Alkyltrimethylammonium Salts Research Articles

Mechanical Properties of Molecular Assemblies of Cationic Amphiphiles Adsorbed at Solid/Liquid Interfaces

The aggregates properties of amphipathic molecules formed at solid-liquid interfaces are influenced by the environmental conditions: solution concentration, temperature, kind of counterion, etc. The effect of the counterions on the adsorbed aggregates was investigated by atomic force microscopy in surface force mode and in surface imaging mode for alkyltrimethylammonium salts (hexadecyltrimethylammonium bromide; CTABr, hexadecyltrimethylammonium chloride; CTACl) at silica-aqueous solution interfaces. The surface force data was analyzed by using DLVO theory. The aggregate of CTABr had smaller surface potential than that of CTACl, and thus, the dissociation degree for CTABr aggregate was lower than that for CTACl. The collapse pressure for CTABr aggregate was smaller than that for CTACl. Although adsorbed aggregates with circular projections were observed for both CTABr and CTACl, the diameter of the circles for CTABr was greater than that for CTACl. Therefore, the aggregates of CTABr on the surface were softer and larger than those of CTACl. It will be considered that the aggregates of CTABr and CTACl were formed with a hemimicelle adsorbed on a flat monolayer and an admicelle on a solid surface, respectively.

Assessment of the Biodegradability of Dialkyldimethylammonium Salts in Flow Through Systems

A bacterium capable of utilizing the alkyl chains of didecyldimethylammonium salt was isolated from activated sludge. In addition, the isolate also utilized didodecyldimethylammonium salt, ditetradecyldimethylammonium salt and alkyltrimethylammonium salts (C10 to C18) as sole source of carbon and energy. The broad substrate with respect to the alkyl chain length was also demonstrated with oxidation rates of various quaternary ammonium salts by didecyldimethylammonium chloride-grown cells. The oxidation rate decreased with increasing alkyl chain lengths. The main factor impeding the biodegradation of dialkyldimethylammonium salts with long alkyl chains is probably the low bioavailability of water-insoluble chemicals. The biodegradability of dialkyldimethylammonium salts was therefore determined in flow-through columns at concentrations below their aqueous solubility. Dialkyldimethylammonium salts adsorbed on silica gel particles packed in flow-through columns were immediately metabolized by the isolate when dissolved. Microorganisms present in river water pumped through a sterile column degraded dissolved dicocodimethylammonium salts within a week.

Application of polyelectrolyte complexes as novel pseudo-stationary phases in MEKC.

Polyacrylic acid (PAA) and polymethacrylic acid (PMAA) with carboxyl groups partially blocked by dodecyltrimethylammonium bromide (DTAB) and tetrabutylammonium bromide (TBAB) were tested as new pseudo-stationary phases in micellar electrokinetic chromatography (MEKC). The separation of was examined using PAA and PMAA. Excellent resolution of the substituted phenols and derivatized amino acids was demonstrated using additives of PAA-DTAB polyelectrolyte complex in the running phosphate buffer. It was found that the capacity factors were proportional to the concentration of the complex PAA/DTAB. Critical micelle concentration was effectively zero. It was found that the migration times and efficiency of separation of phenols and derivatives of amino acids depended on the type of polymers and alkyltrimethylammonium salts used.

Macroporous Silica and Alkylene-Bridged Polysilsesquioxane Gels with Templated Nanopores

ABSTRACTGels with hierarchical well-defined macropores and supramolecularly templated mesopores have been synthesized in the systems of pure silica as well as organic-inorganic hybrids. Cationic surfactants such as alkyltrimethylammonium salts and nonionic surfactants such as poly(ethyleneglycol)-poly(propyleneglycol)- poly(ethyleneglycol) triblock copolymers, EOPOEO, were found to be effective for pure silica system both in inducing the phase separation to give macroporous morphology and in templating the mesopores within a narrow distribution width. The partial introduction of methyl-modified alkoxide into the pure silica system lead to increased phase separation tendency accompanied by the disturbance of the supramolecular templating of mesopores. By contrast, in the 1,2-bis(trimethoxysilyl)ethane systems, poly(ethylene glycol) and EOPOEO were much better additive to induce phase separation in spite of the presence of internal hydrocarbon chain. Combination of well-defined macropores and supramolecularly templated mesopores has been achieved by selecting an appropriate molecular weight and concentration of EOPOEO in the starting composition.

Multiple linear regression modeling of the critical micelle concentration of alkyltrimethylammonium and alkylpyridinium salts

AbstractThe critical micelle concentration (CMC) of a set of 30 alkyltrimethylammonium [RN+(R′)3X−] and alkylpyridinium salts [RN+ΦX−] was related to topological, electronic, and molecular structure parameters using a stepwise regression method. Among different models obtained, two equations were selected as the best and their specifications are given. The statistics for these models together with the crossvalidation results indicate the capability of both models to predict the CMC of cationic surfactants. The results obtained for alkyltrimethylammonium salts indicate that geometric characteristics such as volume of the tail of the molecule, maximum distance between the atoms, and surface area play a major role in micelle formation. However, the simultaneous modeling of the CMC of both alkyltrimethylammonium and alkylpyridinium salts indicates that the topological descriptors of the Balaban and Randic indices and also the electronic parameter of total energy of the molecules are important.

Supramolecular templating of mesopores in phase-separating silica sol-gels incorporated with cationic surfactant

Silica gels with hierarchical macropores and mesopores have been prepared by inducing phase separation in the alkoxide-based sol-gel system with an addition of alkyltrimethylammonium salt. Narrowly distributed mesopores were observed in the heat-treated gel samples possibly as a result of supramolecular templating of silica oligomers in the reacting solution. The ionic attractive interaction and hydrophobicity of the attached alkyl group cooperatively determined the phase separation tendency. No indication of long-range order of the mesopores was obtained.

Mesostructured vanadium-phosphorus-oxide phases

Ordered mesostructured hexagonal, cubic and lamellar vanadium-phosphorus-oxide phases displaying improved thermal stability, desirable bulk compositions, and vanadium oxidation states (3.8–4.3) for the partial oxidation of lower alkanes were synthesized using cationic (alkyl trimethyl ammonium salts), anionic (alkyl sulfonates and phosphates) and primary alkylamines as structure-directing agents. It was found that hexagonal mesophases were favored at short carbon chain lengths (C 12–C 16), while cubic phases were favored for longer chains (C 18). Structure-directing agents were removed by calcination or Soxhlet extraction in ethanol. When structure-directing agents were removed by extraction, phase transformations from hexagonal to cubic to lamellar structures were observed. The improved thermal stability of these mesophases was attributed to the acidic self-assembly conditions in the vicinity of the isoelectric point of V(V) oxocations.

Lyotropic Liquid-Crystalline Phase Behavior of Some Alkyltrimethylphosphonium Bromides

The lyotropic liquid crystal (LLC) behavior of a homologous series of alkyltrimethylphosphonium bromide salts is described. While alkyltrimethylammonium salts are common LLC mesogens that have served in mesoporous materials, phase-transfer catalysis, and polymer−surfactant assemblies, the LLC behavior of the analogous phosphonium salts has been relatively unexplored. Dodecyl- (C12TMPB), tetradecyl- (C14TMPB), and hexadecyltrimethylphosphonium bromide (C16TMPB) were found to exhibit hexagonal, lamellar, and cubic mesophases similar to their ammonium counterparts; however, there is a key difference: Changing to a phosphorus-based headgroup appears to stabilize the cubic phase of C12TMPB and C14TMPB such that the phases extend down to room temperature. Some trends in the lattice parameters of the resulting LLC phases of the alkyltrimethylphosphonium bromides with respect to phase composition and temperature are also discussed. Finally, preliminary use of 31P NMR spectroscopy, as a method of structural chara...

Determination of perchlorate at trace levels in drinking water by ion-pair extraction with electrospray ionization mass spectrometry.

Perchlorate has been added to the U.S. Environmental Protection Agency's Drinking Water Contaminant Candidate List (CCL). The present work describes the analysis of perchlorate in water by liquid-liquid extraction followed by flow injection electrospray mass spectrometry (ESI/MS). Cationic surfactants, mostly alkyltrimethyl-ammonium salts, are used to ion-pair aqueous perchlorate, forming extractable ion pairs. The cationic surfactant associates with the perchlorate ion to form a complex detectable by ESI/MS. The selectivity of the extraction and the mass spectrometric detection increases confidence in the identification of perchlorate. The method detection limit for perchlorate based on 3.14 sigma n-1 of seven replicate injections was 100 ng L-1 (parts per trillion). Standard addition was used to quantitate perchlorate in a drinking water sample from a contaminated source, and the concentration determined agreed within experimental error with the concentration determined by ion chromatography.

Preparation of Mesostructured Materials from Tetramethoxysilane and Alkyltrimethylammonium Salts and Their Conversion to Porous Silica

A novel synthetic route for the preparation of the porous silica by a supramolecular templating mechanism is reported. By depositing the precursor solution containing tetramethoxysilane and hexadecyltrimethylammonium chloride on glass plates at an elevated temperature (60°C), mesostructured silica-hexadecyltrimethylammonium chloride composites with the size of a few mm to a cm have been prepared. The composition of the resulting products can be controlled by simply changing the composition of the starting mixtures. By the calcination of the as synthesized mesostructured materials, porous silica with large surface area was obtained. Due to the ease of operation, the present method is a simple way to prepare porous silica alternative to the procedures reported for the preparation of mesoporous silicas (MCM-41 and FSM-16).

Layered Alkyltrimethylammonium Chromates: Thermal and Structural Investigations and Crystal Structure of the Anhydrous Bisoctyltrimethylammonium Dichromate

New mesostructured bisalkyltrimethylammonium dichromates of formula (CnH2n+1(CH3)3N)2Cr2O7·xH2O (n=12, 14, 16, 18; 0≤x≤2) were prepared at 80°C from an aqueous solution of alkyltrimethylammonium salt and K2Cr2O7. The chemical composition and phase transitions have been determined by thermogravimetric analysis (TGA) coupled with differential scanning calorimetry (DSC) and mass spectrometry (MS). As suggested by X-ray diffraction and transmission electron microscopy studies, the lamellar hydrated and anhydrous bisalkyltrimethylammonium dichromates crystallize in the triclinic system, with space groupP-1. The structure of the anhydrous bisoctyltrimethylammonium dichromate, (C18H37(CH3)3N)2Cr2O7, was determined from single-crystal X-ray diffraction data. The compound crystallizes in the triclinic system, space groupP-1, with 2 formula units in a cella=7.197(1) Å,b=8.816(2) Å,c=43.400(9) Å,α=93.43(3)°,β=90.00(3)°,γ=113.98(3)°. The structure consists of discrete dichromate anions stacking up in a layer, separated by a double layer of octyltrimethylammonium surfactant chains lying in parallel. The interlayer spacing of 43.4 Å, smaller than the expected value for the fully extended molecular model, is achieved through a tilting of the surfactant chains of about 37.5° from the normal to the (Cr2O7)2−plane.

Preparation of transparent thin films of silica-surfactant mesostructured materials

Our recent studies on the simple synthetic route to the thin films of the periodic silica-surfactant mesostructured materials are summarized. By depositing the mixtures of the prehydrolyzed tetramethoxysilane and alkyltrimethylammonium salts under anacidic condition on solid supports, transparent thin films of the periodic silica-surfactant mesostructured materials formed. The resulting transparent films have been used as a precursor of the porous silica films and a support for organic photoactive species. Compared with other reported reactions for the silica-surfactant mesostructured materials, this method possesses advantages such as the ease of operation and the possibility to control microstructure and macroscopic morphology.

Spectrophotometric determination of cationic surfactants in water samples containing anionic surfactants.

Concerning the spectrophotometric determination of cationic surfactants (CS) with anionic dyes, when a large amount of anionic surfactants (AS) is contained in a water sample, CS can not be determined, because it reacts with AS to form a CS-AS ion associate and doesn't react with anionic dyes. A method is proposed to avoid interference from AS based on the extraction of the CS-AS ion associate formed into an organic solvent from water samples to separate it from any excess of AS and color development by replacing AS in the CS-AS ion associate extracted with anionic dyes. In the presence of dodecylsulfate (LAS) as AS and sodium chloride, CS, such as alkyl trimethyl ammonium salts, tetraalkyl ammonium salts, alkyl dimethyl benzyl ammonium salts and alkyl pyridinium salts, was extracted as the CS-AS ion associate into 1, 2-dichloroethane. When a tetrabromophenolphtalein ethylester dye anion (TBPE) was used at pH8.510 as anoinic dyes, a CS-TBPE ion associate was formed in 1, 2-dichloroethane and was measured spectrophotometrically at 610 nm. The absorbance was propotional to the concentration of CS. Good results were obtained on recovery tests using river and sea water samples containing AS in the range of 0.120.16 mg as LAS/1.

Preparation of transparent mesoporous silica films by a rapid solvent evaporation method

Thin films of silica-alkyltrimethylammonium (alkyl=decyl, dodecyl, tetradecyl, hexadecyl and octadecyl) chloride mesostructured materials are synthesized by spin coating the precursor solutions containing prehydrolyzed tetramethoxysilane and alkyltrimethylammonium salts. The films have been converted to transparent porous silica films by calcining in air. Cationic dyes, Methylene Blue, 1,1-diethyl-2,2-cyanine, tetrakis(N-methyl-4-pyridinio)porphyrin, have been adsorbed on the porous films to give colored films. The preparation of the self-standing film of the silica-hexadecyltrimethylammonium chloride mesostructured material by using poly(methyl methacrylate) coated glass substrate is also reported.

Effect of delayed neutralization on the synthesis of mesoporous MCM-41 molecular sieves

We present a detailed study on the preparation of highly-ordered MCM-41 molecular sieves based on a new delayed neutralization process. Products synthesized from cationic surfactants with different carbon chain lengths (alkyltrimethylammonium salt), counterions and head groups gave almost constant wall thickness (about 1.7nm), small lattice contraction after calcination, and sharp pore size distribution. However, the structural order decreased with the decrease of the carbon chain length. Adding a proper amount of alcohols as cosurfactants would improve the XRD patterns of the surfactants with carbon chain lengths less than 14. A head group of larger size would shrink the pore size and damage somewhat the structural order of MCM-41 materials. The rate of acidification and the source of the acid did not have much effect on the XRD patterns of MCM-41, but would affect its morphology. The formation process and the nature of the MCM-41 product based on octadecyltrimethylammonium bromide (C 18TMAB) are dependent on the synthetic temperature.

Hydrophobic interactions are involved in the inhibition of human leukocyte elastase by alkyltrimethylammonium salts

Electrostatic forces and hydrophobic interactions had been suggested to modify the adsorption of elastases onto insoluble fibrous elastin, which is the initial stage of elastolysis, but conflicting results had been obtained, and comparison between compounds with different structures was difficult. In order to explore these observations, we have studied the effect of six alkyltrimethylammonium bromides, with alkyl chain length ranging from six to 16 carbon atoms, on human leucocyte elastase activities, either with a synthetic substrate or with insoluble elastin. The enzymatic studies were performed either spectrophotometrically or using conductimetry, and direct binding on to elastin was conductimetrically measured. Binding of the alkyltrimethylammonium salts is increasing with alkyl chain length and we could demonstrate a cooperative binding for tetra- and hexadecyl chains. No effect of the six compounds could be evidenced on hydrolysis of a specific synthetic substrate. With insoluble elastin, elastolysis inhibition could be demonstrated for alkyl chain longer than ten carbon atoms, the effect increasing with chain length. A similar inhibition was observed with the soluble κ-elastin, but it was less effective. The study shows that the interaction between the alkyltrimethylammonium salts and elastin plays a major role in the inhibitory potency of these molecules. As this effect is enhanced with alkyl chain length, it was concluded that hydrophobic interactions favour their binding, protecting elastin against elastase adsorption.

A modification of receptor theory. 1956.

A modification of receptor theory. 1956.

Complete degradation of xenobiotic surfactants by consortia of aerobic microorganisms

Linear alkylbenzene sulphonates are primarily attacked via a hydroxylation of the alkyl chain from the methyl group followed by beta-oxidation. The alkyl chain is metabolized by pure cultures to give sulphophenyl carboxylates which accumulate in the medium. In mixed culture, other microorganisms are capable of degrading sulphophenyl carboxylates. Formation of ethylene glycol monosulphates as major products of alkyl ethoxy sulphates demonstrates that the ether bonds are cleaved. The bacteria involved in growing on the alkyl chain are unable to utilize the hydrophilic moiety. This hydrophilic moiety, in turn, is degraded by other microorganisms. The degradation of alkylphenol ethoxylates and highly branched alcohol ethoxylates proceeds by shortening the polyoxyethylene chain leaving the hydrophobic part of the molecule. The biodegradation of linear alcohol ethoxylates and ethoxylated fatty amines is initiated by a central cleavage or omega-oxidation. Subsequent oxidation of the alkyl chains results in the production of polyethylene glycols and secondary ethoxylated amines. Both polar moieties are metabolized by other microorganisms. Degradation of alkyltrimethylammonium salts and alkylamines is initiated by a cleavage of the Calkyl-N bond. The central fission leads to the formation of alkanals which are readily converted by beta-oxidation. The alkyl chain-utilizing bacteria are not able to degrade the methylamines. The methylamines, in turn, are subject to biodegradation by methylotrophs. The limited metabolic capacities of pure cultures of microorganisms utilizing surfactants point to the requirement of consortia to degrade surfactants completely. Complete degradation of surfactants is accomplished by mixed cultures of microorganisms constructed on the basis of synergistic and commensalistic relationships. However, degradation of a surfactant by one member of a commensalistic consortium may lead to the production of toxic or non-toxic metabolites. Waste water treatment without the build up of such metabolites can be achieved in plants operated with sludge retention times that are suitable for maintaining all microorganisms of the consortium. In contrast, in natural ecosystems the introduction of a surfactant may result in a transient formation of a metabolite.

Formation of a Porous Zirconium Oxo Phosphate with a High Surface Area by a Surfactant‐Assisted Synthesis

Analogous to the synthesis of MCM-41, a mesostructured product (shown schematically on the right) can be obtained from aqueous solutions of zirconium sulfate by addition of alkyltrimethylammonium salts. After a treatment with phosphoric acid, this material can be calcined without structural collapse. The resulting zirconium oxo phosphate shows BET surface areas of up to 400 m2 g−1.

A simple sol–gel route for the preparation of silica–surfactant mesostructured materials

Hexagonal silica–surfactant nanocomposite films are successfully prepared by a novel sol–gel process in which alkyltrimethylammonium salts are directly dissolved into pre-hydrolysed tetramethoxysilane.