Sorption of Bisphenol A as Model for Sorption Ability of Organoclays

The arrangement of bisphenol A molecules into organoclays and their interactions with the intercalated surfactant were studied. The organoclays were prepared via solid-state intercalation of four cationic surfactants, such as dodecyltrimethyl-, tetradecyltrimethyl-, hexadecyltrimethyl-, and didodecyldimethyl-ammonium, as bromide salts, at different loading levels into the interlayers of two natural clays. The natural clays, the prepared organoclays, and the spent organoclays were characterized by X-ray powder diffraction, infrared spectroscopy, and scanning electron microscopy. X-ray powder diffraction measurements showed successive interlayer expansions of the d₀₀₁ basal spacing due to the intercalation of the cationic surfactants and the bisphenol A sorption. The increased d₀₀₁ basal spacing of the organoclays after bisphenol A sorption indicates that the molecules are integrated between the alkyl chains of the surfactant in the organoclays interlayers. Infrared spectroscopy was employed to probe the intercalation of the cationic surfactants and the sorbed bisphenol A. New characteristic bands attributed to the bisphenol A phenol rings appear in the range 1518–1613 cm⁻¹ on the infrared spectra of the spent organoclays, proving the presence of bisphenol A in the hydrophobic interlayers. Scanning electron microscopy of the organoclays before and after BPA sorption shows that their morphology becomes fluffy and that the presence of the organic molecules expands the clay structure.     

The photodimerization of a cinnamoyl moiety derivative in dilute solution based on the intramolecular chain interaction of gemini surfactant

A Gemini surfactant, sodium N, N'-di(4-n-butyloxy cinnamoly)-L-cystine, containing a cinnamoyl moiety in the alkyl chains and disulfide bond in the spacer was designed and synthesized. The incorporation of a cinnamoyl moiety into the alkyl chains of Gemini surfactant makes it easy to probe the conformational information of the amphiphile molecule. The UV/vis absorption spectra and steady-state fluorescence were investigated at a concentration far below the critical micelle concentration (cmc). Both blue-shift of absorption and red-shift of fluorescence emission spectra indicate the existence of intramolecular interaction between the two alkyl chains in Gemini surfactant in the singly dispersed state. Results based on the breakdown of the disulfide bond by dithiotheritol (DTT) further confirmed the conclusion. Moreover, the characteristic of intramolecular chain interaction in Gemini surfactant improves the topochemical geometrical requirements of cinnamoyl moiety and increases the local concentration of reactant in dilute solution. Utilizing the incorporation of cinnamoyl moiety into the alkyl chains of Gemini surfactant, the cinnamoyl moiety upon irradiation undergoes dimerization in dilute aqueous solution with high yield of 78%.     

Adsorption of p-nitrophenol on organoclays

In this study, organoclays were prepared through ion exchange of a single cationic surfactant, hexadecyltrimethylammonium bromide and characterised by a range of methods including X-ray diffraction (XRD) and thermogravimetric analysis. Changes in the surface properties of montmorillonite and the organoclays were observed and the basal spacings of organoclays with and without p-nitrophenol were determined using XRD. The thermal stability of both organoclays were measured using thermogravimetry. As the surfactant loading increased, the expanded basal spacings were observed, and different molecular configurations of surfactant were identified. When the surfactant loading exceeded 1.0 CEC, surfactant molecules tend to adsorb strongly on the clay surface and this resulted in increased affinity to organic compounds. The adsorbed p-nitrophenol and the surfactant decomposed simultaneously. Hence, the surfactant molecules and adsorbed p-nitrophenol are important in determining the thermal stabilities of organoclays. This study enhances the understanding of the structure and adsorption properties of organoclays and has further implications for the application of organoclays as filter materials for the removal of organic pollutants in aqueous solutions.     

Synthesis and surface activity of mono- and diphosphate ester mixture with different alkyl chain length

A series of alkyl phosphate esters were synthesized and each of them was a mixture of monophosphate and diphosphate esters in a high or low mono/dimole ratio. The structure of hexadecyl phosphate ester with a low mono/dimole ratio was confirmed by FTIR, ¹H NMR, and³¹P NMR. The surface tensions of these alkyl phosphate esters were analyzed using a surface tensionmeter. The results showed that the critical micelle concentration (CMC) and critical surface tension (γ_CMC) of phosphate esters with a high mono/di ratio decreased with the increase of alkyl chain length. However, for the phosphate esters with a low mono/di ratio, the CMC, and γ_CMC decreased initially and increased afterwards with the increase of alkyl chain length. Meanwhile, the butanol and octanol phosphate esters with a high mono/di ratio had higher CMC and γ_CMC than their low mono/di ones, while the dodecyl and hexadecyl phosphate esters presented an opposite result. The results indicated that the mono- and diphosphate esters in the mixture may have a synergistic effect on the arrangement of molecules.     

Characterization and application of sodium di(2-ethylhexyl) sulfosuccinate and sodium di(2-ethylhexyl) phosphate surfactants as pseudostationary phases in micellar electrokinetic chromatography

Sodium di(2-ethylhexyl) sulfosuccinate (DOSS) and sodium di(2-ethylhexyl) phosphate (NaDEHP) surfactants, with double alkyl chains and negatively charged headgroups, were characterized using fluorescence quenching, densitometry, and tensiometry techniques to determine their aggregation number, partial specific volume, and critical aggregation concentration. These two surfactants were then applied as pseudostationary phases in micellar electrokinetic chromatography (MEKC) for separations of alkyl phenyl ketones. The aggregation number of NaDEHP was found to be more than two-fold higher than that of DOSS. The partial specific volumes of NaDEHP and DOSS were found to be 0.9003 and 0.8371 mL/g, respectively. The critical aggregation concentrations are 5.12 and 1.80 mM for NaDEHP and DOSS, respectively. The DOSS surfactant provided a wider separation window and had a greater hydrophobic environment than the NaDEHP surfactant under the MEKC experimental conditions studied.     

Mono,di, tri and tetraethylene glycol: Spectroscopic characterization using density functional method and experiment

We report infrared and electronic absorption spectra of mono, di, tri and tetra ethylene glycol (EG) in gas phase, their cation and anion and in water solvent using density functional theory calculations at B3LYP/TZVP level. Structural paramaters, rotational and centrifugal distortional constants and dipole moments are also reported. A siginificant shifts in vibrational frequencies and peaks in electronic absorption spectra have been observed upon ionization of mono, di, tri and tetra ethylene glycols. We have also obtained experimental vibrational spectrum of monoethylene glycol. Vibrational frequencies of mono ethylene glycol from theory and experiment are compared. We have used integral equation formalism polarizable continuum model (IEFPCM) model to study the influence of water solvent on vibrational frequencies of neutral mono, di, tri and tetra ethylene glycol. Electronic absorption spectra for these molecules have been obtained using Time dependent density functional theory (TDDFT).     

Solution properties of mixed surfactant systems (IV)

Electric properties of mixed anionic-nonionic surfactant systems in aqueous solutions above the CMC have been studied in terms of pNa values, electrical conductivities, and dielectric constants; these systems are sodium 3, 6, 9-trioxaicosanoate (ECL) — alkyl polyoxyethylene ethers (C_mPOE; m=12, 14, 16, and 18). The degree of ionic dissociation of mixed micelle increases with increasing the number of carbon atoms of the alkyl group in the nonionic surfactant. The electrical conductivity increases with increasing the alkyl chain length in the nonionic surfactant, in spite of the increase of the activation energy for conduction. The size of mixed micelles also increases with increasing alkyl chain length. This may be attributed to the fact that the mixed micelle is formed more easily by a nonionic surfactant including long alkyl chains than for one having shorter alkyl chains.     

Radical CH Alkylation of BODIPY Dyes Using Potassium Trifluoroborates or Boronic Acids

A one‐step synthetic procedure for the radical C?H alkylation of BODIPY dyes has been developed. This new reaction generates alkyl radicals through the oxidation of boronic acids or potassium trifluoroborates and allows the synthesis of mono‐, di‐, tri‐, and tetraalkylated fluorophores in a good to excellent yield for a broad range of organoboron compounds. Using this protocol, multiple bulky alkyl groups can be introduced onto the BODIPY core thus creating solid‐state emissive BODIPY dyes.     

Modification of Wyoming montmorillonite surfaces using a cationic surfactant

Surfaces of Wyoming SWy-2-Na-montmorillonite were modified using ultrasonic and hydrothermal methods through the intercalation and adsorption of the cationic surfactant octadecyltrimethylammonium bromide (ODTMA). Changes in the surfaces and structure were characterized using X-ray diffraction (XRD), thermal analysis (TG), and electron microscopy. The ultrasonic preparation method results in a higher surfactant concentration within the montmorillonite interlayer when compared with that from the hydrothermal method. Three different molecular environments for surfactants within the surface-modified montmorillonite are proposed upon the basis of their different decomposition temperatures. Both XRD patterns and TEM images demonstrate that SWy-2-Na-montmorillonite contains superlayers. TEM images of organoclays prepared at high surfactant concentrations show alternate basal spacings between neighboring layers. SEM images show that modification with surfactant reduces the clay particle size and aggregation. Organoclays prepared at low surfactant concentration display curved flakes, whereas they become flat with increasing intercalated surfactant. Novel surfactant-modified montmorillonite results in the formation of new nanophases with the potential for the removal of organic impurities from aqueous media.     

Effects of organoclays on morphology and thermal and rheological properties of polystyrene and poly(methyl methacrylate) blends

Morphology, thermal and rheological properties of polymer‐organoclay composites prepared by melt‐blending of polystyrene (PS), poly(methyl methacrylate) (PMMA), and PS/PMMA blends with Cloisite® organoclays were examined by transmission electron microscopy, small‐angle X‐ray scattering, secondary ion mass spectroscopy, differential scanning calorimetry, and rheological techniques. Organoclay particles were finely dispersed and predominantly delaminated in PMMA‐clay composites, whereas organoclays formed micrometer‐sized aggregates in PS‐clay composites. In PS/PMMA blends, the majority of clay particles was concentrated in the PMMA phase and in the interfacial region between PS and PMMA. Although incompatible PS/PMMA blends remained phase‐separated after being melt‐blended with organoclays, the addition of organoclays resulted in a drastic reduction in the average microdomain sizes (from 1–1.5 μm to ca. 300–500 nm), indicating that organoclays partially compatibilized the immiscible PS/PMMA blends. The effect of surfactant (di‐methyl di‐octadecyl‐ammonia chloride), used in the preparation of organoclays, on the PS/PMMA miscibility was also investigated. The free surfactant was more compatible with PMMA than with PS; the surfactant was concentrated in PMMA and in the interfacial region of the blends. The microdomain size reduction resulting from the addition of organoclays was definitely more significant than that caused by adding the same amount of free surfactant without clay. The effect of organoclays on the rheological properties was insignificant in all tested systems, suggesting weak interactions between the clay particles and the polymer matrix. In the PS system, PMMA, and organoclay the extent of clay exfoliation and the resultant properties are controlled by the compatibility between the polymer matrix and the surfactant rather than by interactions between the polymer and the clay surface. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 44–54, 2003     

Characterization of Heterogeneous Interaction Behavior in Ternary Mixtures by a Dielectric Analysis: Equi-Molar H–bonded Binary Polar Mixtures in Aqueous Solutions

The heterogeneous associating behavior of the aqueous binary mixtures of ethyl alcohol, ethylene glycol, glycerol and mono alkyl ethers of ethylene glycol, and aqueous ternary mixtures of equi-molar binary systems (i.e., mono alkyl ethers of ethylene glycol with ethyl alcohol, ethylene glycol and glycerol) have been investigated over the entire concentration range using accurately measured dielectric constants at 25 ^∘C. The concentration dependent values of the excess dielectric parameter ε^E and effective Kirkwood correlation factor g ^eff were determined using the measured values of the static dielectric constant, ε_o, at 1 MHz and the high frequency limiting dielectric constant ε_∞ = n _D ². The observed ε^E values in aqueous binary and ternary mixtures are negative over the entire concentration range, which implies the formation of heterogeneous complexes between these molecules that reduces the effective number of dipoles. The stoichiometric ratio corresponding to the maximum interaction in alcohol + water mixtures increases with an increase in the number of hydroxyl groups of the alcohol molecules, but for mono alkyl ethers of ethylene glycol + water mixtures it decreases with the increase in the molecular size of the mono alkyl ethers. In aqueous ternary mixtures the stoichiometric ratio for the maximum extent of heterogeneous interaction is governed by the molecular size of the mono alkyl ethers. It was also found that the strength of the heterogeneous H–bond connectivities in the water + alcohol systems decrease with an increase in the number of hydroxyl groups of the alcohol molecules. However in the case of water + mono alkyl ether binary mixtures and in ternary mixtures, the strength of H–bond connectivities increases with the increase in the molecular size of the mono alkyl ether. An analysis of the g ^eff values confirms that the heterogeneous interaction involves the orientation of molecular dipoles in the studied systems.     

Studies of Synergism/Antagonism in Sodium Alkyl Benzene Sulfonate/Methyl Oleate Model Oil Systems

Experimental studies are conducted in order to elucidate the mechanisms responsible for synergism/antagonism for lowering interfacial tension in alkyl benzene sulfonate/brine/methyl oleate model oil and alkyl benzene sulfonate/alkali/methyl oleate model oil systems. We found that different mechanisms exist in above two systems. In alkyl benzene sulfonate/brine/methyl oleate model oil systems, methyl oleate influences the partition of added surfactants between oil and aqueous phase by changing equivalent alkane carbon number (EACN) value of model oil. In alkyl benzene sulfonate/alkali/methyl oleate model oil systems, methyl oleate in oil phase has two functions: on the one hand, it influences the partition of surfactant between oil and aqueous phase; on the other hand, it directly affects IFT by displacing surfactant molecule or forming mixed film with surfactant molecule at the interface.     

Clouding phenomenon and SANS studies on tetra-n-butylammonium dodecylsulfate micellar solutions in the absence and presence of salts

Clouding phenomenon in aqueous micellar solutions of an anionic surfactant tetra-n-butylammonium dodecylsulfate (TBADS) has been observed as a function of surfactant concentration. Small-angle neutron scattering (SANS) experiments in these systems show clustering of micelles as the temperature approaches the cloud point (CP). The individual micelles and the clusters of micelles coexist at CP. The clustering of micelles depends on the surfactant concentration and temperature. It is proposed that clustering is due to depletion of H-bonded water present around the butyl chains at the micellar surface. This is associated with entropy gain which is considered to be the major thermodynamic factor related to micellar aggregation. The structures (clusters) that emerge depend on the relative lengths of the alkyl chains of the counterion and can be tuned by the temperature.     

The Association of Picrate Ions with Amphiphilic Cations in Water and Aqueous Solutions of Nonionic Surfactant and β-Cyclodextrin

The interaction of cetyltrimethylammonium and cetylpyridinium bromides with picrate ions in water and aqueous solutions of the nonionic surfactant Brij 35 is studied by spectrophotometry. Spectral characteristics of the associates of picrate ions with long-chain nitrogen-containing cations depend on the concentration of a cationic surfactant. When β-cyclodextrin is added, these associates decompose owing to the formation of the strong inclusion complexes of the guest-host type with amphiphilic ions of a cationic surfactant or Brij 35 molecules. The conclusion is made that the driving force for the formation of premicellar aggregates involving picrate ions is the interactions between alkyl chains of surfactant cations. It is shown that, in the presence of various surfactants, as β-cyclodextrin concentration increases, first the molecules of nonionic surfactant and then amphiphilic cations bind with the receptor cavity. It is confirmed that there is no interaction between polyethylene glycol and β-cyclodextrin in aqueous solution.     

Synthesis of Some Oil Spill Dispersants Based on Sorbitol Esters and Their Capability to Disperse Crude Oil on Seawater to Alleviate Its Accumulation and Environmental Impact

In this respect mono‐, di‐, and tri‐ sorbitol oleate esters [SMO, SDO, and STO] were prepared and then ethoxylated using ethylene oxide to obtain six sorbitol esters at different ethylene oxide content (e.o=5, 12, 15, 20, 35, and 45). They were tested as oil spill dispersants individually and in blends. From the obtained data, it was found that the blends are more effective than the corresponding individual surfactants. The maximum dispersion capability for the prepared surfactants was obtained at HLB range from 9 to 11 for the both individual surfactants and blends. The increase of total carbon number in the surfactant alkyl group leads to increase dispersion capability of the dispersant. The wide range of ethylene oxide content was used, but the maximum dispersion efficiency was obtained at ethylene oxide=20 in E(20)STO. Meanwhile, the dispersion capability increases when the interfacial tension decreases.     

Encapsulation of non-chemically modified montmorillonite clay platelets via emulsion polymerization

This paper demonstrates that a covalent bonding between clay platelets and polymer chains is not necessary for a successful encapsulation of the inorganic compounds through emulsion polymerization. In the work described in this paper, the chemical modification of clay was performed using two kinds of titanate coupling agents: titanium IV, (2-propanolato)tris(2-propanoata-O), 2-(2-methoxyethoxy) ethanol and titanium IV, 2-propanolato,tris(isooctadecanoato-O), where the former is saturated and the second has unsaturated alkyl groups. The hydrolytic stability of the organoclays thus synthesized was thereafter investigated. It was found that the titanate modifiers were highly sensitive towards hydrolysis as evidenced by Fourier transform infrared and thermal gravimetry analyses. The effect of a chemical modification step on clay encapsulation was studied by comparing the results obtained between reactions using the synthesized organoclays and the ones using native clay platelets. It was found that the incorporation of polymerizable double bonds on clay platelets was unnecessary to achieve successful encapsulation and that, surprisingly, the chemical modification step could be omitted for the synthesis of clay-containing latex particles. The effects of monomer feed composition, i.e., monomer mixtures consisting of different weight ratios methyl methacrylate/butyl acrylate, and process types on clay encapsulation were also investigated. Both parameters were found to have a strong influence on clay encapsulation. Finally, the surfactant concentration and the surfactant type were statistically found to have a significant effect on the clay/polymer interaction as evidenced by the results of glass transition temperatures of dried latex/clay nanocomposites powders.     

A X-ray photoelectron spectroscopy study of HDTMAB distribution within organoclays

X-ray photoelectron spectroscopy (XPS) in combination with X-ray diffraction (XRD) and high-resolution thermogravimetric analysis (HRTG) has been used to investigate the surfactant distribution within the organoclays prepared at different surfactant concentrations. This study demonstrates that the surfactant distribution within the organoclays depends strongly on the surfactant loadings. In the organoclays prepared at relative low surfactant concentrations, the surfactant cations mainly locate in the clay interlayer, whereas the surfactants occupy both the clay interlayer space and the interparticle pores in the organoclays prepared at high surfactant concentrations. This is in accordance with the dramatic pore volume decrease of organoclays compared to those of starting clays. XPS survey scans show that, at low surfactant concentration (<1.0 CEC), the ion exchange between Na⁺ and HDTMA⁺ is dominant, whereas both cations and ion pairs occur in the organoclays prepared at high concentrations (>1.0 CEC). High-resolution XPS spectra show that the modification of clay with surfactants has prominent influences on the binding energies of the atoms in both clays and surfactants, and nitrogen is the most sensitive to the surfactant distribution within the organoclays.     

Sugar-based gemini surfactants with peptide bonds-synthesis, adsorption, micellization, and biodegradability

The sugar-based gemini surfactant with peptide bonds, N,N'-bisalkyl-N,N'-bis[2-(lactobionylamide)ethyl]hexanediamide (2C(n)peLac, in which n represents hydrocarbon chain lengths of 12 and 16), was synthesized by reacting adipoyl chloride with the corresponding monomeric surfactant N-alkyl-N'-lactobionylethylenediamine (C(n)peLac), which was obtained by reacting ethylenediamine with alkyl bromide and lactobionic acid. The adsorption and micellization properties of C(n)peLac and 2C(n)peLac were characterized by the measurement of their equilibrium and dynamic surface tension, steady-state fluorescence using pyrene as a probe, dynamic light scattering (DLS), and time-resolved fluorescence quenching (TRFQ), and their biodegradability was also investigated. The critical micelle concentration (cmc) decreases with an increase in the hydrocarbon chains from monomeric to gemini surfactants, whereas it increases with an increase in the chain length from 12 to 16 for both systems. The increases in both the hydrocarbon chain and the chain length of sugar-based surfactants reduce surface activities such as the ability to lower the surface tension, the occupied area per molecule, and the adsorption rate at the air/water interface. The sugar-based surfactants C(n)peLac and 2C(n)peLac exhibit unique aggregation behavior in aqueous solution. The DLS results indicate that the apparent hydrodynamic diameter of C(n)peLac micelles decreases sharply with increasing concentration, whereas that of 2C(n)peLac micelles decreases gradually. From the TRFQ measurement, it was observed that, as concentration increases, the aggregation numbers are almost constant for C(n)peLac, whereas they increase for 2C(n)peLac. These results imply that loosely packed micelles formed by sugar-based surfactants become tightly packed micelles as the concentration increases. Furthermore, it was found that 2C(n)peLac shows lower biodegradability than does C(n)peLac because it contains tertiary amines in the molecule.     

Effect of homologous series of alkyl sulfate surfactants on the emulsion polymerization of styrene. I. Equal total concentrations

There is evidence in the literature that the rates of emulsion polymerization increase by a large factor as the alkyl chain length increases for a homologous series of surfactants. However, the area occupied by a surfactant molecule in a saturated monolayer at the polystryene/water interface is independent of chain length for alkyl sulfates so that, on the basis of Gardon's theory, equal rates of polymerization would be expected when equal concentrations of surfactants are used. There is a large increase in the number of polymer latex particles formed and in the rate of emulsion polymerization as the surfactant concentration is increased through the critical micelle concentration; this accounts for the large increases reported, because the lower members of the homologous series are below their critical micelle concentrations in most of the published studies. When a common concentration is chosen that is above the critical micelle concentration even for the lowest member of the series, only a relatively small increase in latex particle number and rate of emulsion polymerization with alkyl chain length of the surfactant is observed. This is attributable to an increase in the concentration of surfactant micelles. Good agreement with Gardon's theory is obtained when the concentration of micellar surfactant is used instead of the total surfactant concentration.     

不对称Gemini表面活性剂在气/液界面的吸附动力学

合成出由1个亚甲基联接羟基和季铵基头基, 且带两根不同长度烷烃链的不对称Gemini表面活性剂CmH2m+1OCH2CH(OH)CH2N+(CH3)2C8H17Br(记为CmOhpNC8, m=10, 12, 14). 用最大泡压法研究了浓度低于临界胶团浓度时, CmOhpNC8在气/液界面上的吸附动力学. 结果表明, CmOhpNC8表现出很明显的吸附动力学效应. CmOhpNC8向新鲜气/液界面吸附时由扩散过程控制; 当界面上已具有一定吸附量时, 显示出吸附能垒Ea. 随着烷烃链的增长而明显降低, 表明长烷烃链的分子到达亚层后更容易插入表面层,这被归结为分子烷烃链间的疏水相互作用随着链增长而增强所致.