Oxide Surfactant Research Articles

Self-diffusion in nonionic surfactant-water systems

The self-diffusion behavior of the micellar phase in some aqueous solutions of the nonionic dodecyloligoethylene oxide surfactants C 12 E 5 and C 12 R 8 was analyzed according to the cell-diffusion model. Our calculations show that the hydration number per ethylene oxide (EO) group is independent of the surfactant concentration

Complex formation between anionic polyelectrolytes and cationic/nonionic mixed micelles

Turbidimetry has been used to study the formation of complexes between anionic polyelectrolytes, i.e., poly(sodium styrenesulfonate) and poly(sodium acrylate); and cationic micelles, i.e., dimethyldodecylamine oxide, and mixed micelles of Triton X-100 and dodecyltrimethylammonium bromide. At fixed ionic strength, complex formation and concomitant phase separation occur abruptly upon increase in micelle surface charge density σ. σ is controlled by pH titration, in the case of the amine oxide surfactant, or by adjustment of surfactant composition, in the mixed micelle system. The micelle surface charge density required for phase separation increases with ionic strength. The corresponding phase boundary is a smooth line for the mixed micelle system but displays a discontinuity for the amine oxide system at conditions of pH and ionic strength where this micelle appears to undergo a sphere-rod transition. At fixed ionic strength, the mole fraction of ionic head groups in the micelle at incipient phase separation is much smaller for the amine oxide micelle than for the mixed cationic/nonionic micelle. This effect is attributed to the bulky nonionic surfactant head groups in the latter which increase the distance of closest approach between polyion segments and the ionic surfactant head groups.

The state of water in non-ionic surfactant solutions and lyotropic phases. Oxygen-17 magnetic relaxation study

Water 17O longitudinal and transverse relaxation rates have been measured in aqueous solutions and mesophases of the non-ionic alkyl oligo(ethylene oxide) surfactants C12En(n= 4, 5, 8) over wide ranges of temperature and concentration. In addition, two reference systems have been investigated: high molecular weight poly(ethylene oxide) and the dimer 1,2-dimethoxy ethane. The relaxation data are consistent with the following picture of the state of water in the headgroup shell of C12En aggregates. The shell is compact, containing less than 5 and possibly as little as 2–3 water molecules per EO group. The shell exhibits substantial structural integrity; its water content is essentially invariant with respect to changes in concentration. The headgroup shell is highly dynamic, the rate of water rotation in the shell being reduced by at most a factor of 5 (at room temperature) as compared to bulk water.

On the demonstration of bicontinuous structures in microemulsions

The problem of the demonstration of bicontinuous structures in microemulsions is critically examined, with an emphasis on systems with low concentrations of surfactant (s) and comparable volume fractions of oil and water. While the problem of microemulsion bicontinuity has been investigated by a large number of experimental approaches, it is found that to date, only a few can provide an unambiguous clarification of this point. Multicomponent self-diffusion data appear to provide the most convenient and reliable examination of the problem, and therefore the possibilities and limitations of this approach are analysed in some detail. From experimental studies it is found that microemulsions with approximately equal volume fractions of the two solvents are in general bicontinuous, also in the most narrow sense of the word. It is also demonstrated that surfactant molecules in these microemulsions are arranged in monomolecular layers, which are characterized by a spontaneous packing into surfaces of zero, or at least low, mean curvature. The relation between surfactant packing characteristics and microemulsion structure is discussed, in particular for the typically observed sequence of curvature towards oil ⪢ zero mean curvature ⪢ curvature towards water, on change of some parameter (e.g., salinity, cosurfactant, surfactant composition, temperature). As regards an understanding of the physical mechanisms behind alterations in surfactant packing (and thus also microstructure), the problem of nonionic oligo (ethylene oxide) surfactants appears to provide the most intriguing (and controversial) problem. This problem is therefore discussed in a slightly broader context.

Interaction between amine oxide surfactant layers adsorbed on mica

A surface-force apparatus has been used to determine the interaction between two mica surfaces immersed in water solutions of a non-ionic surfactant dimethyldodecylamine oxide (DDAO). These interactions could be associated with three different adsorption states as the surfactant concentration was increased : hardly any adsorbed surfactant, a monolayer and a bilayer. The study has also been aimed at determining any temperature dependence in the interactions between bilayer-coated surfaces. In addition to the surface-force measurements. quantifications of the amount of adsorbed surfactant on mica sheets were made using X-ray photoelectron spectroscopy. The contact angles were also determined for the same mica samples. From these results we suggest an adsorption mechanism based on positively charged surfactant molecules adsorbing into the negatively charged mica substrate. No temperature dependence is found of the forces between bilayer-coated surfaces and this is consistent with the absence of any temperature-induced phase separation of the DDAO–water system.

Surfactant Solution Transport in Wool Yarn

The immersion absorption of a wool carpet yarn was studied to gain a better understanding of yarn scouring processes. Upon initial immersion in nonylphenol poly(ethylene oxide) (NPEO) surfactant solutions at 50°C, yarn bundles became rapidly and almost completely saturated. After removal from the solution and squeezing, however, complete absorption on subsequent immersions in either an identical solution or distilled water was possible only when the EO chain length of the NPEO surfactant was ≥ 12. For an EO chain length of 9, complete saturation on the subsequent immersions was possible only when the surfactant concentration was <0.5 gl-1. Evidence suggests that the incomplete saturation phenomenon is caused by thin surfactant films that trap air in the yarn interior. The thin films are formed in the squeezing process following the first immersion.

Surfactant Solution Transport in Wool Yarn

Surfactant solution transport rates were measured on wool yarn scoured or otherwise treated with various nonylphenol poly(ethylene oxide) (NPEO) surfactants or with the sodium salt of dioctyl sulfosuccinate. The EO chain length of the NPEO used to scour the yarn had a significant effect on the diffusivity coefficient, although not on the residual contaminant level or the color. Surfactants applied as prewetting or rewetting agents increased the diffusivity coefficients. Prewetting gives the faster solution transport rates, and the temperature of application and the wet add-on are important. The effectiveness of a rewetting agent is related to its rate of solution.

Double-label time-resolved immunofluorometry of lutropin and follitropin in serum.

We describe a procedure for the simultaneous immunofluorometric assay of lutropin and follitropin in human serum, based on the use of monoclonal antibodies and of the fluorescent lanthanides Eu3+ and Tb3+. The alpha-chain-specific antibody was used as a common capture antibody on the surfaces of microtitration strips. The anti-beta-follitropin antibody was labeled with Tb3+, the anti-beta-lutropin antibody with Eu3+. After the immunoreactions had taken place, the bound fractions of the labels were dissociated in a fluorescence enhancement solution of pivaloyltrifluoroacetone, trioctylphosphine oxide, and Triton X-100 surfactant. In this solution both lanthanides can be measured successively with a time-resolved fluorometer. The detection limit of the assay is 0.1 int. unit/L for lutropin and 1 int. unit/L for follitropin. Results correlated well with those by commercial immunofluorometric assays and radioimmunoassays.

Aging of micellar solutions of ethylene oxide surfactants

Aging of micellar solutions of ethylene oxide surfactants

Surfactant Solution Transport in Wool Yarn

The transport of nonylphenol poly(ethylene oxide) surfactant solutions in bundles of wool carpet yams was studied and the kinetics were found to conform to Fick's law. Yam contaminants (residual wool grease and water soluble spinning lubricant) had a major effect on the diffusivity coefficients. The detergency of residual wool grease was involved in the solution transport and was probably the rate-determining step. Scoured and unscoured yams behaved differently: scoured yarn was wetted most rapidly by a surfactant with an EO/NP ratio of 9, while unscoured yam wetted most rapidly when the EO/NP was 12. The rate of solution transport in scoured yam in creased greatly with surfactant concentration but little with temperature, while the converse held for unscoured yarn.

Effects of a homogeneous linear alcohol ethylene oxide surfactant on the ultrastructure of soybean cell suspension cultures

Ultrastructural alterations of soybean cell suspension cultures treated with a homogeneous linear alcohol ethylene oxide nonionic surfactant, the octa(oxyethylene) adduct of 1-dodecanol (at concentrations below the critical micelle concentration), were determined at 0.5, 3, and 10 days. Treatments were 4 μM (2 ppm; nonphytotoxic), 11 to 17 μM (6 to 9 ppm; inhibitory), and 28 μM (15 ppm; phytotoxic). Plastids and mitochondria appeared to have reduced amounts of internal membranes at 0.5 days, even at sublethal concentrations. At 3 days after treatment, cells treated with up to 17 μM detergent looked similar to control cells, except for void regions in some organelles. Cells treated 0.5 days with 28 μM had plastids with few membranes and much reduced starch compared with controls; by 3 days, these cells were badly damaged, although numerous organelles still could be recognized and lipid bodies were spherical. Distinctive myelin-like membrane whorls were present in some 3-day 28 μM treated cells. Even at 10 days recognizable organelles in cells included nuclei, plastids, some endoplasmic reticulum and some flattened nuclei with irregularly shaped nucleoli. Starch granules were conspicuously free of the plastids in which they were formed. Lipid bodies were often angular in shape rather than spherical. Outer envelopes of organelles often remained, even though their internal structures were destroyed or altered greatly.

Synthesis and properties of 2‐alkoxy‐N, N‐Dimethylethylamine N‐oxides

Abstract2‐Alkoxy‐N,N‐dimethylethylamines (1) were prepared from the reaction of alkyl chlorides with 2‐dimethylaminoethanol in the presence of potassium hydroxide. Amine oxide surfactants 2 were prepared by oxidation of1 with hydrogen peroxide. The surfactants 2 were good foam stabilizers and stable up to 100 C, but decomposed rapidly to vinyl ethers at 150 C.

Interacting C n E m non-ionic micellar systems

Trends in the temperature dependence of the effective intermicellar attraction ε(T) have been calculated for a series of non-ionic ethylene oxide surfactants CnEm[CnH2n+ 1(OCH2CH2)mOH] using the penetrable-sphere model of Widom and Rowlinson to model the cloud curve. The form of ε(T) may be analytically related to the critical exponent and to the shape of the coexistence curve close to the lower consolute solution temperature in the mean-field approximation. The results show that ε(T) calculated from the scaled cloud curves increases more rapidly with temperature as the alkyl chain length is varied over the range n= 8, 10, 12 and 16 while little effect of headgroup size is seen in the range of m available. The application of the concept of corresponding states to these systems is discussed and the results are related to two recent alternative approaches and to the experimental evidence for the characterisation of the structure of CnEm micelles.

Nuclear magnetic resonance technique to distinguish between micelle size changes and secondary aggregation in anionic and nonionic surfactant solutions

The presence of surfactants in large micelles gives rise to broad n.m.r. resonances because of the long correlation time for diffusion around the micelle. This has been used to investigate the structure of surfactant aggregates in systems where other evidence indicates that large micelles occur. For polyethylene oxide surfactants at the cloud point, the surfactant micelles are small and the large units are formed by secondary aggregation of small micelles. For sodium dodecylsulphate with added salt, octanol or other surfactants, large micelles are formed. The changes in micelle size indicated by changes in n.m.r. linewidths are in agreement with changes measured by the quasi-elastic light scattering technique.

Uptake and movement of paraquat in cocksfoot and wheat as influenced by surfactants

AbstractSurfactants are used to increase the efficiency of herbicide formulations mainly because they wet out leaf surfaces, thereby stabilising and increasing the contact area of droplets on the surface. Herbicide penetration through the cuticle may also be facilitated.The work described eliminates effects on wetting and contact area in order to study the effect of surfactants on the penetration and movement of paraquat in cocksfoot. Surfactants were various types of alcohols and amine oxides condensed with 2 to 30 moles of ethylene oxide used at 0.1 to 0.5%. An adult leaf of cocksfoot (Dactylis glomerata) was immersed briefly to constant area in paraquat solutions containing surfactant and uptake and movement of paraquat is recorded.Uptake was little affected by differences in surfactant structure except where surface activity was low and solutions failed to wet out the leaf surface. Percentage movement with 0.5% surfactant was often less than that with 0.1% and a high ethylene oxide content also reduced percentage movement. Paraquat activity was influenced by both the degree of uptake and movement, but movement was the greater influence.Amine oxide surfactants reduced movement less than those based on alcohols. The action of surfactants is discussed in terms of a hydrophobic/hydrophilic balance in the surfactant molecule.

The effects of small ions and long-chain alkyl ions on the potentiometric behavior of micelles of dimethyldodecylamine oxide

The effects of small ions ( z + z − electrolytes) and long-chain alkyl ions (ionic surfactants) on the surface potential ψ 0 of the micelle of a cationic-nonionic surfactant, dimethyldodecylamine oxide, have been studied by potentiometric titrations of its micellar solutions. The effect of small ions on ψ 0 is in accord with the effect predicted from the Gotüy-Chapman equation for spherical particles. Small counter-ions, especially their valences, have considerable influence on ψ 0 whereas co-ions have no remarkable influence. The effect of long-chain alkyl ions on ψ 0 is directly related to the charge properties of the added surfactant, probably owing to the formation of mixed micelles with the amine oxide surfactant.

An Integrally Coloured Polyethylene Oxide Surfactant

The synthesis of 0 polyethylene oxide surfactant having an integrally joined aza dyestuff is described. The method has general application. The new dye-polymer (IV) will be useful for adsorptiostudies with silver halides.