Alkyltrimethylammonium Ions Research Articles

Adsorption of gaseous aromatic compounds by linear quaternary ammonium-modified γ-zirconium phosphate

In this work, the intercalation of alkyl trimethylammonium ion (CnN+) and dialkyl dimethylammonium ion (2CnN+) were attempted for α‑zirconium phosphate (α-ZrP) and γ-ZrP. And then a pure intercalation compounds were obtained only for γ-ZrP. It was expected that the intercalation of linear quaternary ammonium ion would produce not only a hydrophobic environment in the interlayer space but also form an appropriate void for the adsorption of hydrophobic air pollutants. The basal spacing of 2CnN+-intercalated γ-ZrP was greater than that of CnN+-intercalated γ-ZrP because CnN+ was arranged in a mono-molecular structure in the interlayer space contrary to the bi-molecular structure of 2CnN+. Furthermore, the alkyl chain in the interlayer space of γ-ZrP was in a gauche form for CnN+, for a smaller carbon number (n), and changed to a trans structure for a larger n. γ-ZrP with a modified interlayer space could adsorb gaseous aromatic hydrocarbons contrary to the nonmodified γ-ZrP. Maximum adsorption was attained for C18N+-intercalated γ-ZrP with a mono-molecular structure and trans structure alkyl chain, although the basal spacing and uptake of alkyl ammonium reached a maximum for 2C18N+-intercalated γ-ZrP. Hence, not only the basal spacing and carbon number but also the void space in the interlayer region affected adsorption. It was interesting to note that the conformation of the long alkyl chain was reversibly changed through adsorption and desorption.

Effect of Alkyltrimethylammonium Ions on Corrosion and Electrochemical Behavior of Pb-Ca-Sn Alloy

Effect of Alkyltrimethylammonium Ions on Corrosion and Electrochemical Behavior of Pb-Ca-Sn Alloy

Molecular Understanding on the Underwater Oleophobicity of Self-Assembled Monolayers: Zwitterionic versus Nonionic.

Molecular dynamics simulations are conducted to investigate the underwater oleophobicity of self-assembled monolayers (SAMs) with different head groups. Simulation results show that the order of underwater oleophobicity of SAMs is methyl < amide < oligo(ethylene glycol) (OEG) < ethanolamine (ETA) < hydroxyl < mixed-charged zwitterionic. The underwater-oil contact angles (OCAs) are <133° for all nonionic hydrophilic SAMs, while the mixed-charged zwitterionic SAMs are underwater superoleophobic (OCA can reach 180°). It appears that surfaces with stronger underwater oleophobicity have better antifouling performance. Further study on the effect of different alkyl ammonium ions on mixed-charged SAMs reveals that the underwater OCAs are >143.6° for all SAMs; mixed-charged SAMs containing primary alkyl ammonium ion are likely to possess the best underwater oleophobicity for its strong hydration capacity. It seems that alkyl sulfonate anion (SO3-) is more hydrophilic than alkyl trimethylammonium ion (NC3+) for the hydrophobic methyl groups on nitrogen atoms and that the hydration of SO3- in mixed-charged SAMs can be seriously blocked by NC3+. The monomer of SO3- should be slightly longer than that of NC3+ to obtain better underwater oleophobicity in NC3+-/SO3--SAMs. In addition, the underwater oleophobicity of SAMs might become worse at low grafting densities. This work systematically proves that a zwitterionic surface is more underwater oleophobic than a nonionic surface. These results will help for the design and development of superoleophobic surfaces.

Matrix-enhanced adsorption removal of trace BPA by controlling the interlayer hydrophobic environment of montmorillonite

There is an increased concern recently toward Bisphenol A (BPA), a typical phenolic type estrogenic endocrine disruptor compound, because of its potential impact toward both human beings as well as wildlife at a trace concentration level. In this research, the surfactant-modified montmorillonite materials were used aiming at the complete removal of trace BPA in water environment. Through a detailed examination on the intercalation properties of alkyltrimethylammonium ions, the interlayer hydrophobic environment properties of the clay minerals, and their relationship with the BPA equilibrium adsorption, it is concluded that BPA at a trace concentration level can be completely removed through increasing the chain length of the surfactant intercalates. Sufficient interlayer hydrophobicity, realized by near or excess cation exchange capacity intercalation of longer chain surfactants, is found significant to the enhancement of selective adsorption of BPA while coexisting with matrix organic substances, which is substantially instructive to the removal of other kinds of non-ionic emerged organic contaminants.

Rigidochromic Phosphorescence of [Ir(2‐phenylpyridine)2(2,2′‐bipyridine)]+ in C16TMA+: Layered Silicate and Its Förster Resonance Energy Transfer

AbstractLayered silicate–[Ir(2‐phenylpyridine)2(2,2′‐bipyridine)]+ {[Ir(ppy)2(bpy)]+} composites were synthesized by the ion exchange between the intercalated alkyltrimethylammonium ions and [Ir(ppy)2(bpy)]+ ions. The loading amounts of the Ir complexes were increased by an increase in the reaction temperature. The photophysical properties of the samples were characterized by the luminescence spectra and luminescence lifetimes. The photophysical properties of Ir complexes were affected by the loading amount in the interlayer space, which resulted in higher‐energy phosphorescence emission. The higher‐energy state in the low‐loading samples was applied to Förster resonance energy transfer to the exterior acceptor molecules.

Interaction of the model alkyltrimethylammonium ions with alkali halide salts: an explicit water molecular dynamics study

We present an explicit water molecular dynamics simulation of dilute solutions of model alkyltrimethylammonium surfactant ions (number of methylene groups in the tail is 3, 5, 8, 10, and 12) in mixture with NaF, NaCl, NaBr, and NaI salts, respectively. The SPC/E model is used to describe water molecules. Results of the simulation at 298 K are presented in the form of radial distribution functions between nitrogen and carbon atoms of CH$_2$ groups on the alkyltrimethylammonium ion, and the counterion species in the solution. The running coordination numbers between carbon atoms of surfactants and counterions are also calculated. We show that I$^-$ counterion exhibits the highest, and F$^-$ the lowest affinity to "bind" to the model surfactants. The results are discussed in view of the available experimental and simulation data for this and similar solutions.

Attachment of the Sulfonic Acid Group in the Interlayer Space of a Layered Alkali Silicate, Octosilicate

The surface modification of a layered alkali silicate, octosilicate (Na(2)Si(8)O(17)·nH2O), with a sulfonic acid group was conducted. The sulfonic acid group was attached to the silicate layer by the reaction of octosilicate with phenethyl(dichloro)methylsilane and the subsequent sulfonation of the attached phenethyl groups with chlorosulfonic acid. The modified octosilicate is a solid acid as indicated by the intercalation of dodecylamine. A systematic expansion of the interlayer space was observed by the ion exchange with a series of alkyltrimethylammonium ions to show the variation of the layer charge density.

Aggregation of Alkyltrimethylammonium Ions at the Cleaved Muscovite Mica–Water Interface: A Monte Carlo Study

The precise molecular structure of organically modified mineral surfaces is still not well understood. To establish a relation between experimental observations and underlying molecular structure, we performed Monte Carlo simulations of the aggregation behavior of alkyltrimethylammonium surfactants (C(n)TMA(+)) at the interface between C(n)TMACl solution and cleaved K(+)-muscovite. The structures were examined with regard to the influence of varying alkyl chain length n (n = 8, 12, 16) and surface coverage of C(n)TMA(+) ions. The simulation results indicate that the water film structure at the muscovite surface is considerably influenced by the adsorption of C(n)TMA(+). A fraction of the C(n)TMA(+) ions forms inner-sphere and outer-sphere adsorption complexes with nitrogen-surface distances of 3.3-3.8 and 5.5-8.4 Å, respectively. The simulated monolayer aggregates exhibit thicknesses of 31-35, 22-27, and ∼18 Å for C(16)TMA(+), C(12)TMA(+), and C(8)TMA(+), respectively. C(16)TMA(+) and C(12)TMA(+) ions form bilayer aggregates, which show a strong interdigitation of the two opposing layers composing them. The aggregate thicknesses equal 35-39 and 30-35 Å, respectively, and are in agreement with available experimental data. In contrast, the short-chained C(8)TMA(+) ions do not form bilayer aggregates. In agreement with previous experimental studies, the alkyl chains of the aggregated ions show high conformational order markedly decreasing with decreasing chain length. We suggest that the simulated structures represent C(n)TMA(+) aggregates, which are formed on muscovite during the experimentally observed initial equilibration phase characterized by the presence of inorganic ions within the aggregates.

Fluorescence spectroscopy of fulvic acids’ interaction with surfactants

Fluorescence spectra of two fulvic acid (FA) samples, FA0 from underground water and FA1 from forest soil, were recorded in various surfactant solutions. Alkyltrimethylammonium ions with different alkyl chain lengths induced a decrease in the fluorescence intensity for both FAs at concentrations below the critical micelle concentration (cmc) and an enhancement above the cmc. The intensity minimum thus obtained at the cmc was deeper for surfactants with longer alkyl chains. This effect was attributable to the formation of insoluble FA–surfactant complexes below the cmc and to the solubilization of the complex into micelles above the cmc. Dodecylpyridinium chloride caused a monotonic decrease in the FA fluorescence even far above the cmc. This was attributable to the quenching of FA fluorescence by the positioning of the pyridinium head group near the FA fluorophore. Anionic and nonionic surfactants showed little to no effect on the FA fluorescence.

Binding Modes of a trans-Vinylbipyridinium Surfactant Bearing a Hexadecyl Chain to Cucurbit[n]uril (n = 6-8) in Aqueous Solution

Alkyl chains of naturally occurring fatty acids usually adopt the strain-free extended conformation in solution or gas phase. However, the conformations of alkyl chains are highly environment-dependent. Sometimes they adopt unusual, seemingly high-energy conformations. For example, alkyl chains confined in synthetic hosts adopt helical conformations. Another example is U-shaped conformations. Fatty acid binding proteins (FABPs) offer special environments for fatty acids such as palmitic acid and oleic acid to adopt a “U-shaped” conformation. The back-folding phenomenon of aliphatic chains found in Nature was scarcely observed in synthetic systems until recently. An alkyl chain bound to the cavity of γ-cyclodextrin (γ-CD) was suggested to adopt a U-shaped conformation based on fluorescence life-time measurements, which has never been confirmed, however. Recently, we reported an unequivocal example of the back-folding of aliphatic chains bound to a synthetic host. The alkyl chains of alkyltrimethylammonium ions bound to a hydrophobic cavity of cucurbit[8]uril (CB[8]), a member of host family cucurbit[n]uril (CB[n], n = 5-10), adopt a U-shaped conformation, which has been unequivocally characterized by various methods. However, the same alkyl chains of alkyltrimethylammonium ions were found to have an extended conformation when bound to CB[6] or CB[7]. Extending this work, we investigated the host-guest complex formation of CB[n] with other types of amphiphilic molecules containing a long alkyl chain. Herein, we report different binding modes of an amphiphilic molecule comprising a vinylbipyridinium unit as a polar head and a hexadecyl chain as a hydrophobic tail to CB[n] (n = 6, 7, and 8) in aqueous solution, and discuss the different conformations adopted by the alkyl chain.

U‐Shaped Conformation of Alkyl Chains Bound to a Synthetic Host

Taking it in turn: Despite the high internal strain, the long aliphatic chains of alkyltrimethylammonium ions buried deeply inside the cucurbit[8]uril (CB[8]) cavity adopt a U-shaped conformation (see X-ray structure), which is stabilized by electrostatic and van der Waals interactions with the carbonyl-laced portal and hydrophobic cavity of CB[8]. This conformation is similar to that of fatty acids bound to fatty acid binding proteins.

Capillary electrochromatography‐mass spectrometry of cationic surfactants

The CEC-MS of alkyltrimethylammonium (ATMA+) ions with chain lengths ranging from C1-C18 is optimized using an internally tapered column packed with mixed mode reversed phase/strong cation exchange stationary phase. A systematic study of the CEC separation parameters is conducted followed by evaluation of the ESI-MS sheath liquid and spray chamber settings. First, the optimization of CEC separation parameters are performed including the ACN concentration, triethylamine (TEA) content, buffer pH and ammonium acetate concentration. Using 90% v/v ACN with 0.04% v/v TEA as mobile phase, the separation of longer chain C6-C18-TMA+ surfactants could be achieved in 15 min. Lowering the ACN concentration to 70% v/v provided resolution of shorter chain C1, C2-TMA+ from C6-TMA+ although the total analysis time increased to 40 min. Furthermore, variation of both the ACN and TEA content as well as ionic strength has found to significantly influence the retention of longer chain surfactants as compared to shorter chains. The optimum CEC conditions are 70% v/v ACN, 0.04% v/v TEA, pH 3.0 and 15 mM ammonium acetate. Next, the optimization of the ESI-MS sheath liquid composition is conducted comparing methanol to isopropanol followed by the use of experimental design for analysis of spray chamber parameters. Overall, the developed CEC-ESI-MS method allows quantitative and sensitive monitoring of ATMA+ from < or =10 microg/mL down to 10 ng/mL. Utilizing the optimized CEC-ESI-MS protocol, the challenging analysis of commercial sample Arquad S-50 ATMA+ containing cis-trans unsaturated and saturated soyabean fatty acid derivatives is demonstrated.

Preparation and properties of intercalation compounds of graphite oxide

Preparation and characterization of various intercalation compounds of graphite oxide were summarized. The hydroxyl groups with acidic nature in graphite oxide were responsible for the intercalation of various reagents including alkyltrimethylammonium ions, alkylamines and silylating reagents. The size of the empty space in the interlayer spacing of the resulting intercalation compounds varied in a wide range by changing the kind or amounts of intercalated species. They possessed hydrophobic nature, therefore, large amounts of organic molecules such as pyrene were adsorbed from water based solution onto them. In addition to this, the intercalation compounds with long alkyl chains were soluble in organic solvents, forming so called nanosheet solution. This enabled to prepare thin film samples by casting the solution containing intercalation compounds and they can include various organic dyes between the alkyl chains. These alkyl chains well prevented the aggregation of dye molecules introduced into the layer of intercalation compounds. The fluorescence from organic dyes included in them increased by introducing perfluoroalkyl chains into them instead of alkyl chains.

Silylation of graphite oxide

Recently, much attention was paid to solid matrices for photochemical reaction media of organic molecules with specific selectivity [1–4]. These solids include layered materials, zeolites, etc. One of the layered materials, graphite oxides hydrophobized by intercalation of alkyltrimethylammonium ions or n-alkylamine have shown interesting properties when photochemical dimerization of acenaphthylene was performed in them [5–8]. These materials possess hydrophobic nanospace between the alkyl chains, which is suitable for including organic molecules [5–11]. It was proved that the size and polarity of the nanospace control the photochemical reaction of acenaphthylene [6–8]. However, these intercalation compounds were not so stable and released the alkylamine molecules gradually under ambient condition, though Bourlinos et al. have reported that alkylamine-intercalated GOs are stable even when they are in contact with sodium hydroxide solution [12]. The intercalation compounds of graphite oxide would be stabilized if the intercalated molecules are fixed in the interlayer space by covalent bonding. On the other hand, the silylation of the silanol groups in the interlayer space of a layered silicate using organochlorosilanes has recently been employed to construct novel inorganic– organic supramolecular systems [13–15]. A similar reaction is expected for graphite oxide because it possesses acidic hydroxyl groups on its layers. Therefore, in this study, silylation of graphite oxide was performed and the resulting product was investigated. Graphite oxide (GO) was prepared by oxidizing natural graphite powder with KClO3 in fuming nitric acid at 60 C, based on Brodie’s method [16]. Then the resulting solution was poured into a large excess of water and dried at 60 C. This procedure was repeated for 5 times and GO with the composition of C8O4:0H3:2 was obtained. It was silylated in a similar manner as reported by Ogawa et al for the silylation of a layered silicate. GO (400 mg) was mixed with butylamine (C4H9NH2, 2 ml) in a sealed glass vial under dry nitrogen and the resulting solution was sonicated, then heated at 60 C for 1 h. Dry toluene (water content <30 ppm, 20 ml) was added to this solution under a nitrogen atmosphere and the solution was again sonicated. Octyltrichlorosilane (C8H17SiCl3, in short C8SiCl, 2 ml) was added and then allowed to stand for 1 day. After centrifugation, the precipitate was washed with dry toluene, hexane, ethanol, acetone, the mixture of ethanol and water and finally acetone. The obtained sample was dried at 60 C under reduced pressure for 12 h. The composition of the product was determined on the basis of CHN elemental analysis. Octylamine-intercalated GO with a C8H17NH2/GO ratio of 1.2 was also prepared by reacting GO with octylamine in the presence of a small amount of hexane as reported previously, in order to compare the stability of the product in ethanol with that of the silylated GO. Fig. 1 shows the X-ray diffraction patterns of GO and silylated GO, together with that of butylamine-intercalated GO. The diffraction peak at 2h 1⁄4 14 derived of GO shifted to 6.5 for silylated GO, indicating an increase of the interlayer spacing by 0.75 nm. This increase of the interlayer spacing was much larger than that of butylamine-intercalated GO (0.28 nm). This suggests that C8SiCl with a long alkyl chain had reacted with GO and was intercalated into its interlayer spacing of GO. Fig. 2 shows the IR spectra of GO, butylamineintercalated GO and silylated GO. Strong absorption peaks around 2900, 1450, 1150 and 850 cm 1 were observed after reaction with C8SiCl. The latter two peaks were absent in butylamine-intercalated GO. These would be due to –CH2–, CH3, Si–O and Si–C groups, respectively. On the other hand, the absorption peaks at 1620 and 1380 cm 1 ascribed to adsorbed water and COH groups became relatively smaller. This indicates that C8SiCl reacted with GO, losing chlorine and was covalently bonded to the GO layer by Si–O bonding. The elemental analysis data showed that the silylated product contained 60.32% of carbon, 5.25% of hydrogen and 1.32% of nitrogen. A similar product was obtained when GO was reacted with C8H17SiCH3Cl2, however, reaction

Influence of Organic and Inorganic Salts on the Coagulation of Montmorillonite Dispersions

AbstractThe colloidal state (stable, coagulated, or gel-like) and the rheological properties of Na-rich montmorillonite (Wyoming) dispersions are strongly influenced by organic cations. This effect is shown for homologous organic cations: alkyl trimethylammonium ions, paraquat, diquat, alkyl bispyridinium ions, and the triphenylmethane dyes crystal violet, methyl green, and tris (tri-methylammonium phenyl) methane chloride. The critical coagulation concentrations, cK, are small (often &lt; 1 mmol/L) because the cations are enriched in the Stern layer and influence the solvent structure near the surface. The strong adsorption of the counterions at the clay-mineral surface causes cK values to increase with the solid content. Charge reversal (recharging) of the particles was observed with the longer chain alkyl trimethyl-ammonium ions, dodecyl bispyridinium ions, and crystal violet. Other cations reduced the electrophoretic mobility to zero but positive particle charges were not observed.The plastic viscosity increased sharply at the critical coagulation concentration and showed a minimum slightly below cK, which was caused by the electroviscous effect. Yield values were developed at concentrations above cK. In most cases, yield values reached a plateau where the amount of organic cations was ∼0.5 mmol/g, i.e., about half of the cation-exchange capacity. The cK values decreased with increasing hydrophobicity of homologous compounds, but the yield value showed maxima at intermediate chain lengths. The yield value of several 0.5% dispersions was high, e.g., dodecyl trimethylammonium ions, 71 Pa; paraquat, 100 Pa; diquat, 42 Pa; hexyl bispyridinium ions, 53 Pa (vs. Ca2+, 0.2 Pa; Al3+, 0.7 Pa). The storage modulus as a function of the number of organic cations changed in a similar way as the yield value, and high values were observed (e.g., dodecyl trimethylammonium ions, hexyl bispyridinium ions: 1000 Pa, paraquat: &gt;4000 Pa). Thus, dispersions with high viscosity, yield value, and pronounced viscoelasticity are obtained by coagulating Na-rich montmorillonite dispersions with organic cations.

Smoothing of the thermal stability of DNA duplexes by using modified nucleosides and chaotropic agents.

The effect of alkyltrimethylammonium ions on the thermostability of natural and modified DNA duplexes has been investigated. We have shown that the use of tetramethylammonium ions TMA+along with the chemical modification of duplexes allow the fine adjustment of T m and the possibility of obtaining several duplex systems with varied isostabilizedtemperatures, some of which show greater stability than those of natural DNA. This approach could be very useful for DNA sequencing by hybridization.

Volumetric properties and compressibilities of alkyltrimethylammonium bromides and sodium alkylsulphates in aqueous solution

Density and sound velocity data for aqueous solutions at 298.2 K containing alkyltrimethylammonium bromides and sodium alkylsulphates were analysed to yield partial molar volumes and isentropic compressions. The calculated contributions of methylene groups to the properties of alkyltrimethylammonium cations and alkylsulphate anions show no dependence on position in the alkyl chains and a common contribution to the ionic partial molar volumes over the range methyl ≤ n-octyl for the sulphates and n-propyl ≤ n-hexyl for the alkyltrimethylammonium ions. However, a switch in head group from trimethylammonium to sulphate changes the contribution of methylene groups to estimated partial molar isentropic compressibilities. The reasons for this sensitivity are discussed in terms of hydration characteristics. © 1998 John Wiley & Sons, Ltd.

Volumetric properties and compressibilities of alkyltrimethylammonium bromides and sodium alkylsulphates in aqueous solution

Density and sound velocity data for aqueous solutions at 298.2 K containing alkyltrimethylammonium bromides and sodium alkylsulphates were analysed to yield partial molar volumes and isentropic compressions. The calculated contributions of methylene groups to the properties of alkyltrimethylammonium cations and alkylsulphate anions show no dependence on position in the alkyl chains and a common contribution to the ionic partial molar volumes over the range methyl ≤ n-octyl for the sulphates and n-propyl ≤ n-hexyl for the alkyltrimethylammonium ions. However, a switch in head group from trimethylammonium to sulphate changes the contribution of methylene groups to estimated partial molar isentropic compressibilities. The reasons for this sensitivity are discussed in terms of hydration characteristics. © 1998 John Wiley & Sons, Ltd.

Silica-based mesoporous molecular sieves derived from a layered polysilicate kanemite?A review

Synthesis of highly ordered mesoporous materials derived from a layered polysilicate kanemite has been reviewed. Silica-surfactant mesostructured materials are obtained by the reaction of kanemite with alkyltrimethy lammonium ions. Calcination of silica-surfactant mesophase materials yields ordered mesoporous molecular sieves. Substantial replacement of alkyltrimethylammonium ions for interlayer Na ions and careful adjustment of pH in the reaction media are necessary for the preparation of ordered mesoporous silica. Formation processes of the silicate-surfactant mesophase materials have been monitored by in-situ powder X-ray diffraction technique which has indicated the presence of a lamellar phase before the appearance of a hexagonal phase. Comparison of these materials with MCM-41 is briefly mentioned. The properties and potential applications of these materials are also briefly outlined.

Polarization and impedance studies on the effects of anion and cation inhibitors on corrosion of iron in an electrolytic anhydrous methanol solution of ferric chloride

Inhibition mechanisms of anionic and cationic inhibitors for corrosion of iron in an anhydrous methanol solution of 0.1M LiClO 4 and 0.01M FeCl 3 (H 2O < 80 ppm) were investigated by polarization and impedance measurements of an iron electrode, the surface of which was prepared under an argon atmosphere in a dry box. Because of specific adsorption on the surface, Br − mostly suppressed the anodic Cl −catalyzed iron dissolution. The cathodic process, reduction of Fe 3+ to Fe 2+, was mainly inhibited by adsorption of alkyltrimethylammonium ion C n TMA + via an electrostatic interaction between the cation and the negatively charged surface. Joint adsorption of Br − and C n TMA + on the surface results in synergistic inhibition of both processes. Iodide ion was less effective for iron corrosion in the FeCl 3 methanol solution than Br −because of I −oxidation with Fe 3+ to form I 3 −. Thiocyanate ion stimulated the anodic iron dissolution process through a SCN −-catalyzed path.