Addition Of Surfactant Sodium Dodecyl Sulfate Research Articles

Influence of hydroxypropylmethyl cellulose–sodium dodecylsulfate interaction on the solution conductivity and viscosity and emulsion stability

The conductivity, viscosity and rheological measurements were used to study the interaction of HPMC with an anionic surfactant-sodium dodecylsulfate (SDS) in aqueous solutions of different concentrations. The properties of HPMC solutions (0.1–1.0%) with increasing SDS concentrations (0–2.0%) were investigated. On the basis of following the changes of the system during the HPMC–SDS interaction, the characteristic concentrations of SDS at which interaction starts (the critical aggregation concentration (CAC)) and at which it ends (polymer saturation point (PSP)), were determined, and an interaction mechanism was proposed. The linear relationship between the PSP and HPMC concentrations was found, while CAC remained constant. To show that the interaction of the components in the continuous phase of dispersed systems can change their properties, the changes of stability of HPMC-stabilized oil-in-water emulsions with SDS addition were also examined. It was found that stability of the emulsions was influenced by the HPMC–SDS interaction. After the preparation, stability of emulsions increased with increase in continuous phase viscosity and stability changed with time according to the mechanism of HPMC–SDS interaction in the continuous phase.

Aggregation behavior of acrylamide/2-phenoxyethyl acrylate and its interaction with sodium dodecyl sulfate in aqueous solution studied by proton 1D and 2D NMR

H-1 NMR self-diffusion coefficient, spin-lattice relaxation time, spin-spin relaxation time, and two-dimensional nuclear Overhauser enhancement (2D NOESY) measurements have been used to study the association behavior of a novel hydrophobically associating copolymer composed of acrylamide ( AM) and a small amount of 2-phenoxyethyl acrylate ( POEA), and its interaction with the anionic surfactant sodium dodecyl sulfate (SDS). Three sets of copolymers with approximately the same composition but with different hydrophobic POEA contents were investigated. The POEA contents for these copolymers were about 1.41, 1.03, and 0.56 mol% respectively, as validated by H-1 NMR spectra. Self-diffusion coefficient measurements show that the aggregation process occurs in a relative narrow concentration range and the critical association concentrations (cacs), of these copolymers are within this narrow concentration range, which are in agreement with those measured by viscosity measurements (6 g L-1). Above this concentration, the hydrophobic POEA moieties are found to associate and possibly build a transitory three-dimensional network along the polyacrylamide (PAM) backbones, which induces a strong decrease in NMR parameters including self-diffusion coefficients and relaxation times. The surfactant SDS showed a significant interaction with the copolymer in the dilute solution. Addition of SDS resulted in the binding of SDS on copolymer POEA-PAM segments and reinforced the interchain transient network formation of copolymer at a concentration below its cac. In the SDS/POEA-PAM mixed systems, the hydrophobic methylene groups of the SDS molecules were preferentially located in the vicinity of the phenoxy groups of the POEA hydrophobes.

Ternary Conjugates as a Result of Exchange Reactions Between Polyelectrolyte Complexes and Surfactants: Formation and Stability

AbstractSummary: The exchange of sodium polymethacrylate (Na‐PMA) for anionic surfactant sodium dodecylsulfate (SDS) in a polyelectrolyte complex of Na‐PMA and poly(L‐lysine) (PLL) was studied by light scattering techniques. The exchange reaction proceeds inside the complex particles without any aggregation. It causes swelling of the particles and the formation of thick polymer shell around them. In order to prove the formation of the shell, the colloidal stability of the particles in salt solutions was studied. The addition of SDS to a complex solution dramatically increases colloid stability. The stability was found to be independent of the mixing ratio of the initial complex, depending only on the molecular weight of Na‐PMA and slowly decreasing with time. The mechanism of the exchange reaction was proposed. The addition of SDS causes fast substitution of charged units of Na‐PMA for surfactant molecules in the complex and formation of the PLL/SDS complex stabilized by hydrophobic interactions between aliphatic chains of SDS. The Na‐PMA chains cannot be released sufficiently fast from the particles due to entanglements of the chains inside the particles. They build a thick stabilizing shell around the particles and lead to their swelling. This shell protects the particles against coagulation at relatively high salt concentrations. However, such state of the particles does not correspond to thermodynamic equilibrium. Na‐PMA is very slowly released from the particles, decreasing the density of stabilizing shell and stability of the particles in salt solutions. The possible application of ternary conjugates in drug delivery is discussed.Schematic representation of changes in structure and stability of Na‐PMA/PLL complex particles upon the exchange of polyanion Na‐PMA for negatively charged surfactant SDS.magnified imageSchematic representation of changes in structure and stability of Na‐PMA/PLL complex particles upon the exchange of polyanion Na‐PMA for negatively charged surfactant SDS.

Study on the interaction of anionic dye–nonionic surfactants in a mixture of anionic and nonionic surfactants by absorption spectroscopy

The interaction between an anionic dye C.I. Reactive Orange 16 (RO16) and different surfactants, i.e., the anionic surfactant sodium dodecylsulfate (SDS) and nonionic surfactants polyoxyethylene ethers (C m POE n ; m = 12, 16 and 18, n = 4, 10 and 23) has been researched spectrophotometrically in a certain micellar concentration range. Light absorbances in the visible spectral range are measured as a function of mole fraction of surfactant at four different temperatures and at 24 h over the periodic time intervals. For this reason, a typical system occurred at 1.0 × 10 −2 mol/l for surfactants and at 1.0 × 10 −4 mol/l for dye concentrations. It is evident from the experimental measurements that while nonionic surfactants form a complex with the anionic dye RO16 in aqueous solution in studied concentration range, anionic surfactant does not. The formation of C m POE n –RO16 complex in the SDS solutions of different mole fractions in its micellar concentration range has been determined and compared to those obtained in the dye–surfactant binary mixtures. Spectrophotometric measurements indicated that the value of absorbance of SDS–RO16 is greater than that of nonionic surfactant–RO16 in the binary systems. This state explains that the ionic and hydrophobic interactions between SDS–RO16 are less than that of nonionic surfactant–RO16 interactions. The addition of SDS to the mixture of C m POE n –RO16 causes an increase in the value of absorbance. This increase is due to changed hydrophobic–hydrophilic balance of the studied mixtures. Furthermore, we observed that the alkyl chain length and the number of polyoxyethylene in nonionic surfactants do not have an enormous effect on the values of absorbance.

Temperature Quenched DODAB Dispersions: Fluid and Solid State Coexistence and Complex Formation with Oppositely Charged Surfactant

Dilute dispersions of the synthetic bilayer forming double-chained cationic lipid dioctadecyldimethylammonium bromide (DODAB) were investigated. In dispersions sonicated above the chain melting temperature Tm (approximately 45 degrees C) it was found by H NMR that about 50% of the surfactant chains remained fluid when the samples were cooled to room temperature, which is 20 degrees C below Tm. In contrast, there was no sign of a fluid fraction in unsonicated samples at room temperature. The addition of the anionic surfactant sodium dodecyl sulfate (SDS) to DODAB dispersions at room temperature resulted in the formation of an essentially stoichiometric DODA-DS complex with frozen chains, as seen by titration calorimetry and H NMR experiments. For sonicated samples, turbidity experiments demonstrated that, after a fast complexation reaction, the system remains colloidally stable unless the SDS-to-DODAB mixing ratio is too close to unity. H NMR experiments also showed that in the unreacted DODAB the fraction of fluid chains remained close to 50%, indicating either that SDS reacts equally fast with fluid and frozen DODAB or that there is a relaxation of the fluid fraction after the complexation. The melting enthalpy and the melting temperature of the alkyl chains rise gradually as the mixing ratio increases. We observed with cryo-TEM that the fraction of large unilamellar vesicles was significantly larger after addition of SDS. This indicates vesicle fusion. Based on both wide- and small-angle X-ray scattering patterns, the structure of the equimolar SDS-DODAB complex at 25 degress C was proposed to be lamellar.

Mixed cationic/anionic surfactants for semipermanent wall coatings in capillary electrophoresis.

Mixtures of the cationic surfactant cetyltrimethylammonium bromide (CTAB) with the anionic surfactant sodium dodecyl sulfate (SDS) form more stable coatings in fused-silica capillaries than CTAB alone. The reversed electroosmotic flow (EOF) generated by CTAB/SDS mixtures remains stable for over 80 min after removal of the surfactants from the buffer. Enhanced stability (relative to CTAB alone) was found even when the ratio of SDS to CTAB was as low as 1%. This greater coating stability is attributed to the structural transition from adsorbed micelle to bilayer, which is induced by addition of SDS. Separation of a mixture of basic proteins yielded efficiencies of 364 000-562 000 plates/m and recoveries ranging from 85% to 98%. Migration time reproducibility was less than 0.9% relative standard deviation (RSD) from run to run and less than 2.6% RSD from day to day.

Use of sodium dodecyl sulfate as an antifouling and homogenizing agent in the direct determination of heavy metals by anodic stripping voltammetry.

The effectiveness of the anionic surfactant sodium dodecyl sulfate (SDS) for suppressing adsorption interferences in anodic stripping voltammetry (ASV) was investigated. The samples included fruit juices, wine, beer, milk powder and waste water, and the analytes were cadmium, lead and copper. In most of the samples, the ASV signals were severely depressed or even absent due to electrode fouling, but addition of SDS in concentrations up to 10 g L(-1) proved effective in restoring the ASV response. By using SDS as an interference suppressor, the content of lead and copper in a milk powder reference material was determined, and the results were in agreement with the certified values. In this determination, which could not have been performed without SDS, the surfactant also served as a homogenizing agent, preventing separation of the sample components. The effect of SDS was explained by the interaction of the surfactant with the electrode surface and with the constituents of the sample matrix.

Parameters Affecting the Lower Critical Solution Temperature of Linear and Crosslinked Poly(N‐ethylacrylamide) in Aqueous Media

AbstractA series of linear poly(N‐ethylacrylamide) (PEA) samples varying in molar mass has been prepared by free radical polymerization in the absence and presence of a chain transfer agent and a hydrogel of PEA has been prepared using N,N‐methylenebisacrylamide (BIS) as crosslinker. The lower critical solution temperatures (LCST) of the linear polymers in water and aqueous media were determined turbidimetrically as a function of molecular weight, concentration, heating/cooling rate, and concentrations of KCl and anionic surfactant sodium dodecyl sulfate (SDS) in the aqueous solution. The corresponding LCST for the hydrogel was determined from the gravimetric swelling ratios (r). In pure water the values of LCST for linear polymer and hydrogel are 73 °C and 62 °C, respectively. The LCST of linear PEA increases with decreasing molecular weight. The swelling ratio for gels and the LCST for solutions and gels increased with the inclusion of SDS into water. The opposite effects prevailed on inclusion of KCl into water or incorporation of crosslinker. Additionally, the rates of heating/cooling play a significant role in the measured value of LCST. Hence the swelling ratio of hydrogel or the LCST can be adjusted via 1) addition of either SDS or KCl into water; 2) use of different molecular weight samples; 3) incorporation of crosslinker into polymer chain. magnified image

Direct Force Measurements between α-Alumina Surfaces with Adsorption of Anionic Surfactant/Polymer Mixtures

Direct measurements of interaction forces between α-alumina surfaces with coadsorbed anionic surfactant sodium dodecyl sulfate (SDS) and anionic polyelectrolyte poly(sodium 4-styrenesulfonate) (PSS) at pH 3.5 are carried out by colloidal probe atomic force microscopy. It is found that in aqueous PSS solutions the interaction forces are dependent on the initial PSS concentration. At low PSS concentration the electrostatic repulsion initially present is neutralized, resulting in a weak attraction between the surfaces, while as the concentration is increased further, repulsive forces reappear due to the additional adsorption of PSS on the surface. The adsorbed PSS adopts a relatively flat conformation at all PSS concentrations investigated. On the other hand, the interaction forces are dramatically different for the simultaneous addition of SDS and PSS: the force profile for the coaddition comes progressively close to that for the addition of SDS alone with increasing SDS concentration. This is attributed to the fact that SDS plays a key role for the coadsorption of SDS and PSS over a high SDS concentration region. The dispersion stability and ζ potential of α-alumina suspensions are evaluated for comparison with the resultant forces, and a good correlation is obtained between them. The effects of sequential addition of SDS and PSS are also investigated.

Thermoreversible swelling behaviour of hydrogels based on N-isopropylacrylamide with a hydrophobic comonomer

Hydrogels were prepared by free radical polymerisation in aqueous solution of N-isopropylacrylamide (NIPA) and of NIPA with di- n-propylacrylamide (DPAM), di- n-octylacrylamide (DOAM) or di-dodecylacrylamide (DDAM) as hydrophobic comonomer. N, N-methylene bisacrylamide (BIS) and glyoxal bis(diallyacetal) (GLY) were used as crosslinkers. A series of copolymers with three different comonomer contents was synthesised and for some polymers three different crosslinker concentrations were employed. The swelling equilibrium of these hydrogels was studied as a function of temperature, hydrophobic comonomer species and content in aqueous solutions of the anionic surfactant sodium dodecyl sulfate (SDS). In pure water the gels showed a discontinuous volume phase transition at 33 and 30 °C for PNIPA and hydrophobically modified PNIPA copolymeric hydrogels, respectively. The swelling ratio r and the transition temperature (LCST) increased at low temperatures with the addition of SDS, this is ascribed to the conversion of non-ionic PNIPA gels into polyelectrolyte gels through the binding of SDS. At SDS concentration below 0.5 wt%, gels exhibited a single discontinuous volume transition at 36–38 °C. However, for SDS concentration above 0.5 wt%, two discontinuous volume transitions at 36–40 and 70 °C were observed. Additionally, the replacement of BIS by the novel octafunctional crosslinker glyoxal bis(diallylacetal) (GLY) yielded an increase in the swelling ratio.

Microstructures formed in aqueous solutions of a hydrophobically modified nonionic cellulose derivative and sodium dodecyl sulfate: a fluorescence probe investigation

The association behavior of hydrophobically modified ethyl hydroxyethyl cellulose (HM-EHEC) and its interaction with the anionic surfactant sodium dodecyl sulfate (SDS) has been studied in the dilute concentration regime. Steady-state fluorescence probe techniques have been utilized to obtain microstructural information of the system properties and combined with macroscopic bulk information from equilibrium dialysis experiments in order to determine binding isotherms of SDS to HM-EHEC. HM-EHEC was found to self-associate and form polymeric micelles in semi-dilute aqueous solutions. c ∗ for the self-association process was determined to be approximately 0.4%. The microviscosity of the polymeric micelles is much higher, and the micropolarity slightly higher, than that of ordinary SDS micelles. The onset of interaction between HM-EHEC and SDS was evidenced by a simultaneous strong increase in microviscosity and decrease in micropolarity upon successive addition of SDS. There is a minor, noncooperative SDS binding to the HM-EHEC starting from low concentrations of SDS (<5 mM) followed by a highly cooperative binding region at SDS concentrations ≥5 mM. The polymer–surfactant aggregates are rigid and hydrophobic with a maximum in microviscosity in the noncooperative binding region at a very low degree of SDS-adsorption.

Interactions between polyampholytes and ionic surfactants

The interactions of two partially charged ampholytic terpolymers [consisting of acrylamide, sodium 2-acrylamido-2-methylpropanesulphonate, and 2-(methacryloyloxyethyl)trimethylammonium chloride segments with molar compositions 80/12/08 and 80/08/12] and two fully charged ampholytic copolymers (containing only the two latter comonomers with molar compositions of 80/20 and 50/50), with cationic surfactants [tetradecyl- trimethylammonium bromide (TTAB) and cetyltrimethylammonium bromide (CTAB)] and the anionic surfactant sodium dodecylsulphate (SDS), are investigated. The studies include phase behaviour (swelling, solubilisation, precipitation), viscometry, electrical conductivity, and potentiometry (bromide ion and surfactant ion-specific electrodes). The 80/08/12 and 80/12/08 polyampholytes swell in water and are solubilised in the presence of cationic or anionic surfactants above a particular surfactant concentration that is proportional to the polymer concentration. The polyampolyte 80/20 is soluble in water but precipitates in the presence of TTAB, whereas 50/50 is insoluble in water and in the presence of TTAB, but is solubilised upon addition of SDS. The results indicate that TTAB binds to 80/12/08 with little or no cooperativity. Solubilisation appears to be the result of the increasing polyelectrolyte character of the polyampholyte upon neutralisation of its charged sites by bound surfactant ions of opposite charge. The binding of TTAB by the 50/50 polyampholyte is very weak and non-cooperative. In contrast, 80/20 binds TTAB cooperatively, much like a true polyelectrolyte-surfactant system of opposing charges. In particular, the binding is characterised by the existence of a critical aggregation concentration. A partial phase diagram for this system has been determined from the TTA+-electrode potential data. The behaviour of true polyelectrolytes and polyampholytes, with respect to their interaction with surfactants, is discussed.

The effect of sodium dodecylsulfate on gelatinization and gelation properties of wheat and potato starches

The surfactant sodium dodecylsulfate (SDS) has previously been reported to have an influence on the gelatinization and gel forming properties of different starches. In the present study, the effects of SDS were primarily studied by brightfield microscopy and discussed in relation to data obtained by differential scanning calorimetric (DSC) and dynamic rheological measurements on wheat and potato starches. By DSC measurements, it was confirmed that addition of SDS will cause a reduction in the enthalpies of the main endothermic transition and will shift the onset temperatures downwards. Addition of the surfactant will also cause an increase in the enthalpy of the endotherm belonging to the amylose-lipid complex, indicating the formation of an amylose-SDS complex. The micrographs indicated that the staining properties of mainly the amylose fraction was changed in presence of the surfactant. It was also observed that a stepwise increase of the concentration of SDS in starch solutions, heated at constant tem- peratures, caused swelling, folding, and finally collapse of the granules, indicating an earlier gelatinization. Rheological data, in combination with exothermic DSC-data, showed that the amylose-SDS complex had a profound influence on the elastic properties of the gels

The Effect of Sodium Dodecyl Sulfate and M-α-Cyclodextrin on the Solubility and Partitioning of Xylenes in Aqueous Solutions

The solubility and the partitioning ofp- ando-xylene in aqueous solutions containing M-α-CD, a partially methylated α-cyclodextrin, and the anionic surfactant sodium dodecyl sulfate (SDS) were studied by extraction experiments to evaluate the applicability of liquid membrane permeation for the separation of xylene isomeres. Experiments were carried out with the pure xylenes and 1:1 mixtures ofo- andp-xylene. The interactions of M-α-CD and SDS and their effects on the solubility and partitioning of xylenes were investigated. M-α-CD was found to form 1:1 complexes withp- ando-xylene. Formation constants were determined as 141M−1forp-xylene and 48M−1foro-xylene, respectively, which are higher than those reported with nonmethylated α-CD. This can be explained by additional hydrophobic interactions with the methyl groups of the cyclodextrin. In contrast to the solubility in CD solutions,o-xylene was found to be more soluble thanp-xylene in aqueous solutions of SDS. At constant concentrations of M-α-CD the addition of SDS led to the displacement ofp-xylene from the cyclodextrin cavity, which resulted in a decrease in its solubility. This decrease lasted until micelles were formed. Due to the solubilization ofp-xylene in the micelles, further addition of SDS resulted in a linear increase in the solubility ofp-xylene. However, at constant CD concentrations the solubility ofo-xylene increased with the addition of SDS until about 5 mmol/liter SDS. This might be attributed to the formation of a ternary complex consisting of cyclodextrin,o-xylene, and SDS. At SDS concentrations greater than 5 mmol/liter, the solubility ofo-xylene decreased, which was probably due to the formation of a more stable complex between SDS and M-α-CD. An addition of SDS beyond a critical concentration (CMC), where micelles are formed, resulted again in a linear increase ofo-xylene solubility. The CMC was found to depend linearly on the concentration of M-α-CD in aqueous solution. Extraction experiments with a 1:1 mixture ofo- andp-xylene showed that the two xylenes and SDS are in competition for M-α-CD. Since surfactants are always present when using emulsion liquid membranes and due to the complex interactions between SDS, the xylenes, and M-α-CD, no sufficient selectivity for the separation of the xylenes by liquid membrane permeation could be achieved.

SDS-degrading bacteria attach to riverine sediment in response to the surfactant or its primary biodegradation product dodecan-1-ol

A laboratory-scale river microcosm was used to investigate the effect of the anionic surfactant sodium dodecyl sulphate (SDS) on the attachment of five Pseudomonas strains to natural river-sediment surfaces. Three of the Pseudomonas strains were chosen for their known ability to express alkylsulphatase enzymes capable of hydrolysing SDS, and the other two for their lack of such enzymes. One strain from each category was isolated from the indigenous bacterial population present in the river sediment used; other isolates were from soil or sewage. The alkylsulphatase phenotypes were confirmed by gel zymography of cell extracts. Addition of SDS to mixed suspensions of river sediment with any one of the biodegradation-competent strains stimulated the attachment of bacteria to the sediment particles. In contrast, the attachment of biodegradation-incompetent strains was weak and, moreover, was unaffected by SDS. The SDS-stimulated attachment for competent organisms coincided with rapid biodegradation of the surfactant. The primary intermediate of SDS biodegradation, dodecan-1-ol, accumulated transiently, and the numbers of attached bacteria correlated closely with the amount of dodecan-1-ol present. Direct addition of dodecan-1-ol also stimulated attachment but the effect was more immediate compared with SDS, when there was a lag period of approximately 2 h. To account for these observations, a model is proposed in which SDS stimulates the attachment of biodegradation-competent bacteria through its conversion to dodecan-1-ol, and it is hypothesized that the observed reversibility of the attachment is due to the subsequent removal of dodecan-1-ol by further bacterial metabolism.

Structure of solid dispersions in the system polyethylene glycol-griseofulvin with additions of sodium dodecyl sulphate

Solid dispersions of polyethylene glycol (PEG) 3000 and 10% w/w griseofulvin were prepared by the melting method. Samples were also prepared with 10% w/w of the anionic surfactant sodium dodecyl sulphate (SDS) added to the melt. Phase analysis was performed by X-ray powder diffraction and investigation of the short-range structure by 13C-CP/MAS solid-state NMR. In the samples without the added surfactant, a solid particulate dispersion of griseofulvin in PEG is obtained. The periodic structure of the pure phases is retained and so is the local structure as seen by NMR. When a surfactant is added to the dispersion a solid molecular dispersion i.e., a solid solution, is formed. The interaction between the environment and certain carbons in griseofulvin and SDS is evident. Both hydrophilic and hydrophobic parts of the molecules are influenced in a significant way. The solid solution of griseofulvin in PEG obtained on addition of SDS seems to depend on an interaction between the polymer and SDS in aggregates (micelles). These aggregates can bind griseofulvin in a molecular form at the surface or in the interior of the aggregate.