scholarly journals Segregation versus Interdigitation in Highly Dynamic Polymer/Surfactant Layers

Polymers ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 109 ◽  
Author(s):  
Omar Mansour ◽  
Beatrice Cattoz ◽  
Manon Beaube ◽  
Richard Heenan ◽  
Ralf Schweins ◽  
...  
Keyword(s):  
Weak Solution ◽  
Sodium Dodecylsulfate ◽  
Bulk Solution ◽  
Ionic Surfactants ◽  
Dodecyltrimethylammonium Bromide ◽  
Nanoscale Structures ◽  
Interfacial Structures ◽  
Surface Active ◽  
Polymer Surfactant ◽  
Active Block

Many polymer/surfactant formulations involve a trapped kinetic state that provides some beneficial character to the formulation. However, the vast majority of studies on formulations focus on equilibrium states. Here, nanoscale structures present at dynamic interfaces in the form of air-in-water foams are explored, stabilised by mixtures of commonly used non-ionic, surface active block copolymers (Pluronic®) and small molecule ionic surfactants (sodium dodecylsulfate, SDS, and dodecyltrimethylammonium bromide, C12TAB). Transient foams formed from binary mixtures of these surfactants shows considerable changes in stability which correlate with the strength of the solution interaction which delineate the interfacial structures. Weak solution interactions reflective of distinct coexisting micellar structures in solution lead to segregated layers at the foam interface, whereas strong solution interactions lead to mixed structures both in bulk solution, forming interdigitated layers at the interface.

Effect of Sodium dodecylsulfate and Dodecyltrimethyl Ammonium Bromide on the Morphologies of Gold Nanoparticles in the Presence of Poly(amidoamine) Dendrimers

2006 ◽  
Vol 6 (3) ◽  
pp. 644-650 ◽  
Author(s):  
Mandeep Singh Bakshi ◽  
Aman Kaura ◽  
Gurinder Kaur ◽  
Kanjiro Torigoe ◽  
Kunio Esumi
Keyword(s):  
Gold Nanoparticles ◽  
Aqueous Phase ◽  
Sodium Dodecylsulfate ◽  
Reducing Agent ◽  
Ionic Surfactants ◽  
Ammonium Bromide ◽  
Dodecyltrimethylammonium Bromide ◽  
Fine Gold

The synthesis of gold nanoparticles has been carried out in aqueous phase in the presence of both ionic surfactants (i.e., sodium dodecylsulfate (SDS) and dodecyltrimethylammonium bromide (DTAB)) and poly(amidoamine) dendrimers (PAMAM). It has been observed that the fluoroderivative of 2G PAMAM (2D) acts as reducing agent in reducing Au(III) to Au(0) leading to the formation of fine gold nanoparticles. This process has been further evaluated in the presence of fixed amounts of both SDS and DTAB in their respective pre and post micellar concentration regions. The presence of SDS leads to the appearance of clear ordered morphologies such as triangular, hexagonal, spherical, and rod shaped, while the presence of DTAB does not show this effect. The formation of nanoparticles in triangular morphologies is more significant in the premicellar concentration range of SDS whereas hexagonal morphologies in the post micellar concentration range. On the contrary, increase in the DTAB concentration from pre to post micellar range only reduces the size of gold nanoparticles without the appearance of any ordered morphology. The formation of ordered gold nanoparticles in the presence of SDS has been further attributed to the significant SDS-dendrimer interactions and an appropriate mechanism has been proposed to justify the results.

Aggregation Behaviours of Surface-Active Ionic Liquids 1-Alkyl-3-methylimidazolium Bis(2-ethylhexyl)sulfosuccinate

2016 ◽  
Vol 69 (11) ◽  
pp. 1254 ◽  
Author(s):  
Jiequn Wu ◽  
Tianxiang Yin ◽  
Shaoxiong Shi ◽  
Weiguo Shen
Keyword(s):  
Ionic Liquids ◽  
Self Assembly ◽  
Alkyl Chain ◽  
Systematic Investigation ◽  
Bulk Solution ◽  
Free Energies ◽  
Imidazolium Cation ◽  
Structure Transition ◽  
Surface Active ◽  
Counter Ion Binding

The systematic investigation of the aggregation behaviours of newly synthesised surface-active ionic liquids 1-alkyl-3-methylimidazolium bis(2-ethylhexyl)sulfosuccinate ([Cnmim][AOT], n = 2, 3, 5, 6, 7) by various techniques is reported. The critical aggregation concentrations (CACs) and the standard Gibbs free energies of aggregation () were determined from measurements on conductivity, fluorescence, and surface tension, which suggested a stronger self-assembly ability in the bulk solution for [Cnmim][AOT] surfactants with longer alkyl chain cations. An interesting structure transition driven by the penetration of the imidazolium cation into the aggregate when n > 4 was found by analysis of the variations of the values of CAC, , the degree of counter ion binding (β), and the micropolarity (I1/I3) immediately after the CAC with changing alkyl chain length of the imidazolium cation, which was further confirmed by 1H NMR measurements.

scholarly journals Self-assembly of sodium dodecylsulfate and dodecyltrimethylammonium bromide mixed surfactants with dyes in aqueous mixtures

2019 ◽  
Vol 6 (3) ◽  
pp. 181979 ◽  
Author(s):  
K. M. Sachin ◽  
Sameer A. Karpe ◽  
Man Singh ◽  
Ajaya Bhattarai
Keyword(s):  
Surface Tension ◽  
Self Assembly ◽  
Sodium Dodecylsulfate ◽  
Critical Micellar Concentration ◽  
Aqueous System ◽  
Mixed Surfactants ◽  
Dodecyltrimethylammonium Bromide ◽  
Aqueous Mixtures ◽  
Krafft Temperature ◽  
Vis Spectroscopy

The micellar property of mixed surfactant systems, cationic (dodecyltrimethylammonium bromide, DTAB) and anionic (sodium dodecylsulfate, SDS) surfactants with variable molar ratios in aqueous system has been reported by using surface tension and conductivity measurements at T = 293.15, 298.15 and 303.15 K. DTAB concentrations are varied from 1.0 × 10 −4 to 3 × 10 −4 mol l −1 in 1.0 × 10 −2 mol l −1 SDS solution while the SDS concentration is varied from 1.0 × 10 −3 to 1.5 × 10 −2 mol l −1 in approximately 5.0 × 10 −3 mol l −1 DTAB, so that such concentrations of DTAB-SDS (DTAB-rich) and SDS-DTAB (SDS-rich) solutions were chosen 3 : 1 ratio. The critical micellar concentration, as well as surface and thermodynamic properties for DTAB-rich and SDS-rich solutions, were evaluated by the surface tension ( γ ) and conductivity ( κ ) methods. The pseudo phase separation model was coupled with the dissociated Margules model for synergism. The Krafft temperature behaviour and optical analysis of mixed surfactants are studied using conductivity and UV–Vis spectroscopy, respectively. The dispersibility and stability of DTAB-rich and SDS-rich solutions with and without dyes (2.5 × 10 −5 mol l −1 of methyl orange and methylene blue) are carried out by using UV–Vis spectroscopy and dynamic light scattering.

scholarly journals Aerosol hygroscopicity at high (99 to 100%) relative humidities

2009 ◽  
Vol 9 (4) ◽  
pp. 15595-15640 ◽  
Author(s):  
C. R. Ruehl ◽  
P. Y. Chuang ◽  
A. Nenes
Keyword(s):  
Surface Tension ◽  
Inorganic Compounds ◽  
Droplet Diameter ◽  
Pure Water ◽  
Sodium Dodecyl ◽  
Bulk Solution ◽  
Active Compounds ◽  
Surface Active ◽  
Surface Active Compounds ◽  
Aerosol Hygroscopicity

Abstract. The hygroscopicity of an aerosol largely determines its influence on climate and, for smaller particles, atmospheric lifetime. While much aerosol hygroscopicity data is available at lower relative humidities (RH) and under cloud formation conditions (RH>100%), relatively little data is available at high RH (99.2 to 99.9%). We measured the size of droplets at high RH that had formed on particles composed of one of seven compounds with dry diameters between 0.1 and 0.5 μm, and calculated the hygroscopicity of these compounds. We use a parameterization of the Kelvin term, in addition to a standard parameterization (κ) of the Raoult term, to express the hygroscopicity of surface-active compounds. For inorganic compounds, hygroscopicity could reliably be predicted using water activity data and assuming a surface tension of pure water. In contrast, most organics exhibited a slight to mild increase in hygroscopicity with droplet diameter. This trend was strongest for sodium dodecyl sulfate (SDS), the most surface-active compound studied. The results suggest that partitioning of surface-active compounds away from the bulk solution, which reduces hygroscopicity, dominates any increases in hygroscopicity due to reduced surface tension. This is opposite to what is typically assumed for soluble surfactants. Furthermore, we saw no evidence that micellization limits SDS activity in micron-sized solution droplets, as observed in macroscopic solutions. These results suggest that while the high-RH hygroscopicity of inorganic compounds can be reliably predicted using readily available data, surface-activity parameters obtained from macroscopic solutions with organic solutes may be inappropriate for calculations of the hygroscopicity of micron-sized droplets.

scholarly journals Dispersions of Metal Oxides in the Presence of Anionic Surfactants

2018 ◽  
Vol 3 (1) ◽  
pp. 3 ◽  
Author(s):  
Leszek Ruchomski ◽  
Edward Mączka ◽  
Marek Kosmulski
Keyword(s):  
Metal Oxides ◽  
Surfactant Concentration ◽  
Critical Concentration ◽  
Supporting Electrolyte ◽  
Sodium Dodecyl ◽  
Sodium Dodecylsulfate ◽  
Solubility Limit ◽  
Ionic Surfactants ◽  
Liquid Ratio ◽  
High Concentration

We studied the behavior of dilute dispersions of nanoparticles of hematite, alumina, and titania in the presence of various concentrations of very pure sodium dodecyl-, tetradecyl-, and hexadecylsulfate. The concentrations studied were up to critical micelle concentration (CMC) for sodium dodecylsulfate, and up to the solubility limit in case of sodium tetradecyl- and hexadecylsulfate. The dispersions were adjusted to different pH (3–11), and 10−3 M NaCl was used as the supporting electrolyte. The solid-to-liquid ratio was strictly controlled in all dispersions, and the behavior of fresh dispersions was compared with dispersions aged for up to eight days. The presence of very low concentrations of ionic surfactants had rather insignificant effects on the ζ potentials of the particles. At sufficient concentrations of ionic surfactants the isoelectric point (IEP) of metal oxides shifted to low pH, and the long-chain surfactants were more efficient in shifting the IEP than their shorter-chain analogues. Once the surfactant concentration reached a critical value, the ζ potentials of the particles reached a pH-independent negative value, which did not change on further increase in the surfactant concentration and/or aging of the dispersion. This critical concentration increases with the solid-to-liquid ratio, and it is rather consistent (for certain oxides and certain surfactants) when it is expressed as the amount of surfactant per unit of surface area. Surprisingly, the surfactant-stabilized dispersions always showed a substantial degree of aggregation; that is, the particle size observed in dispersions by dynamic light scattering was higher than the size of particles observed in dry powders by electron microscopy. Apparently, in spite of relatively high ζ potentials (about 60 mV in absolute value), the surfactant-stabilized dispersions consist of aggregates rather than of primary particles, and in certain dispersions the high concentration of surfactant seems to induce aggregation rather than prevent it.

scholarly journals Fabrication of Bioactive Surfaces by Functionalization of Electroactive and Surface-Active Block Copolymers

2014 ◽  
Vol 1 (3) ◽  
pp. 134-153
Author(s):  
Omotunde Olubi ◽  
Laurisa London ◽  
Biswajit Sannigrahi ◽  
Peri Nagappan ◽  
Michael Williams ◽  
...  
Keyword(s):  
Block Copolymers ◽  
Surface Active ◽  
Bioactive Surfaces ◽  
Active Block
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