Short-chain Alkylamines Research Articles

Tough epoxy resin systems for cryogenic applications

This work presents the development of new epoxy systems that combine high fracture toughness at cryogenic temperatures (▪) with a slow curing reaction (long pot life) and a glass transition temperature between ▪ and ▪, ensuring good mechanical performance at room temperature. This was achieved by incorporating varying amounts and types of short-chain alkylamines into epoxy networks based on bisphenol A diglycidyl ether (DGEBA) crosslinked with metaphenylene diamine (MPD). This modification enhanced the cryogenic fracture toughness of the base system, DGEBA crosslinked with MPD, from 2 to ▪. It has been suggested that the significantly improved cryogenic fracture toughness in systems with flexible aliphatic chain extenders might result from nano- or micro-phase separation, but X-ray scattering and dynamic mechanical spectroscopy did not provide conclusive evidence for this hypothesis.The required slow curing reaction was achieved by using a sterically hindered alkylamine (2-heptylamine) as chain extender, which increased the pot life more than twofold, resulting in resin formulations that combine a high cryogenic fracture toughness, a low viscosity and a long processing window at room temperature.

Concentration of deposit patterns by nanoparticles modified with short amphiphiles

Depositing drops of a nanoparticle suspension onto a substrate is a simple way to model the processes that occur during printing of macroscopic structures from nanoparticles. We investigated the effect of adding short chain length amines on the deposit patterns formed by fused silica nanoparticles. Adding amphiphiles which adsorb at the particle surfaces is expected to modify their wettability and stability. Hence it should be possible to tune the particle interactions and control the patterns formed by the deposited particles. We probed the effects of amine adsorption on the silica particles by measuring the changes to the electrokinetic properties and wettability of the particles. Adding short chain amines to concentrated dispersions of silica nanoparticles induces a transition from a ring-shaped morphology to a more uniform, dot-shaped deposit during evaporative drying. We characterised the size and shape of deposits formed as a function of amphiphile chain length and concentration, and the particle concentration. The variation in the deposition pattern with the alkyl chain length can be accounted for by considering the effect of amine adsorption on the interactions between the particles and the interactions between the particles and the substrate. This is the first report showing how short chain alkylamines can be used to tune the deposition of silica nanoparticles.

Unprotonated Short-Chain Alkylamines Inhibit Staphylolytic Activity of Lysostaphin in a Wall Teichoic Acid-Dependent Manner.

Lysostaphin (Lst) is a potent bacteriolytic enzyme that kills Staphylococcus aureus, a common bacterial pathogen of humans and animals. With high activity against both planktonic cells and biofilms, Lst has the potential to be used in industrial products, such as commercial cleansers, for decontamination. However, Lst is inhibited in the presence of monoethanolamine (MEA), a chemical widely used in cleaning solutions and pharmaceuticals, and the underlying mechanism of inhibition remains unknown. In this study, we examined the cell binding and killing capabilities of Lst against S. aureus ATCC 6538 in buffered salt solution with MEA at different pH values (7.5 to 10.5) and discovered that only the unprotonated form of MEA inhibited Lst binding to the cell surface, leading to low Lst activity, despite retention of its secondary structure. This reduced enzyme activity could be largely recovered via a reduction in wall teichoic acid (WTA) biosynthesis through tunicamycin treatment, indicating that the suppression of Lst activity was dependent on the presence and amount of WTA. We propose that the decreased cell binding and killing capabilities of Lst are associated with the influence of uncharged MEA on the conformation of WTA. A similar effect was confirmed with other short-chain alkylamines. This study offers new insight into the impact of short-chain alkylamines on both Lst and WTA structure and function and provides guidance for the application of Lst in harsh environments.IMPORTANCE Lysostaphin (Lst) effectively and selectively kills Staphylococcus aureus, the bacterial culprit of many hospital- and community-acquired skin and respiratory infections and food poisoning. Lst has been investigated in animal models and clinical trials, industrial formulations, and environmental settings. Here, we studied the mechanistic basis of the inhibitory effect of alkylamines, such as monoethanolamine (MEA), a widely used chemical in commercial detergents, on Lst activity, for the potential incorporation of Lst in disinfectant solutions. We have found that protonated MEA has little influence on Lst activity, while unprotonated MEA prevents Lst from binding to S. aureus cells and hence dramatically decreases the enzyme's bacteriolytic efficacy. Following partial removal of the wall teichoic acid, an important component of the bacterial cell envelope, the inhibitory effect of unprotonated MEA on Lst is reduced. This phenomenon can be extended to other short-chain alkylamines. This mechanistic report of the impact of alkylamines on Lst functionality will help guide future applications of Lst in disinfection and decontamination of health-related commercial products.

Heterogeneous uptake of ammonia and dimethylamine into sulfuric and oxalic acid particles

Abstract. Heterogeneous uptake is one of the major mechanisms governing the amounts of short-chain alkylamines and ammonia (NH3) in atmospheric particles. Molar ratios of aminium to ammonium ions detected in ambient aerosols often exceed typical gas phase ratios. The present study investigated the simultaneous uptake of dimethylamine (DMA) and NH3 into sulfuric and oxalic acid particles at gaseous DMA ∕ NH3 molar ratios of 0.1 and 0.5 at 10, 50 and 70 % relative humidity (RH). Single-gas uptake and co-uptake were conducted under identical conditions and compared. Results show that the particulate dimethyl-aminium/ammonium molar ratios (DMAH ∕ NH4) changed substantially during the uptake process, which was severely influenced by the extent of neutralisation and the particle phase state. In general, DMA uptake and NH3 uptake into concentrated H2SO4 droplets were initially similarly efficient, yielding DMAH ∕ NH4 ratios that were similar to DMA ∕ NH3 ratios. As the co-uptake continued, the DMAH ∕ NH4 gradually dropped due to a preferential uptake of NH3 into partially neutralised acidic droplets. At 50 % RH, once the sulfate droplets were neutralised, the stronger base DMA displaced some of the ammonium absorbed earlier, leading to DMAH ∕ NH4 ratios up to four times higher than the corresponding gas phase ratios. However, at 10 % RH, crystallisation of partially neutralised sulfate particles prevented further DMA uptake, while NH3 uptake continued and displaced DMAH+, forming almost pure ammonium sulfate. Displacement of DMAH+ by NH3 has also been observed in neutralised, solid oxalate particles. The results can explain why DMAH ∕ NH4 ratios in ambient liquid aerosols can be larger than DMA ∕ NH3, despite an excess of NH3 in the gas phase. An uptake of DMA to aerosols consisting of crystalline ammonium salts, however, is unlikely, even at comparable DMA and NH3 gas phase concentrations.

Reactive Uptake of Dimethylamine by Ammonium Sulfate and Ammonium Sulfate-Sucrose Mixed Particles.

Short-chain alkyl amines can undergo gas-to-particle partitioning via reactive uptake by ammonium salts, whose phases have been thought to largely influence the extent of amine uptake. Previous studies mainly focused on particles of single ammonium salt at either dry or wet conditions without any addition of organic compounds. Here we report the uptake of dimethylamine (DMA) by ammonium sulfate (AS) and AS-sucrose mixed particles at different relative humidities (RHs) using an electrodynamic balance coupled with in situ Raman spectroscopy. DMA is selected as a representative of short-chain alkyl amines, and sucrose is used as a surrogate of viscous and hydrophilic organics. Effective DMA uptake was observed for most cases, except for the water-limiting scenario at <5% RH and the formation of an ultraviscous sucrose coating at 10% RH and below. DMA uptake coefficients (γ) were estimated using the particle mass measurements during DMA uptake. Addition of sucrose can increase γ by absorbing water or inhibiting AS crystallization and decrease γ by elevating the particle viscosity and forming a coating layer. DMA uptake can be facilitated for crystalline AS or retarded for aqueous AS with hydrophilic viscous organics (e.g., secondary organic material formed via the oxidation of biogenic volatile organic compounds) present in aerosol particles.

Effect of foamability index of short chain alkyl amines on flotation of quartz

Amines can be used for flotation of various minerals, especially quartz. The flotation efficiency of quartz depends on the amine type and dose. It was proved that the shorter alkyl amine, higher amine concentration has to be used to recover quartz at the same level. In flotation amines play a role of both collectors and frothers. The ability of a amine to collect particles can be expressed in the form of contact angle, while the foaming properties by different parameters including dynamic foamability index (DFI) and critical coalescence concentration (CCC). Determination of DFI and CCC requires advanced techniques and methods. Therefore, in this paper a rapid and facile method for determination of foaming properties of amines and also other surfactants was used. It was based on measuring the initial foam and froth heights in a conventional flotation machine at different concentrations of surfactants. The foam height-concentration curve was described by utilizing an empirical equation which was based on one-adjustable parameter called the foamability index (FI ). In this work the foamability index was determined for butylamine (ButNH2 ), hexylamine (HexNH2 ) and octylamine (OctNH2 ) as examples of short chain alkyl amines. The determined foamability indices were 92, 12 and 4 mg/dm3 for ButNH2 , HexNH2 and OctNH2 , respectively. It was shown that when the flotation results of quartz were presented in the form of recovery versus normalized amine concentration in relation to the foamability index (c/FI ), all the experimental data points converged to one curve. It indicates that amines act similarly but at different concentrations expressed as FI . The foamability index seems to be a useful parameter for characterizing any flotation frother.

A look inside particle stabilized foams—particle structure and dynamics

From a physico–chemical point of view, most food is soft matter. Usually, these systems are complex in the sense that they combine multiple ingredients with a wide range of structural length scales and dynamics on various time scales. Amongst these systems, foams belong to the well studied but less well understood systems. Particle stabilized foams are very common in food systems. As a model system, we produced aqueous foams from silica nanoparticle dispersions. The silica nanoparticles were hydrophobized by the in situ adsorption of short-chain alkyl amines of chain length C5 to C8 to render them surface active. We determined the role of the particles in stabilizing the produced foams. It is shown that the depletion of the bulk silica concentration during the foam formation can be quantified by precise density measurements. In the case of nanoparticle aggregation, more particles are trapped in the foam and will form a network in the foam channels. Diffusing wave spectroscopy was used to study the different time and length scales of the composite system. We find that it is possible to obtain the size of the particles within the foam by two different approaches. Additionally, the dynamics of the foam network is analyzed and it is confirmed that the formation of an aggregated particle network within the foam is responsible for a deceleration of the foam structure evolution.

Flotation and hydrophobicity of quartz in the presence of hexylamine

In this paper the influence of hexylamine, as an example of a short chain alkyl amine, on the flotation behaviour and interfacial properties of quartz was investigated. It was shown that hexylamine enhanced the flotation performance of quartz regardless of the type of flotation device. The foaming properties of hexylamine and its adsorption at the liquid/gas interface showed that hexylamine in the flotation process plays a role of a frother. It was also shown that hexylamine “uncovers” the natural hydrophobicity of quartz, which is sufficient to be attached to the liquid/gas interface.

Particle stabilized aqueous foams at different length scales: synergy between silica particles and alkylamines.

Nanoparticles can be efficient foaming agents. Yet, the detailed mechanisms of foam stabilization by these particles remain unclear. In most cases, the foamability and foam stability of a system have to be determined empirically. We used a multiscale approach to reveal how the microscopic properties of the nanoparticle dispersion are translated into their foaming behavior at the macroscopic scale. As a model system we used silica nanoparticles that were hydrophobized by the in situ adsorption of short-chain alkylamines of chain length C5 to C8. We used fluorescence spectroscopy and electrophoretic mobility measurements to characterize the bulk behavior of the nanoparticles with adsorbed amines. The interfacial behavior was probed by compressing particle monolayers while monitoring the surface tension. The macroscopic foamability and foam stability were evaluated. There are strong correlations between the system properties at all length scales. The most prominent effects are observed at a critical bulk concentration of amines at which the nanoparticles start to aggregate due to hydrophobic interactions. Our study shows how the foam properties are related to the features of the bulk dispersions and to the ordering of particles at the air/water interface. The present results help to understand the surfactant concentration dependent stages of foaming behavior of in situ hydrophobized nanoparticles.

Preparation of electrochromic Prussian blue nanoparticles dispersible into various solvents for realisation of printed electronics

An insoluble solid of historic Prussian blue (PB) was transformed into dispersible PB nanoparticles in water and various hydrophilic and hydrophobic organic solvents. Via hybrid surface modification using Na4[FeII(CN)6] and short-chain alkylamines, the insoluble PB was successfully dispersed in hydrophilic-and-hydrophobic boundary alcohols, such as n-butanol. The n-butanol-dispersible PB nanoparticles afforded homogeneous spin-coated thin films on various substrates. The chemisorbed shorter-chain alkylamines, n-propylamines, of the PB nanoparticles were thermally released at 100 °C from their surfaces to present stubborn electrochromic PB thin films adhering to the substrate via mutual coordination-bonding networks.

Low-Temperature Bonding Using Silver Nanoparticles Stabilized by Short-Chain Alkylamines

In this paper, we report on low temperature bonding using silver nanoparticles stabilized by short-chain alkylamines with different numbers carbon between 8 to 12. The bonding can be achieved by simultaneous heating and pressurization. The shear strength increased as the decomposition temperature of the stabilizer decreased. In the case of silver nanoparticles stabilized with n-octylamine (having the lowest decomposition temperature among the three stabilizers), the shear strength was 24 MPa for bonding at 400 °C. The difference in the shear strength is probably related to the amount of residual organic material in the sintering layer; the residual organic material would hinder the sintering of the silver nanoparticles, which was suggested by thermogravimetric analysis (TGA) results.

L-theanine intervention enhances human γδ T lymphocyte function

Human gammadeltaT lymphocytes are a subset of T cells and are a first line of defense against microbes and tumors. These gammadeltaT cells can be primed by nitrogen-containing bisphosphonates, and certain short-chain alkylamines. These primed gammadeltaT cells have an enhanced capacity to proliferate and to secrete cytokines upon ex vivo exposure to a wide variety of microbes and tumor cells. The largest dietary source of alkylamines is L-theanine, an amino acid unique to tea beverages that is catabolized to ethylamine. Supplementation of subjects with capsules containing L-theanine and catechins has recently been shown to decrease the incidence of cold and flu symptoms, while enhancing gammadeltaT cell function.

Incorporation of Short Chain Alkylamine in Template Micelle during MCM-41 Formation Process

In our previous report, ethylamine was confirmed to have an affirmative effect on the improvement of structural stability of MCM-41 mesostructure. It was also found that the addition of ethylamine causes structural changes. This report presents an in-depth study on the effect of alkylamine with a short alkyl chain by analyzing produced mesoporous structures. It is found that ethylamine dissolves into cetyltrimethylammoniumbromide (CTAB) micelles when it is added together with ethanol. Several different short chain alkylamines were also examined without adding ethanol. With an increase in the hydrophobic chain length, indications of amine participation as a cosurfactant are intensified. The amine species participating in the templating process is identified to be neutral. The amines conditioned in a pH range above pKa are found to strongly affect pore-to-pore distance and textural mesoporosity by dissolving themselves in micelles. Effect of short chain alkylamine is discussed with considerations of energy changes associated with micelle formation. [doi:10.2320/matertrans.M-MRA2007889]

Effect of Short-Chain Alkylamine on Micelle Structure in MCM-41 Synthesis Process

It was found that MCM-41 mesostructure can be strengthened by using ethylamine as a mineralizer in our previous study. The addition of ethylamine causes structural changes at the same time. In this report, important factors deciding micelle formation and possible changes in conformation of micelle when small amphiphilic materials co-exist are discussed. Incorporation of short-chain alkylamine in micelle is predicted by the energetical consideration if alkylamine is in neutral state and has an adequately hydrophobic chain part. Ethylamine which is supposed to be neutral in the pH range above pKa is found to incorporate in micelle when alcohol coexists together and increases hydrophobicity of ethylamine by forming complex with it. The same phenomenon takes place even without the addition of alcohol when alkylamine having a longer alkylchain such as propylamine and butylamine is used because of increased hydrophobicity.

A molecular model to explain paclitaxel and docetaxel sensitivity changes through adduct formation with primary amines in electrospray ionization mass spectrometry

The objective of this study was to adopt a molecular modeling approach to understand changes in signal intensity due to adduct formation with short-chain alkylamines for two anticancer agents, paclitaxel and docetaxel, during electrospray mass spectrometric analysis. We describe a simple and intuitive modeling procedure using a comparison of hydropathic interaction (HINT) scores to explain differences in responses of amine adducts formed with the two analytes. The responses of paclitaxel and docetaxel were generally enhanced considerably (up to approximately 500% in some instances) on adding the amines. However, for the docetaxel adduct formed with added decylamine in the mobile phase, the response dropped by 32%. A mechanistic understanding for this behavior is proposed, and binding scores calculated from corresponding molecular models were found to be consistent with the trend obtained from mass spectrometric data.

Synthesis of MFI metallosilicate zeolites using metallic amino complexes as mineralizing agents: an overview

The present overview, essentially dealing with the authors' recent laboratory work, consists of a critical evaluation of a series of new synthesis pathways leading to efficient formation and stabilization of several industrially important framework metal substituted MFI zeolites. More precisely, we critically discuss the potentialities and limitations of short-chain alkylamines as mobilizing–complexing agents for use as mineralizers for a variety of metallic ions in zeolite syntheses. A wide range of MFI zeolites containing various framework heteroatoms could be prepared in the presence of short-chain alkylamines. In particular, the mobilizing–complexing role of methylamine was investigated in more depth. The mineralizing power of methylamine can be very different from that of fluoride ions and basically depends on the nature of the metallic ion. The relative strength of the various amino complexes could be exploited to monitor and control the selective (simultaneous or successive) incorporation of various metallic species in the MFI framework. More than two heteroatoms were found to be incorporated per MFI unit cell in the case of Zn, Al, Ga, Fe, B, Ge and Ti. Cd 2+ and Cr 3+ ions only partly incorporate the MFI lattice (M n+ per unit cell<2). Copper, nickel, cobalt, manganese and molybdenum were found essentially admixed within the silicalite crystals, but they can be also partly anchored to the Al-MFI (negative) lattice as (strong) amino complex cationic species. At a similar complexing power, the (alkali-free) ‘amine route’ is preferred to the more conventional ‘fluoride route’, which involves a lower pH and less-supersaturated solutions, requiring very long crystallization times.

ChemInform Abstract: Use of Short Chain Alkylamines as Complexing—Mobilizing Agents: An Alternative to the “Fluoride Route” for the Synthesis of Zeolite Metallosilicate Catalysts

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Use of short chain alkylamines as complexing-mobilizing agents: An alternative to the “fluoride route” for the synthesis of zeolite metallosilicate catalysts

A wide series of zeolite metallosilicates was successfully synthesized using a series of short alkyl chain amines as new potential mineralizing agents. In the particular case of ZSM-5 containing various framework heteroatoms, the mobilizing-complexing role of methylamine, as compared to that of fluoride ions, can be very different and basically depends on the nature of the metallic ion. The relative strength of the various fluoro or amino complexes could be exploited to monitor and control the selective (simultaneous or successive) incorporation of various metallic species in the MFI framework. The incorporation, occurring in variable amounts, can be arbitrary considered as total (i.e. with more than 2 ionic species incorporated per MFI unit cell) for Zn2+, Al3+, Ga3+, Fe3+, B3+ and Ti4+. Cd2+ and Cr3+ are only partly incorporated (M/u.c.<2) while Cu2+, Co2+, Mn2+ and Mo5+ never incorporate the MFI lattice. Besides the fact that these ions do not readily achieve a tetrahedral coordination, the other possible reason could be that their polycondensation, if any possible, does not occur when these species are involved in too strong complexes with methylamine. In some cases (Cu2+, Fe2+, Ag+), methylamine behaves as a reducing agent in the synthesis medium and the corresponding metallic species are found admixed with silicalite. At similar complexing power, the (alkali-free) “amine route” is preferred to the now more conventional “fluoride route”, that involves lower pH and less supersaturated solutions, requiring very long crystallization times. These latter can also be drastically reduced by using fluoride-amine admixtures.

Micellar catalytic effect on the base dissociation of short-chain alkylamines studied by the ultrasonic adsorption method

Micellar catalytic effect on the base dissociation of short-chain alkylamines studied by the ultrasonic adsorption method

Methylamine Uptake by the Facultative Methylotroph Hyphomicrobium X

Hyphomicrobium X grows on methylamine as sole source of carbon, energy and nitrogen. The uptake of the compound occurred via a single inducible transport system irrespective of whether methylamine was used as a carbon and energy source or a nitrogen source only. The transport system had the following properties: temperature optimum 30 °C, pH optimum 7.0, K m approx. 70-100 nM, V max 12.5 nmol min-1 (mg dry weight)-1. Methylamine uptake was inhibited by azide, cyanide, N-ethylmaleimide and carbonyl cyanide-m-chlorophenyl-hydrazone. The uptake was not inhibited by ammonium ions, was slightly inhibited by amino acids and amides but was competitively inhibited by short-chain alkylamines (K i ethylamine 200 nM). Cells grown on formate, methanol or ethanol as C-source and ammonium sulphate as N-source did not possess the transport system but this could be induced by the presence of methylamine for 45-50 min. The addition of formate, methanol or ethanol to methylamine-grown cells did not affect the rate of methylamine uptake. Bacteria pre-grown on dimethylamine or trimethylamine transported methylamine into the cells at rates of 99% and 52%, respectively, when compared to rates with cells pre-grown on methylamine.