Alkyl Chain Length Of Surfactant Research Articles

Characterization of vesicles prepared with various non-ionic surfactants mixed with cholesterol

The vesicles (niosomes) prepared with hydrated mixture of various non-ionic surfactants and cholesterol were studied. The bilayer formation was characterized by X-cross formation under light polarization microscope and the ability of the vesicles to entrap water-soluble substance. Membrane rigidity was measured by means of mobility of fluorescence probe as a function of temperatures. The entrapment efficiencies of the vesicles and microviscosities of the vesicular membrane depended on alkyl chain length of non-ionic surfactants and amount of cholesterol used to prepare vesicles. The stearyl chain (C 18) non-ionic surfactant vesicles showed higher entrapment efficiency than the lauryl chain (C 12) non-ionic surfactant vesicles. Cholesterol was used to complete the hydrophobic moiety of single alkyl chain non-ionic surfactants for vesicle formation. Niosome prepared with Tween 61 bearing a long alkyl chain and a large hydrophilic moiety in the combination with cholesterol at 1:1 molar ratio was found to have the highest entrapment efficiency of water soluble substances.

A study of the effect of surfactants on the properties of polystyrene‐montmorillonite nanocomposites

AbstractPolystyrene‐Organo Montmorillonite (PS‐MMT) nanocomposites were prepared by suspension free radical polymerization of styrene in the dispersed organophilic montmorillonite. The results of X‐ray diffraction (XRD) and Transmission Electron Microscopy (TEM) indicated that exfoliated nanocomposites were achieved. The effect of organic modifiers (surfactants) on the properties of the synthesized nanocomposites was studied. It is found that polystyrene‐MMT nanocomposite with 5.0 wt% of organo‐MMT gave the greatest improvement in thermal stability, and polystyrene‐MMT nanocomposites with 7.5 wt% of organo‐MMT showed the greatest improvement in mechanical properties, compared with that of pure polystyrene (PS) in our experimental conditions. The alkyl chain length of surfactant used in fabricating organo‐MMT affects the synthesized PS nanocomposites: the longer the alkyl chain length that the surfactant possesses, the higher the glass transition temperature of the PS nanocomposite, However, the organoclay in the nanocomposites seems to play a dual role: (a) as nanofiller leading to the increase of storage modulus and (b) as plasticizer leading to the decrease of storage modulus. This results in a lower storage modulus of PS‐TMOMMT and PS‐TMTMMT nanocomposites than that of PS‐TMDMMT and PS‐TMCMMT nanocomposites. Further study is needed to confirm the above hypothesis.

Chemical and Rheological Characterization of Drag-Reducing Cationic Surfactant Systems

Surfactant drag-reducing additives are very promising for saving pumping energy in recirculation systems such as district heating and cooling systems because of their “self-repairability” after mechanical degradation compared to polymer drag-reducing additives, which degrade irreversibly. The effectiveness of cationic surfactant drag-reducing additives, as indicated by their effective drag-reduction temperatures and Reynolds number ranges, depends on the chemical structures and concentrations of the surfactants and counterions. In this paper, the effects of the surfactant (alkyl chain length, saturated/unsaturated chain, odd/even numbers of carbons, and surfactant headgroup) and counterion (size, polarity, etc.) chemical structures on surfactant drag reduction, as well as three physical properties postulated to be associated with surfactant drag reduction, are addressed. Shear-induced structure (SIS), viscoelasticity (in the forms of nonzero first normal stress difference, quick recoil, and stress oversho...

Evaluation of the factors affecting extraction of organic compounds based on the acid-induced phase cloud point approach

On the basis of a better analytical exploitation of acid-induced cloud point approach, a systematic study on the phase behaviour of acid aqueous solutions of anionic surfactants and factors affecting anionic surfactant-mediated extractions was performed. The anionic surfactants investigated were alkylsulphonates (ASS) with alkylchain lengths comprised between 8 and 16 carbon atoms. The critical hydrochloric acid concentration (minimal acid concentration required to separation in two liquid phases) was found to increase as alkylchain length of the anionic surfactant increased from 10 to 14. Non-acid-induced liquid–liquid phase separation was observed for sodium octanesulphonate (SOS) or sodium hexadecyl sulphonate (SHS) in the hydrochloric concentration range 0–10 M. Acid aqueous solutions of sodium decylsulphonate (SDeS) and sodium dodecylsulphonate (SDoS) separated into two liquid phases at temperatures ranging between 10 and 80 °C, while temperatures >35 °C were required for sodium tetradecylsulphonate. The influence on extraction efficiency and concentrating ability of experimental variables such as hydrophobicity and concentration of surfactant, nature and concentration of analyte, hydrochloric acid concentration, time and temperature of extraction and time of equilibration and centrifugation was examined. Advantages provided by anionic surfactant-mediated extractions over the use of non-ionic surfactants (cloud point extractions) are discussed.

Formation of amphiphilic complexes of cationic polyelectrolyte carrying pendant saccharide residue with anionic surfactants

The formation of amphiphilic complexes of poly(allylammonium chloride) carrying pendant maltose residue (PAAHCl-Mal) with sodium alkylsulfonates (sodium octanesulfonate (NaOcS), sodium dodecanesulfonate (NaDoS), sodium hexadecanesulfonate (NaHeDeS)) in aqueous solution was studied by means of turbidimetry, fluorescence spectroscopy using pyrene, 1H NMR and viscometry. In contrast to the complex of PAAHCl homopolymer with NaDoS, which precipitated at the ratio of the concentration of DoS to the concentration of ammonium group in the polymer, [DoS]/[NH3+]=0.01, the complexes of PAAHCl-Mal(14) containing 14mol% maltose residue with NaDoS are water-soluble over the whole range of compositions of the mixture, including the electroneutralized condition, [DoS]/[NH3+]=1. In the mixture of PAAHCl-Mal(14) and NaDoS at [DoS]/[NH3+]=1, the ratio (I3/I1) of the intensities of third and first vibrational bands of pyrene was 0.83, indicating that the complexation of PAAHCl-Mal(14) with NaDoS gives rise to a hydrophobic domain. In addition to these results, from 1H NMR and viscosity measurements of the PAAHCl-Mal(14) and NaDoS system, it seems that these species form a micelle like aggregate with a hydrophobic core from the surfactants bound to the polymer and a hydrophilic outer shell from the maltose residues. Moreover, the effects of content of maltose residue in the polymer and alkyl chain length of surfactant on the complexation of PAAHCl-Mal with alkylsulfonates are discussed.

Surface Activities of Mixtures of Partially-Quaternized 2-Vinylpyridine Telomers and Cationic Gemini Surfactant.

The surface activities of mixed surfactants of partially-quaternized 2-vinylpyridine telomers (xRn-2VPQ, x is the total number of alkyl chains, n is the alkyl chain length) and monomeric alkyltrimethylammonium bromide (1RnQ) or gemini 1, 2-bis (alkyldimethylammonio) ethane dibromide (2RnenQ) were investigated at pH 2 by surface tension, foaming property, interfacial tension and emulsification power. The mixed critical micelle concentrations (cmcs) were intermediate between the pure component xRn-2VPQ and 1RnQ or 2RnenQ. xRn-2VPQ/2RnenQ system was higher efficiencies in lowering the surface tension than xRn-2VPQ/1RnQ. The surface tension was influenced by the alkyl chain length of binary surfactants and the mole fraction (α) of xRn-2VPQ. In particular, 2.0R10-2VPQ/2R10enQ system with α = 0.50 showed the lowest surface tension. The mixtures of two cationic multialkylated surfactants improved the foaming properties as compared with the pure component cationic surfactants. The similar trends in the surface tension and the foaming properties were observed for the lowering abilities of the interfacial tension at the water / toluene interface and emulsion stabilities.

Fiber-like Gold Particles Prepared in Cationic Micelles by UV Irradiation: Effect of Alkyl Chain Length of Cationic Surfactant on Particle Size

Fiber-like gold particles were prepared by irradiation of HAuCl4 solutions at 253.7 nm in the presence of alkyltrimethylammonium chlorides (CnTAC: n=10, 12, 14, and 16). Fiber-like gold particles were obtained above a threshold concentration of CnTAC. The length of fiber-like gold particles increases with increasing alkyl chain length of CnTAC.

Immobilized enzymes in ordered mesoporous silica materials and improvement of their stability and catalytic activity in an organic solvent

Enzyme immobilization in mesoporous materials with various pore sizes was studied. The size of the mesopores was controlled by means of the combination of the alkyl chain lengths of surfactants and a swelling agent (triisopropyl benzene). Enzymes were selectively adsorbed to FSM-16 and MCM-41 prepared with a cationic surfactant, whose pore sizes were over the molecular diameters of the enzymes, and were not adsorbed significantly to SBA-15 prepared with a non-ionic surfactant. The higher adsorption as to FSM-16 or MCM-41 rather than on SBA-15 may be due to the ionic characteristics of the mesopore, which would be consistent with the observed larger adsorption capacity as to the cationic pigment rather than the anionic pigment of these materials. Enzymes, horseradish peroxidase and subtilisin, immobilized in FSM-16 showed the best stability and peak catalytic activity in an organic solvent when the average mesopore size just exceeded the molecular diameters of the enzymes.

DNA Phase Behavior in the Presence of Oppositely Charged Surfactants

The interaction between DNA and alkyltrimethylammonium bromides of various chain lengths has been investigated. It is known that these systems phase separate with the formation of a precipitate; this important feature allows, for example, purification of nucleic acids. Phase maps were drawn for the aqueous systems illustrating the associative phase separation. The boundary of the two-phase region for the dilute part of the phase diagram was evaluated by turbidimetry, in both the absence and presence of salt. The extension of the precipitate region increases strongly with the surfactant alkyl chain length, and we observed no redissolution with an excess of surfactant. The addition of NaBr led to novel interesting findings. The phase diagram studies were correlated with the single molecule conformational behavior of the same systems as studied for very diluted solutions by fluorescence microscopy. DNA exhibits a discrete phase transition in the presence of cationic surfactants from coils to globules. Result...

Characterization of MCM-48 Silicas with Tailored Pore Sizes Synthesized via a Highly Efficient Procedure

MCM-48 silicas have been prepared via a high-yield synthesis procedure using mixtures of cationic alkyltrimethylammonium surfactants (alkyl chain length from 12 to 20 carbon atoms) and neutral cosurfactants. This is the first reported successful synthesis of MCM-48 using eicosyltrimethylammonium surfactant. The samples, especially those synthesized using cationic surfactants with cetyl, octyl, and eicosyl chains, were found to exhibit a high degree of structural ordering, which manifested itself in very well-resolved X-ray diffraction (XRD) patterns, and remarkably narrow capillary condensation steps after the template removal. The latter could be achieved not only via calcination, but also via ethanol/HCl washing. The unit-cell size and pore size of MCM-48 were found to be determined by the alkyl chain length of the cationic surfactant used. The calcined MCM-48 samples had BET specific surface areas of about 1100 m2 g-1, large primary mesopore volumes (up to 1.15 cm3 g-1), XRD d211 interplanar spacings f...

Effects of a homologous series of linear alcohol ethoxylate surfactants on fathead minnow early life stages.

Effects of a homologous series of three primarily linear alcohol ethoxylate surfactants were studied in laboratory flow-through 28-day early-life-stage tests with fathead minnow (Pimephales promelas Rafinesque). Surfactants were a C(9-11), C(12-13), and C(14-15) with an average of 6, 6.5, and 7 ethylene oxide units per mole of alcohol, respectively. Average measured surfactant recoveries were 103%, 81%, and 79% of nominal concentrations for the C(9-11) EO 6, C(12-13) EO 6.5, and C(14-15) EO 7 studies, respectively. Embryo survival at 48 h was not adversely affected at any of the concentrations tested. Impaired hatching and deformed fry were observed only in the C(12-13) EO 6.5 study. The 28-day LC50 values were 4.87, 2.39, and 1.02 mg/L for the C(9-11) EO 6, C(12-13) EO 6.5, and C(14-15) EO 7 surfactants, respectively. The corresponding NOECs for survival were 1.01, 1.76, and 0.74 mg/L. Posthatch fry growth was more sensitive than survival for the C(12-13) EO 6.5 and C(14-15) EO 7 surfactants. Survival of posthatch fry decreased with increasing surfactant alkyl chain length. Twenty-eight-day laboratory data were compared to 96-h laboratory, 10-day laboratory and 30-day stream mesocosm data for fathead minnow previously determined for these surfactants. Survival endpoints from the different exposures were comparable and only varied within a factor of two. Similarity of results suggests that it is possible to effectively use 96-h, 10-day, or 28-day laboratory data to predict environmental effects concentrations of these surfactants for fish. http://link.springer-ny. com/link/service/journals/00244/bibs/37n4p536.html</++ +HEA

Structure and Molecular Fluctuations of n-Alkyl-β-d-glucopyranoside Micelles Determined by X-ray and Neutron Scattering

The structure of micelles of n-alkyl-β-d-glucopyranosides in aqueous solution have been determined as a function of alkyl chain length and isotopic composition of the solvent, using a combination of X-ray and neutron scattering techniques. The combined use of X-ray and neutron scattering over an extended q-range has led to an enhanced resolution of micelle structure. Numerical modeling of both X-ray and neutron scattering data found that n-alkyl-β-d-glucopyranoside micelle shape could be best fit with a cylindrical core−shell form factor, with dimensions dependent upon the surfactant concentration and alkyl chain length. While the micelle core diameter was found to increase proportionately with changes in the alkyl chain length, significantly larger changes were found for the micelle length. The drastic increases in micelle length with increasing surfactant chain length is interpreted to reflect imperfect packing of the surfactant in the cap regions and solvent exposure of the alkyl chains. X-ray scatteri...

Formation and Transition of Highly Ordered Structures of Polyelectrolyte−Surfactant Complexes

Small-angle X-ray scattering studies on the nanostructures of water-equilibrated complexes, formed by slightly cross-linked copolymer gels of poly(sodium methacrylate/N-isopropylacrylamide) P(MAA/NIPAM) and fully charged sodium polystyrenesulfonate (PSS), respectively, interacting with oppositely charged surfactants of alkyltrimethylammonium bromide (CnTAB, with n being the number of carbon atoms in the alkyl chain) at ∼23 °C, are presented. In P(MAA/NIPAM)−CnTA complexes, the formation and transition of highly ordered structures were investigated in terms of the surfactant alkyl chain length and the hydrophobicity of the polyelectrolyte chain. The complexes between fully charged PMAA gel and CnTAB showed Pm3n cubic structures at 10 ≤ n ≤ 16 but did not show highly ordered structures at n = 8 and 18 due to the weak hydrophobic interaction and the steric hindrance of the long alkyl chains inside the gel, respectively. In complexes formed by moderately charged P(MAA/NIPAM) gel with CnTAB, the decrease in th...

Solubilization of model stratum corneum liposomes by quaternary ammonium surfactants

AbstractThe solubilizing interactions of a series of quaternary ammonium surfactants [alkyl chain lengths C‐12 (DoTAB), C‐14 (TeTAB), and C‐16 (HeTAB)] with liposomes formed by a mixture of lipids modeling the stratum corneum (SC) lipid composition (40% ceramides, 25% cholesterol, 25% palmitic acid, and 10% of cholesteryl sulfate) were investigated. Surfactant/lipid molar ratios (Re) and bilayer/aqueous phase partition coefficients (K) were determined by monitoring changes in static light scattering of the system during solubilization. Free surfactant concentration was always similar to the critical micelle concentration (CMC). A general assumption for phosphatidylcholine (PC) liposomes suggests that the free surfactant concentration must reach CMC for solubilization to occur. This assumption can be applied to SC liposomes in this study, and indicates that liposome solubilization was mainly driven by mixed micelle formation. The Re and K parameters fell as the surfactant alkyl chain length decreased or CMC increased. Thus, a higher CMC corrsponds to an increased ability of these surfactants to saturate or solubilize SC liposomes and to a lower degree of partitioning into liposomes or affinity with these bilayer structures. The overall balance of these opposing tendencies shows that TeTAB had the highest effectiveness with respect to the saturation and solubilization of SC structures in terms of total surfactant needed to produce these effects. Different trends in surfactant interaction with SC liposomes were observed when comparing Re and K parameters with those for PC liposomes. Because SC liposomes were more resistant to the surfactant action, the affinity of surfactants with these bilayer structures was higher in all cases.

Bulk and Surface Behavior of Cationic Guars in Solutions of Oppositely Charged Surfactants

We study the bulk and surface behavior of aqueous mixtures of cationic guars and anionic sulfate surfactants. The phase diagrams are determined and the phases characterized with a variety of techniques. When the surfactant is gradually added, the polyelectrolyte is physically modified by ionic binding of the surfactant or more likely surfactant aggregates to the polymer chains. This results in the increase of the solution viscosity and leads to phase separation between a polymer- and surfactant-rich phase and a dilute supernatant. Phase separation always occurs for surfactant concentrations below the critical micelle concentration (cmc). A second one-phase region is obtained for surfactant concentration as low as twice the cmc, independent of the polymer charge density or of the alkyl chain length of the sulfate surfactant. The surface behavior is investigated with a surface forces apparatus. The force profiles between two layers of cationic guar preadsorbed onto mica surfaces are measured in water and in surfactant solutions for concentrations covering the three regions of the bulk-phase diagram. We conclude that the structure of the adsorbed layers is clearly related to the structure of the corresponding polymer/surfactant mixtures.

Staging of Organic and Inorganic Gallery Cations in Layered Silicate Heterostructures

Heterostructured fluorohectorite clays with regularly alternating interlayers of inorganic and organic exchange cations have been prepared through ion exchange reaction of the sodium clay in aqueous suspension with half an equivalent of alkylammonium ions. In order to elucidate this staging-like behavior of the intercalates, the exchange process was examined for a series of onium ion surfactants of the type [CnH(2n+1)N(CmH(2m+1))3]+. One set of onium ions varied the alkyl chain length (n=4–22), while maintaining a constant onium head group size (m=4). A second set varied the head group size (m=1–5), while the chain length remained fixed (n=16). Two fundamental factors, namely, alkyl chain length and head group size determined staging behavior. The surfactant alkyl chain length determined the extent of Na+replacement by onium ions. Relatively little Na+exchange (∼10%) occurred for the short chain onium ions withn=4,m=4 andn=6,m=4. The replacement of Na+by onium ions became more favorable as the alkyl chain length was increased ton=8 or 10. For very hydrophobic surfactants withn≥12, onium ion uptake was essentially quantitative, affording 1:1 mixed Na+–onium ion intercalates. The “footprint” or area covered by the onium ion head group on the interlayer surface controlled heterostructure formation for the 1:1 intercalates. Form≥3 the head group footprint matched the clay surface charge density and precluded the mixing of organic and inorganic exchange cations within the same gallery. The segregation of the hydrophobic organic cations and the hydrophilic inorganic cations on the internal and external surfaces of two-nanolayer tactoids during the ion exchange process was proposed as the pathway for staging behavior in the heterostructured intercalates. The smaller footprints of trimethyl and triethyl onium ion head groups (m=1,2) allowed for comingling of the exchange ions on single-nanolayer tactoids and the formation of phase–segregated organic and sodium ion clays upon stacking of the tactoids.

Solubilization of phosphatidylcholine unilamellar liposomes caused by alkyl glucosides

AbstractSolubilizing alterations caused by a series of alkyl glucosides (alkyl chain lengths ranging from C8 to C12) in phosphatidylcholine (PC) unilamellar liposomes were investigated. Surfactant‐to‐phospholipid molar ratios (Re) and bilayer/aqueous phase partition coefficients (K) were determined by monitoring changes in static light scattering (SLS) of the system during solubilization. At the two interaction levels investigated (surfactant concentrations producing SLS values of 100 and 0% for each surfactant/PC system studied) the free surfactant concentration for each surfactant was always comparable to its critical micelle concentration (CMC). This indicates that liposome solubilization was mainly ruled by mixed micelle formation. A rise in CMC (or decrease in the surfactant alkyl chain length) resulted in an increase in the ability of these surfactants to saturate or solubilize PC liposomes and, inversely, in an abrupt decrease in their affinity with these bilayer structures. The overall balance of these opposite tendencies shows that the octyl glucoside had the highest ability to saturate and solubilize liposomes (lowest Re values), whereas the dodecyl glucoside exhibited the highest degree of partitioning into liposomes or affinity with bilayer structures (highest K values). From a practical viewpoint, the use of nonyl glucoside reduced approximately 2.5 times the concentration needed to saturate and solubilize 1.0 mM PC liposomes with respect to that needed using the conventional octyl glucoside.

Spectroscopic Studies of the Interaction of Methyl Orange with Cationic Alkyltrimethylammonium Bromide Surfactants

The spectral signature of the azo dye methyl orange (MO) exhibits a considerable sensitivity to the polarity of the dye's environment. We have used this dependence of absorption wavelength on microenvironment to investigate the 1:1 ion pair complexes formed from electrostatic interaction of a series of cationic alkyltrimethylammonium bromide (CnTAB) detergents with the anionic organic probe in aqueous solution. At surfactant concentrations far below the critical micelle concentration, MO shifts in absorbance λmaxfrom 462 nm in aqueous solution to 367–377 nm upon complex formation. Nonlinear least-squares deconvolution of the absorbance spectra reveals a previously unreported significant blue shift in λmaxwith increasing surfactant alkyl chain length. Our time-dependent spectrophotometric studies of the MO–CnTAB complex systems reveal, also for the first time, that a subsequent spectral shift to shorter wavelengths (λmax= 348–350 nm) occurs for those alkyl chain lengths greater thann= 14. These observations are consistent with an aggregation of the surfactant–dye pair after initial complex formation. Increased hydrophobic interaction of the azo ring of the probe with additional neighboring surfactant alkyl chains to achieve a final equilibrium state is hypothesized to account for the MO absorbance spectral shift.

Interaction of Cationic Surfactants with Iron and Sodium Montmorillonite Suspensions

Calorimetry, static technique, and X-ray diffraction (XRD) analysis were employed to study the adsorption of cetyltrimethylammonium bromide (CTAB) and dodecyltrimethylammonium bromide (DTAB) on Fe–montmorillonite and Na–montmorillonite suspensions. The results show that the process of adsorption is exothermic and that the type of clay and the alkyl chain length of surfactant affect the amount of adsorption and the enthalpy of adsorption significantly but that the effect of temperature is very limited in the temperature range studied. The magnitudes of adsorption amount and adsorption enthalpy follow the order Na-montmorillonite > Fe-montmorillonite, CTAB > DTAB. The basal spacings determined by X-ray powder diffraction indicate that the CTAB adsorbed between the clay interlayers in a bilayer arrangement, while the DTAB formed bilayers or monolayers at saturation adsorption between the Na-montmorillonite and Fe-montmorillonite interlayers, respectively. The adsorption mechanism is also discussed on the basis of the experimental data.

Preparation of Organic Particles by Complexation between Cationic and Anionic Surfactants in Aqueous Solution

The complexation between cationic and anionic surfactant was monitored by changing molecular ratio between cationic and anionic surfactant molecule and alkyl chain length of anionic surfactant. The precipitation was identified with elemental analysis, SEM and UV-vis spectrophotometer. The relative degree of precipitation was determined by weighing the amount of precipitation and the size of the precipitation was determined with light scattering. This study enabled the preparation of organic charge transfer complex by ionic surfactants.