results indicated that low diamine concentrations (below 1.25 g l(-1)) in culture medium increased CA production by 200%, but not that of CephC. Conversely, CephC production increased by 300% when 10 g l(-1) 1,3-diaminopropane was added to culture medium. Addition of just L-lysine (18.3 g l(-1)) to culture medium increased both biocompounds. On the other hand, while L-lysine plus 7.5 g l(-1) 1,3-diaminopropane increased volumetric production of CephC by 1100%, its impact on CA production was insignificant. The combined results suggest that extracellular concentration of 1,3-diaminopropane may trigger the dissociation of CephC and CA biosynthesis in S. clavuligerus.

Enhanced thermal properties of phthalonitrile networks by cooperating phenyl-s-triazine moieties in backbones

The development of phthalonitrile resins is of particular interest for aerospace applications because of their excellent heat resistance. Here, heteroaromatic phenyl-s-triazine moieties have been introduced into the architecture of the phthalonitrile resin as thermally stable segments via a two-step, one-pot reaction. Bis(4-[4-aminophenoxy]phenyl)sulfone was selected to promote the curing reaction, and the gelation time could be readily controlled by the diamine concentration and the curing temperature as evidenced by rheometric measurements. The curing procedure was optimized to give high cross-linking density networks. The resulting networks exhibit high glass transition temperatures at around 400 °C, outstanding thermo-oxidative stability with weight retention of 95% ranging from 539 °C to 552 °C, suggesting an improvement of the thermal properties imposed by phenyl-s-triazine units. Additionally, the CF laminate of the resin possesses high flexural strength of 1722 MPa and interlaminar shear strength of 71 MPa at ambient temperature, and these values retain 255 MPa and 36 MPa at 450 °C, respectively.

Stirring-induced growth of hierarchical Cu structures in the presence of diamine

We propose a novel strategy for the synthesis of materials with a hierarchical structure. This strategy is based on in situ combination of two processes, namely, capping agent-mediated oriented growth and stirring-induced aggregation, and the growth of Cu crystals in the presence of linear alkyl diamines of short carbon chain length under vigorous stirring is shown to demonstrate its feasibility. Our experimental results have shown that the oriented growth of Cu nanowires can be significantly disturbed by vigorous stirring, resulting in large-scale growth of hierarchical dendritic Cu crystals. The morphology of grown dendritic Cu crystals has been found to vary with the stirring rate, type of diamine, and diamine concentration, which makes it possible to prepare hierarchical Cu structures of various morphologies. The growth mechanism of these hierarchical Cu structures is proposed based on the experimental observations. The present unique strategy offers a fresh way to fabricate materials with a hierarchical structure.

Chiral Recognition by Fluorescence: One Measurement for Two Parameters

This outlook describes two strategies to simultaneously determine the enantiomeric composition and concentration of a chiral substrate by a single fluorescent measurement. One strategy utilizes a pseudoenantiomeric sensor pair that is composed of a 1,1′-bi-2-naphthol-based amino alcohol and a partially hydrogenated 1,1′-bi-2-naphthol-based amino alcohol. These two molecules have the opposite chiral configuration with fluorescent enhancement at two different emitting wavelengths when treated with the enantiomers of mandelic acid. Using the sum and difference of the fluorescent intensity at the two wavelengths allows simultaneous determination of both concentration and enantiomeric composition of the chiral acid. The other strategy employs a 1,1′-bi-2-naphthol-based trifluoromethyl ketone that exhibits fluorescent enhancement at two emission wavelengths upon interaction with a chiral diamine. One emission responds mostly to the concentration of the chiral diamine and the ratio of the two emissions depends on the chiral configuration of the enantiomer but independent of the concentration, allowing both the concentration and enantiomeric composition of the chiral diamine to be simultaneously determined. These strategies would significantly simplify the practical application of the enantioselective fluorescent sensors in high-throughput chiral assay.

Role of amine oxidase expression to maintain putrescine homeostasis in Rhodococcus opacus

While applications of amine oxidases are increasing, few have been characterised and our understanding of their biological role and strategies for bacteria exploitation are limited. By altering the nitrogen source (NH4Cl, putrescine and cadaverine (diamines) and butylamine (monoamine)) and concentration, we have identified a constitutive flavin dependent oxidase (EC 1.4.3.10) within Rhodococcus opacus. The activity of this oxidase can be increased by over two orders of magnitude in the presence of aliphatic diamines. In addition, the expression of a copper dependent diamine oxidase (EC 1.4.3.22) was observed at diamine concentrations>1mM or when cells were grown with butylamine, which acts to inhibit the flavin oxidase. A Michaelis–Menten kinetic treatment of the flavin oxidase delivered a Michaelis constant (KM)=190μM and maximum rate (kcat)=21.8s−1 for the oxidative deamination of putrescine with a lower KM (=60μM) and comparable kcat (=18.2s−1) for the copper oxidase. MALDI–TOF and genomic analyses have indicated a metabolic clustering of functionally related genes. From a consideration of amine oxidase specificity and sequence homology, we propose a putrescine degradation pathway within Rhodococcus that utilises oxidases in tandem with subsequent dehydrogenase and transaminase enzymes. The implications of PUT homeostasis through the action of the two oxidases are discussed with respect to stressors, evolution and application in microbe-assisted phytoremediation or bio-augmentation.

Sensing of the concentration and enantiomeric excess of chiral compounds with tropos ligand derived metal complexes

Palladium(II) complexes carrying chromophoric tropos ligands show a characteristic UV change and strong Cotton effects upon coordination of amino alcohols or diamines. The distinct (chir)optical responses can be used for instantaneous in situ determination of the concentration and ee of diamines and amino alcohols at low concentrations.

Amino acid profile of plasma and cerebrospinal fluid in preeclampsia

ObjectivesTo determine patterns in amino acids (arginine, GABA, glutamate and glutamine) and the diamine (agmatine) in plasma and cerebrospinal fluid (CSF) of mild and severe preeclampsia compared to control patients, using capillary zone electrophoresis to generate methods for refining diagnosis and prognosis and shed light on the pathophysiological mechanisms of preeclampsia. Study designThis is an observational case-control study in pregnant women that attended the emergency ward of the University Hospital, Mérida, Venezuela, during the period April, 2009–April 2010. Main outcome measuresMolar concentration of amino acids and diamine in plasma and CSF in control, mild and severe preeclampsia patients. ResultsAn increase in glutamate plasma levels was observed in mild preeclampsia and even higher in severe patients, while a biphasic response occurred in the CSF samples with a significant increment in mild preeclampsia patients and a decrease in severe preeclampsia patients. GABA significantly decreased both in plasma and CSF in mild preeclampsia with a tendency to return to normal levels in severe preeclampsia patients. Arginine CSF and plasma levels decreased in mild preeclampsia patients and even more in severe preeclampsia while agmatine significantly increased in plasma levels with no changes in CSF. ConclusionsThe results are discussed in terms of molecules that could be used as biomarkers of the severity of the disease and the possible involvement of these substances in the pathophysiology of preeclampsia.

Easy to use spectrophotometric method for determination of aromatic diamines in biodiesel samples

Biodiesel is the main partial substitute for petrodiesel. Some biodiesels have low oxidative stability. To solve or minimize this problem, some compounds have been added to biodiesel as antioxidants. One of the most efficient classes of compounds used for this is aromatic diamines because of their high antioxidant capacity at low concentration. Aromatic diamines can be used as artificial markers. It is sometimes necessary to determine the concentration of antioxidants in biodiesel after long storage times or to control quality. An easy to use spectrophotometric methodology was employed in this work to determine the concentration of aromatic diamines (0 to 500ppm). Five calibration curves were constructed using 3 absorption frequencies from the infrared spectra of the samples. The standard deviation, correlation coefficient, linearity range, limit of detection and limit of quantification were determined. The better results from the easy to use method (814cm−1) show a linear range of 0–100ppm with a strong correlation (R2=0.9966) and a limit of quantification of 21.6ppm.

In-depth study on aminolysis of poly(ɛ-caprolactone): Back to the fundamentals

The aminolysis can effectively introduce primary amine (−NH2) groups onto polyester materials, enabling a variety of subsequent surface biofunctionalization reactions. However, less attention has been paid to the basic knowledge of aminolysis reaction in terms of reaction kinetics and its influences on materials properties. In this study, taking the widely used poly(ɛ-caprolactone) (PCL) as a typical example, the influences of diamines and solvent property on the surface −NH2 density are firstly assessed by using X-ray photoelectron spectroscopy (XPS) and colorimetric analysis. Results show that smaller diamine molecules and nonpolar alcohols could accelerate the reaction. The reaction kinetics with 1,6-hexanediamine is further investigated as a function of temperature, reaction time, and diamine concentration. During the initial stage, the reaction shows a 1st order kinetics with the diamine concentration and has an activation energy of 54.5 kJ/mol. Ionization state of the −NH2 groups on the PCL surface is determined, revealing that the pKa of −NH3+ (<5) is much lower than that of the corresponding diamine molecules in solution. After aminolysis, surface hydrophilicity of PCL membrane is significantly enhanced, while surface elastic modulus and average molecular weight are decreased to some extent, and others such as weight, surface morphology and bulk mechanical strength are not apparently changed. The introduced −NH2 groups are found to be largely lost at 37 °C, but can be mostly maintained at low temperature.