Phase and aggregation behaviour of alkylglycosides

L-Rhamnose and Phenolic Esters-Based Monocatenar and Bolaform Amphiphiles: Eco-Compatible Synthesis and Determination of Their Antioxidant, Eliciting and Cytotoxic Properties

Symmetrical and dissymmetrical bolaforms were prepared with good to high yields from unsaturated L-rhamnosides and phenolic esters (ferulic, phloretic, coumaric, sinapic and caffeic) using two eco-compatible synthetic strategies involving glycosylation, enzymatic synthesis and cross-metathesis under microwave activation. The plant-eliciting activity of these new compounds was investigated in Arabidopsis model plants. We found that the monocatenar rhamnosides and bolaforms activate the plant immune system with a response depending on the carbon chain length and the nature of the hydrophilic heads. Their respective antioxidant activities were also evaluated, as well as their cytotoxic properties on dermal cells for cosmetic uses. We showed that phenolic ester-based compounds present good antioxidant activities and that their cytotoxicity is low. These properties are also dependent on the carbon chains used.

Subcritical Methanolysis of Starch and Transglycosidation to Produce Dodecyl Polyglucosides

Biosurfactants based on carbohydrates are of special interest because of their production from renewable resources, nontoxicity, biocompatibility, and environmental friendliness. Dodecyl polyglucosides, a type of nonionic surfactant synthesized with methyl polyglucosides obtained from the eco-friendly subcritical methanolysis of renewable resource of starch, is no doubt good for ecosystem. With the subcritical methanolysis of starch, the methyl polyglucosides were obtained without any catalyst. Under the reaction condition of the weight ratio of methanol to starch of 7.5, temperature of 220 °C, and reaction time of 2 h, the yield of methyl polyglucosides was 85%. Dodecyl polyglucosides were synthesized by transglycosidation with methyl polyglucosides, and the green nonionic surfactant has excellent surface activity. The critical micelle concentration and hydrophilic lipophilic balance are 0.022 wt % and 12, respectively.

Research of Binary Surfactant Mixtures Based on N-Lauroyl Sarcosinate

Surface properties of binary surfactant systems of N-lauroyl sarcosinate (LS) with fatty alcohol polyoxyethylene ether (AEO9), dodecyl trimethyl ammonium chloride (DTAC) and dodecyl dimethyl betaine (BS-12) have been investigated in aqueous NaCl (0.1 mol · L−1) solution at (298 ± 0.1) K, respectively. Synergistic parameters of the two components in both mixed micelles and mixed adsorption layers were obtained by calculations. Furthermore, we applied the regular solution theory on the mixed systems when synergism in mixed micelle formation, surface tension reduction efficiency and surface tension effectiveness was researched. The results show that there are synergistic effects in the mixed systems, the surface performances of the mixtures are significantly better than that of any single component in the mixed systems. The result coincides with the relevant theories of the ability of mixed micelle formation, surface tension reduction efficiency and surface tension reduction effectiveness.

Improved Synthesis and Properties of N-(3-octadecylamino-2-hydroxyl) Propyl Trimethyl Ammonium Chloride

The cationic surfactant, N-(3-octadecylamino-2-hydroxyl) propyl trimethyl ammonium chloride was synthesized by an improved synthesis method and the structure was confirmed by Mass Spectrometry and 1H NMR Spectrometry. The physiochemical properties of the product were investigated systematically by surface tension and conductivity measurements. Various physiochemical parameters were calculated to evaluate the surface activities of the surfactant. The results show that both the critical micelle concentration and the degree of counterion dissociation increased with increasing temperature, but the surface tension at CMC decreased, which is opposite to that obtained on the previous condition with increasing NaCl concentration. The thermodynamic parameters obtained from conductivity measurement show that the micelle formation of the surfactant is entropy-driven in the investigated temperature range. While used as an asphalt emulsifier, N-(3-octadecylamino-2-hydroxyl) propyl trimethyl ammonium chloride exhibited an excellent emulsifying ability and it was a medium-set asphalt emulsifier.

Surface-Active Properties of a Trimeric Sulfate-type Surfactant Derived from Glycerol

A trimeric sulfate-type surfactant was synthesized and the surface chemical properties and micellar behavior of this surfactant were investigated by surface tension and fluorescence measurements. The critical micelle concentration (CMC) and the surface tension at CMC both decreased with the increase of NaCl concentration. The thermodynamic parameters indicate that the micelle formation is entropy-driven. The micelle aggregation number was determined and changed little between 303 K and 313 K. All the experimental results show that the surface-active properties of the surfactant are insensitive to the temperature compared with conventional surfactants.

Spontaneous transformation of lamellar structures from simple to more complex states

Spontaneous transformation of lamellar structures, such as multilamellar vesicles from micelles or unilamellar vesicles, is an important challenge in the field of amphiphile molecules, which may serve as models to understand biologically relevant bilayer membranes. Herein, we report a progressive self-assembly progress of N-tetradecyllactobionamide (C14G2) and tetraethylene glycol monododecyl ether (C12EO4) mixtures in aqueous solution. Increasing temperature or surfactant compositions causes spontaneous transformation from simple to high-level aggregates, i.e., from unilamellar vesicles, to coexisting multilamellar vesicles, terraced planar bilayers, and finally terraced planar bilayers. Deuterium nuclear magnetic resonance ((2)H NMR), freeze-fracture transmission electron microscopy (FF-TEM), and small-angle X-ray scattering (SAXS) measurements clearly demonstrate the spontaneously progressive self-assembly process. The interlamellar spacing (d) of the bilayers decreases from unilamellar vesicles to the terraced planar bilayers with an increase of the temperature or surfactant compositions. Lamellar samples consisting of terraced planar bilayers at higher temperature still show viscoelastic properties, being Bingham fluids, and both the viscoelasticity and yield stress increase with the composition and decrease with the temperature. The spontaneous transformation of the progressive self-assembly progress of C14G2 and C12EO4 aqueous mixtures is due to a balance of three driving forces, hydrophobic interactions, hydrogen bonding, and steric effects.

Alkali Metal Cationization of Alkyl Glucosides under Electrospray Ionization Conditions

Alkyl glucosides have been studied by electrospray ionization mass spectrometry. The effect of the hydrophobic and the hydrophilic parts of these compounds on the stability of [M + Na]+ ions has been evaluated by mass spectra at growing cone voltages. The longer the hydrophobic or the hydrophilic part, the higher the stability of these ions. It has been also found that solvent used affects the abundances of [M + Na]+ ions. In order to check if the radii of alkali metal ions influence the stability of their adducts with the compounds studied, the mass spectra have been recorded for solution containing lithium and potassium ions. The cations of smaller radius form more stable adducts, especially with the compounds having longer hydrophobic parts.

Surface Tension and Micellization of Aqueous Alkyl Polyglucosides Solutions: Influence of the Molecular Structure and the Addition of Electrolyte

Sugar-based surfactants have recently attracted considerable interest. In this work, the surface tension and critical micelle concentration (CMC) of alkyl polyglucosides (APGs) with differences in both alkyl chain lengths and average degree of polymerization (DP) were measured, and the effects of sodium chloride and sodium hydroxide on the surface tension and CMC of aqueous solutions of APGs were investigated. The alkyl chain length has a far stronger influence on the CMC than the degree of headgroup polymerization. The addition of sodium chloride to solutions of APGs has a relatively small effect compared with ionic surfactants. The observed effects of sodium hydroxide were explained in terms of the salting out of the hydrocarbon chains of APGs and the hydrotropic effect due to a negative charge on APGs micelles resulting in the deprotonation of the glucose fraction in strong alkaline system.

Alkyl Poly Glucosides (APGs) Surfactants and Their Properties: A Review

Alkyl polyglucosides are non-ionic surfactants consisting of a hydrophilic saccharide moiety and a hydrophobic fatty alkyl chain. They are synthesized from renewable raw materials and have excellent ecotoxicological profiles and are readily biodegradable. The alkyl polyglucosides are mixtures of homologues, anomers and isomers. The alkyl polyglucosides with a longer alkyl chain biodegrade faster than those with a shorter one. The short to medium alkyl chain containing alkyl polyglucosides are water soluble. They exhibit favorable wetting and surface tension reduction, electrolyte and hard water tolerance, great stability in wide pH range, synergism with other surfactants and act as hydrotropes and dispersants. The dermatological, toxicological, mildness and high compatibility to skin make alkyl polyglucosides superior to all other existing surfactants. They show good functionality in various applications like detergents, food emulsifiers, cosmetic surfactants, industrial emulsifiers and pharmaceutical granulating agents.

Unusual, pH-induced, self-assembly of sophorolipid biosurfactants

An increasing need exists for simple, bioderived, nontoxic, and up-scalable compounds with stimuli-responsive properties. Acidic sophorolipids (SL) are glucose-based biosurfactants derived from the yeast broth of Candida bombicola (teleomorph: Starmerella bombicola). The specific design of this molecule, a sophorose head with a free end-COOH group at the end of the alkyl chain, makes it a potentially interesting pH-responsive compound. We have specifically investigated this assumption using a combination of small angle neutron scattering (SANS), transmission electron microscopy under cryogenic conditions (Cryo-TEM), and nuclear magnetic resonance (NMR) techniques and found a strong dependence of SL self-assembly on the degree of ionization, α, of the COOH group at concentration values as low as 5 and 0.5 wt %. At least three regimes can be identified where the supramolecular behavior of SL is unexpectedly different: (1) at low α values, self-assembly is driven by concentration, C, and micelles are mainly identified as nonionic objects whose curvature decreases (sphere-to-rod) with C; (2) at mid α values, the formation of COO(-) groups introduces negative charges at the micellar surface inducing an increase in curvature (rod-to-sphere transition). Repulsive electrostatic long-range interactions appear at this stage. In both regimes 1 and 2, the cross-section radius of the micelles is below 25 Å. This behavior is concentration independent. (3) At α = 1, individual micelles seem to favor the formation of large netlike tubular aggregates whose size is above 100 nm. Such a complex behavior is very unique as it is generally not observed for common alkyl-based surfactants in concentration ranges below 5-10 wt %.

Use of the ternary phase diagram of a mixed cationic/glucopyranoside surfactant system to predict mesostructured silica synthesis

Mixed surfactant systems have the potential to impart controlled combinations of functionality and pore structure to mesoporous metal oxides. Here, we combine a functional glucopyranoside surfactant with a cationic surfactant that readily forms liquid crystalline mesophases. The phase diagram for the ternary system CTAB/H(2)O/n-octyl-beta-D-glucopyranoside (C(8)G(1)) at 50 degrees C is measured using polarized optical microscopy. At this temperature, the binary C(8)G(1)/H(2)O system forms disordered micellar solutions up to 72 wt% C(8)G(1), and there is no hexagonal phase. With the addition of CTAB, we identify a large area of hexagonal phase, as well as cubic, lamellar and solid surfactant phases. The ternary phase diagram is used to predict the synthesis of thick mesoporous silica films via a direct liquid crystal templating technique. By changing the relative concentration of mixed surfactants as well as inorganic precursor species, surfactant/silica mesostructured thick films can be synthesized with variable glucopyranoside content, and with 2D hexagonal, cubic and lamellar structures. The domains over which different mesophases are prepared correspond well with those of the ternary phase diagram if the hydrophilic inorganic species is assumed to act as an equivalent volume of water.

Oil-in-water nanocontainers as low environmental impact cleaning tools for works of art: two case studies

A novel class of p-xylene-in-water microemulsions mainly based on nonionic surfactants and their application as low impact cleaning tool in cultural heritage conservation is presented. Alkyl polyglycosides (APG) and Triton X-100 surfactants allow obtaining very effective low impact oil-in-water (o/w) microemulsions as alternatives to pure organic solvents for the removal of polymers (particularly Paraloid B72 and Primal AC33) applied during previous conservation treatments. The ternary APG/p-xylene/water microemulsions have been characterized by quasi elastic light scattering to obtain the hydrodynamic radius and the polydispersity of the microemulsion droplets. Laplace inversion of the correlation function CONTIN analysis provided evidence of acrylic copolymers solubilization into the oil nanodroplets. Contact angle, Fourier transform infrared (FTIR), and scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) data confirmed that microemulsions were effective in removing polymer coatings. The phase diagram of APG microemulsions showed that a reduction >90% (compared to the conventional cleaning methods) of the organic solvent can be achieved by using o/w microemulsions. The microemulsions were successfully tested in two real cases: (1) the APG based microemulsion was used in a Renaissance painting by Vecchietta in Santa Maria della Scala, Siena, Italy, degraded by the presence of a polyacrylate coating applied during a previous restoration and (2) a Triton X-100 oil-in-water microemulsion containing (NH4)2CO3 in the water continuous phase. The association of ammoniun carbonate to the microemusion led to the swelling of an organic deposit (mainly asphaltenes deposited on the fresco in the Oratorio di San Nicola al Ceppo in Florence, still contamined by the water of the Arno river during the 1966 flood) and a very efficient removal of highly insoluble inorganic deposits (mainly gypsum) strongly associated to asphaltenes. These innovative systems are very attractive for the low amount of organic solvent used to extract the polymers or highly insoluble substances as the asphaltene and the very efficient and mild impact of the cleaning procedure on the fragile painted surfaces.

Shape Dependence in the Formation of Condensed Phases Exhibited by Disubstituted Sucrose Esters

We report on the self-organizing properties of sucrose esters that are di-(1',6', 1',6, and 6,6')-substituted with aliphatic chains of identical or different chain lengths and levels of saturation. For the materials possessing two saturated aliphatic chains, the compounds exhibited thermotropic lamellar smectic A phases. A remarkable new phase transition was observed for the di-octadecanoyl homologue in which one smectic A phase transformed into another with a continuous change in layer spacing, but with a discontinuous change in the correlation length. The incorporation of long cis-unsaturated chains led to increased cross-sectional areas of the chains relative to the sucrose head groups and, hence, columnar phases were observed.

Self-Organizing Properties of Monosubstituted Sucrose Fatty Acid Esters: The Effects of Chain Length and Unsaturation

Three families of mono-substituted sucrose fatty acid esters were prepared by enzymatic and classical synthetic procedures, and their self-assembly and self-organizational properties were investigated by thermal polarised light microscopy, differential scanning calorimetry and X-ray diffraction. The properties were evaluated as a function of the fatty acid chain length. For the lower homologues of the series columnar liquid-crystalline stacking structures were found, whereas for the higher homologues, lamellar phases predominated. A model for the columnar stacking arrangement, consisting of a unique arrangement of the molecules which could lead to the creation of multiple internal ion channels between the hydrophobic interior and the hydrophilic exterior of the columns, is suggested.

Astonishing diversity of natural surfactants: 1. Glycosides of fatty acids and alcohols

Alkyl and fatty acid glycosides have become of great commercial interest in general and specifically for the pharmaceutical, cosmetic, and food industries. Natural surfactants are good sources for future chemical preparation of these glycosides. This review article shows an astonishing diversity of natural surfactants that could be used in laboratories and industry. More than 250 natural surfactants, including their chemical structures and biological activities, are described in this review article.

Interactions between n-octyl and n-nonyl β-d-glucosides and α- and β-cyclodextrins as seen by self-diffusion NMR

In this work (1)H NMR self-diffusion experiments have been performed to determine the self-diffusion coefficients of n-octyl beta-d-glucoside and n-nonyl beta-d-glucoside in alpha-cyclodextrin and beta-cyclodextrin solutions at 25 degrees C. Two questions are addressed. The first concerns the general influence on nonionic surfactant transport properties when cyclodextrins are present in solution. The second question concerns the influence of surfactant-chain length and cyclodextrin cavity volume on the association constant. The self-diffusion coefficients of the alkyl glucosides, in cyclodextrin-containing solutions, depend on the cyclodextrin concentration on account of the formation of complexes. The cyclodextrin diffusion is only mildly influenced, since the complex has similar diffusion coefficients as the free cyclodextrin. There are some obstruction effects at the highest surfactant concentrations which decrease the cyclodextrin diffusion. A set of equations to model the self-diffusion coefficients of the surfactant and cyclodextrin was developed and is presented. On the basis of such equations, properties such as association constants, and micelle and complex diffusion coefficients can be estimated.

Synthesis, preliminary characterization, and application of novel surfactants from highly branched xyloglucan oligosaccharides

A novel class of nonionic, carbohydrate-based surfactants has been synthesized from the plant polysaccharide xyloglucan. Enzymatic hydrolysis of xyloglucan yielded a series of well-defined, highly branched oligosaccharides that, following reductive amination, were readily conjugated with fatty acids bearing C8 to C18 chains under mild conditions. The critical micelle concentration, determined by tensiometry and dye-inclusion measurements, showed a typical dependence on acyl chain length and was sensitive to the degree of galactosylation of the head group. Several compounds from this new group of surfactants, especially those with C14 and C16 chains, were useful for the extraction of membrane-bound enzyme markers from different plant cell compartments in catalytically active form.