Nanocellulose–surfactant interactions

Biomass-derived nanomaterials, such as cellulose nanocrystals and nanofibrils, are attractive building blocks for the formulation of foams, emulsions, suspensions and multiphase systems. Depending on their surface chemistry, aspect ratio and crystallinity, nanocelluloses can control the rheology and stability of dispersions; they can also confer robust mechanical properties to composites. Synthetic modification of fibrillar cellulose is an option to achieve chemical compatibility in related systems, in the formation of composites, etc. However, this can also limit the environmental benefits gained from the use of the cellulosic component. Thus, an attractive mean to compatibilize and to further expand the applications of nanocelluloses is through the use of surfactants. The chemical toolbox of surfactants developed over the last 60 years allows for a large versatility while their environmental impact can also be minimized. Furthermore, relatively small amounts of surfactants are sufficient to significantly impact the interfacial forces, which has implications in material development, from the colloidal scale to the macro-scale. In this review we attempt to cover the literature pertaining to the combined uses of surfactants and nanocelluloses. We summarize reports on the incorporation with nanocellulose of nonionic, anionic, amphoteric and cationic surfactants. With the ever-expanding interest in the use of renewable materials in a vast range of applications, we hope to provide insights into the application of surfactants as a tool to tailor the compatibility and the surface chemistry of nanocelluloses.     

Membrane protein–surfactant complexes

Transmembrane proteins expose to the surrounding membrane a belt of mainly hydrophobic amino acid residues, which makes them insoluble in water. Solubilizing them and handling them in vitro generally relies on the use of dissociating surfactants (detergents). Exposing membrane proteins to detergents, however, adversely affects their stability, which is a major hindrance in their study. After briefly recalling relevant aspects of membrane protein structure, the modus operandi of detergents and the problems they raise, we describe alternative approaches such as insertion into bicelles or lipid cubic phases, or association with non-detergent amphiphiles such as peptitergents, hemifluorinated surfactants and amphipols. These novel supramolecular assemblies offer a fascinating playground for collaborative studies between organic chemists, physical chemists and biologists, and they have spurred imaginative works in each of these fields.     

Interfacial rheology of protein–surfactant mixtures

The distribution of proteins and surfactants at fluid interfaces (air–water and oil–water) is determined by the competitive adsorption between the two types of emulsifiers and by the nature of the protein–surfactant interactions, both at the interface and in the bulk phase, with a pronounced impact on the interfacial rheological properties of these systems. Therefore, the interfacial rheology is of practical importance for food dispersion (emulsion or foam) formulation, texture, and stability. In this review, the existence of protein–surfactant interactions, the mechanical behaviour and/or the composition of emulsifiers at the interface are indirectly determined by interfacial rheology of the mixed films. The effect on the interfacial rheology of protein–surfactant mixed films of the protein, the surfactant, the interface and bulk compositions, the method of formation of the interfacial film, the interactions between film forming components, and the displacement of protein by surfactant have been analysed. The last section tries to understand the role of interfacial rheology of protein–surfactant mixed films on food dispersion formation and stability. The emphasis of the present review is on the interfacial dilatational rheology.     

A fluorescence probe study of the mixed surfactant vesicles

Vesicle can be prepared from aqueous mixtures of simple commercially available, single-tailed canonic and anionic surfactants. In this work, the I3/I1 value, Ie/ Im value, and fluorescence lifetime of pyrene in different systems (see the preparation of samples) were determined. Hie essential affecting factors in the formation of vesicle can be deduced from the obtained results. It showed that large vesicle must form naturally before sonication in 0.082 M octyltrimethylammonium bromide and sodium laurate pH = 9.2 aqueous solution. While after sonication, only small vesicle exists, which can be proved further through electron microscope.     

Formation of chitosan—surfactant complexes in aqueous-alcohol media

Russian Chemical Bulletin - The complexation of chitosan and anionic surfactant, sodium dodecyl sulfate (DDS), in aqueous-alcohol media with a variable content of an organic cosolvent (methanol,...     

Thermal and structural properties of surfactant–picrate compounds

The novel surfactant?Cpicrate compounds were synthesized and characterized by thermal and XRD analysis. The synthesis, based on the electrostatic interactions of components in polar solvents, was carried out using picric acid and cationic surfactants (dodecyltrimethylammonium, didodecyldimethylammonium, and tridodecylmethylammonium halide). The idea was to investigate the dependence of physico-chemical properties and thermal transitions of picrate?Csurfactant compounds with raising number of dodecyl chains sited on the same ammoniumm head group. The equimolar mixed aqueous solutions are characterized as lyotropic, strongly promoted by picrate anion. The main crystal structure feature of investigated picrates is layered structure with stacked aromatic rings of one picrate molecule on the top of the other one via strong ?С??? interactions and connection to the alkylammonium molecules with their nitro groups by C?CH??O hydrogen bonds. Surfactant?Cpicrate bilayer-like structures are interrupted with layers of polar heads and picrate counterions and the observed width of such a bilayers are functions of more complex structural behaviors which ensures alternation in space of equal numbers of positive and negative charges. Although some of the surfactants used posses thermotropic porperties, like examined tridodecylmethylammonium chloride, no thermotropic mesomorphism is detected in solid state of investigated surfactant?Cpicrate compounds. The thermodynamic parameters of solid?Cliquid thermal transitions depend linear on the number of dodecyl chains, and for double- and triple-tailed picrate compounds the marked temporal hysteresis of the melt crystallization is registered.     

Polymer–surfactant interactions: neutron scattering and reflectivity

Recent studies of bulk and interfacial properties of polymer–surfactant systems using neutron scattering and neutron reflectivity are presented, with some discussions on a few selected systems. In bulk, the principal interests are centred on thermosensitive and hydrophobically modified associative polymers, where structural information has been used to interpret the effects of surfactants on the solubilization behavior, phase separation and gelation processes of these polymers. Conversely, the effects of polymers anchored in surfactant layers and membranes and the resulting phase changes in microemulsion systems have also received much interest. At the interface, information obtained on the structure and composition of mixed polymer–surfactant layers is discussed in relation to the surface tension and stability of these layers.     

Ionene–surfactant complexes: temperature and humidity sensitive materials

Solid stoichiometric complexes of [3,12]-ionene and dodecyl sulfate form upon reaction of the bromide of the ionene and the silver salt of dodecyl sulfate in methanol. IR, DSC, and TG investigations indicated that the solid complexes are stable between 30 and 120 °C. TG and DSC also showed that the complexes easily take up water at ambient conditions. These samples are optically isotropic. When exposed to an increased humidity they exhibit optical anisotropy, i.e., birefringence, which is caused by the formation of a hexagonal mesogenic phase. Mesogenicity is necessarily accompanied by a further uptake of water (4–5 H₂O molecules per ionic unit), which is dependent on the relative humidity. The phase behavior as a function of temperature and controlled relative humidity was studied using birefringence measurements and polarizing microscopy.     

Dispersive liquid–liquid microextraction using a surfactant as disperser agent

A novel and efficient surfactant-assisted dispersive liquid–liquid microextraction combined with high-performance liquid chromatography–photodiode array detection was developed for the determination of phenylurea herbicides in water samples. Based on this procedure, which is a dispersive-solvent-free technique, the extractant is dispersed in the aqueous sample using methyltrialkylammonium chloride. Compared with the conventional dispersive liquid–liquid microextraction, the new extraction method has many advantages such as higher extraction efficiency, low cost, reduced environmental hazards, and consumption of less extracting solvent. A few microliters of chloroform containing an appropriate amount of methyltrialkylammonium chloride (mixture of C8–C10) was used to extract the analytes from water samples. The main parameters relevant to the extraction process (namely, type of surfactant, selection of extractant solvent, extractant volume, surfactant concentration, ionic strength, and extraction time) were investigated. The performed analytical procedure showed limits of detection ranging from 2.3 to 18 ng/L, and precision ranges from 0.6% to 2.0% (as intra-day relative standard deviation, RSD) and from 1.3% to 8.3% (as inter-day RSD) depending on the analyte. The method showed good linearity between 0.04 and 40 μg/L with squared correlation coefficients better than 0.9920. This newly established approach was successfully applied to spiked real water samples.     

Formation at low surfactant concentrations and characterization of mesoporous MCM-41

At low concentrations of cetyltrimethylammonium bromide,all silica-based mesoporous materials with hexagonal phase have been synthesized via interactions between self-assembled surfactant molecule aggregates and aniomc silicate polymers.The resulting materials are characterized by XRD,FT-IR,solid state 29Si MAS NMR,thermal analysis and N2 adsorption-desorption measurements.After soluble ions are removed,the interactors between surfactant micelles and silicate polymers are reorganized and then form mesostructures 1 he hexagonal framework is sonsistent with amorphous silica gel.The structures of materials depend on the synthesis conditions Hydrothermal process improves the interactions between molecules and increases the degree of framework silicon atom polymerization The.surface area and the mesopore volume of the material prepared at 100℃ increase by 87% and 71 %,respectively,compared with those obtained at room temperature.     

A surfactant–heme–sulfonyl imidazole system as a nano-artificial enzyme

The heme–imidazole–sodium dodecyl sulfate (SDS) ternary complex has been designed as a peroxidase-like nano-artificial enzyme, in which the imidazole moiety functions like the histidine ligand in the native horseradish peroxidase (HRP) and increases the reactivity and catalytic efficiency of the designed artificial enzyme by promoting the heterolytic cleavage of hydrogen peroxide. In the present study, three different ligands were used as the imidazole-based ligands in the heme–ligand–SDS ternary system: (1) 1-methylsulfonyl-1H-imidazole, (2) 1-(benzensulfonyl)-1H-imidazole, and (3) 1-tosyl-1H-imidazole (TsIm). The three different ligands gave variable reactivity in the system studied, and the enzymatic activation parameters, using spectrophotometric measurements, showed that the TsIm ligand had a higher catalytic efficiency at 26.38 % of the native HRP efficiency. To investigate the increase in catalytic activity, its mechanism was explored based on the original mechanism of HRP and the structure of its first catalytic intermediate (compound I). Based on the mechanism of HRP and the structure of compound I, a suggested mechanism for Tslm is as follows: the TsIm cation radical makes up part of the compound I structure, which is stabilized in the enzymatic process by charge distribution that is induced via phenyl and methyl groups. Suicide inactivation of heme–TsIm–SDS and heme–imidazole–SDS models was also compared to each other. Suicide inactivation was less exhibited in the presence of TsIm than imidazole in this system unless high concentrations of hydrogen peroxide were used.     

Effect of surfactant structure on catalysis of microemulsion for photoisomerization of trans-stilbene

In this study,the photoisomerization of trans-sfilbene was carried out in water in oil (W/O) microemulsions by using sodium dodecyl sulfate (SDS),dodecyl trimethyl ammonium bromide (DTAB) and cetyl trimethyl ammonium bromide (CTAB) as surfactant,respectively.The catalytic effect of microemulsion on this reaction is closely related to the structure of surfactant.When there is no photosensitizer 9,10-dicyanoanthracene (DCA),the surfactant with shorter hydrophobic chain is preferred,while in the presence of DCA,the surfactant with anionic polar group is preferred.     

Mechanistic study of nanoparticles–surfactant foam flow in etched glass micro-models

This study was conducted in order to identify the pore-level mechanisms controlling the nanoparticles–surfactant foams flow process and residual oil mobilization in etched glass micro-models. The dominant mechanism of foam propagation and residual oil mobilization in water-wet system was identified as lamellae division and emulsification of oil, respectively. There was inter-bubble trapping of oil and water, lamellae detaching and collapsing of SDS-foam in the presence of oil in water-wet system and in oil-wet system. The dominant mechanisms of nanoparticles–surfactant foam flow and residual oil mobilization in oil-wet system were the generation of pore spanning continuous gas foam. The identified mechanisms were independent of pore geometry. The SiO₂-SDS and Al₂O₃-SDS foams propagate successfully in water-wet and oil-wet systems; foam coalescence was prevented during film stretching due to the adsorption and accumulation of the nanoparticles at the gas–liquid interface of the foam, which increased the films’ interfacial viscoelasticity.     

The shear hysteresis in lamellar structure of surfactant–water binary system

We study the shear effect on the lamellar structure of surfactants in water using dissipative particle dynamics simulations. Starting from a lamellar structure without shear flow, we increase the shear rate and then decrease it stepwisely. A weak shear changes the lamellar plane to be parallel to the shear direction though the lamellar normal has no specific direction on the plane normal to the shear direction. By increasing the shear rate, the lamellar normal eventually flips to the vorticity direction regardless of the initial configuration. Lamellar normal would stay along the vorticity direction on decreasing the shear rate. The hysteresis is also found in shear-stress. By varying the shear rate, the time needed to reach the final unique state is significantly shortened compared with that observed with a constant shear rate. We find a correlation between the excess shear-stress and the tilt angle of surfactant in lamellar.     

Effect of concentration on surfactant micelle shapes —A molecular dynamics study

Many aspects of the behavior of surfactants have not been well understood due to the coupling of many different mechanisms. Computer simulation is, therefore, attractive in the sense that it can explore the effect of different mechanisms separately. In this paper, the shapes, structures and sizes of sodium dodecylbenzenesulfonate (SDBS) micelles under different concentrations in an oil/water mixture were studied via molecular dynamics (MD) simulations using a simplified atomistic model which basically maintains the hydrophile and lipophile properties of the surfactant molecules. Above the critical micellar concentration (cmc), surfactant molecules aggregate spontaneously to form a wide variety of assemblies, from spherical to rodlike, wormlike and bilayer micelles. Changes in their ratios of the principle moments of inertia (g₁/g₃, g₂/g₃) indicated the transition of micelle shapes at different concentrations. The aggregation number of micelle is found to have a power-law dependence on surfactant concentration.     

Effect of concentration on surfactant micelle shapes——A molecular dynamics study

Above the critical micellar concentration (cmc), micelles with a wide variety of structures and shapes are formed with the increase of surfactant concentra-tion in surfactant-water or surfactant-water-oil systems, such as spherical micelles, rodlike micelles, and bilay-ers. The viewpoint that micelle should be in spheres of constant size was first proposed by Hartley[1]. Later experiments by light scatter indicated that most mi-celles were indeed spherical, and their aggregation numbers were c…     

Laser Raman spectroscopic study of water in gelatin–surfactant solutions and gels

A Raman spectroscopic study was carried out on water in gelatin at 4% w/v in gel (25 °C) and sol (40–60 °C) states at various concentrations (0.5, 1, 5, 10 and 15 mM) of anionic surfactant, sodium dodecyl sulfate (SDS). The in-phase collective stretching mode vibration of hydrogen-bonded -OH oscillators, centered around 3250 cm⁻¹ in a tetrahedral network of water molecules, was observed to be significantly affected by temperature and the presence of SDS. According to our observation this may be due to the thinning of the hydration water around the gelatin molecules due to strong thermal agitation. The peak center of the collective bands of water decreased linearly with SDS concentration in the gel state which implied that with the increase in concentration of SDS, the -OH oscillators gradually lost their attachment to gelatin chains and were replaced by SDS molecules. Ultimately this resulted in a thinning of the hydration layer around the gelatin and the oscillation frequency of -OH oscillators moved towards 3250 cm⁻¹ at 1 mM SDS concentration resulting in increased coupling of -OH oscillators to form the tetrahedral network at the critical micelle concentration (cmc) of SDS. The variation in the peak amplitudes and the systematic reversal of their trend about the cmc axis was surprising. At 40 °C the amplitude of the peak at 3250 cm⁻¹ increased drastically due to a possible coil expansion by about 7–8% which accommodated more interstitial water into the pseudonetwork leading to an increase in the number of nearest neighbors and for about 6% increase in the C value. However, at the cmc the peak amplitude was observed to be independent of temperature. Continuous shifting of the peak center and full width at half-maxima towards lower values was observed with increasing SDS concentrations in the gel state. Received: 28 September 1998 Accepted in revised form: 8 March 1999     

Topology change by screening the electrostatic interactions in a polymer–surfactant system

We show that a neutral polymer (PEG) induces a topology transition of the bilayers of an ionic surfactant system (SDS–hexanol–brine), provided that the electrostatic interactions between membranes are screened. Hexanol is used as a cosurfactant in order to get a lamellar or a sponge phase, depending on the cosurfactant/surfactant mass ratio. Using brine as solvent, the addition of polymer triggers a transformation between flat or saddle-like bilayers into vesicles. This modification is not observed in pure water because of the electrostatic repulsion between membranes. The effect can be understood in terms of the modification of the membrane Gaussian modulus due to polymer adsorption and of the entropy gain of the adsorbed polymer when the membrane bends to form a vesicle.     

Dilational properties of gemini surfactant/polymer systems at the air–water surface

The surface properties of mixed system containing gemini anionic surfactant 1,2,3,4-butanetetracarboxylic sodium, 2,3-didodecyl ester and partly hydrolyzed polyacrylamide were investigated by surface tension measurements and oscillating bubble methods. The influences of surfactant concentration, dilational frequency, temperature, pH, as well as salts on dilational modulus were explored. Meanwhile, the interfacial tension relaxation method was employed to obtain the characteristic time of surface relaxation process. The polymers play important roles in changing the interfacial properties especially at lower surfactant concentration. The possible mechanism of the polymer in changing the interfacial properties is proposed. Both the hydrophobic and electrostatic interaction among the surfactants and polymers dominate the surface properties of mixed system. These dynamic properties are of fundamental interest in understanding the structure of adsorption layers, dynamics of surfactant molecules, and their interaction with polymers at the surface.     

Thermodynamics of formation of β-cyclodextrin inclusion complexes with four series of surfactant homologs

We report on a titration microcalorimetric study of the formation of β-cyclodextrin inclusion complexes with the members of series of anionic, cationic, and nonionic surfactant homologs containing even numbers of carbon atoms in the alkyl chains. n-Alkyltrimethylammonium bromides (C_xTAB, x = 6–16), sodium n-alkyl sulfates (SC_xS, x = 6–12), sodium n-alkanesulfonates (SC_xSN, x = 6–12), and N,N-dimethylalkylamine-N-oxides (DC_xAO, x = 8–12) were selected for use. The stoichiometry, the binding constant, and the changes in enthalpy, entropy, and Gibbs free energy of the complexation reactions were determined at 298 K. It was found in each case that the complexation is favored by both the enthalpy and the entropy changes and that the thermodynamics of the process is affected far more strongly by the length of the alkyl chain than by the nature of the headgroup.