Sugar-based Gemini Surfactants Research Articles

Synthesis and Aggregation of Novel Sugar-based Gemini Surfactants in Aqueous Solution

Abstract Novel sugar-based gemini surfactants with a 1,3-propan-2-ol spacer (1, 3-(N- alkyl-2-D-glucosaminyl acetyl) propan-2-ol, Glu(n)-3(OH)-Glu(n), n = 12, 14) were synthesized with D-(+)-glucono-1,5-lactone as starting material in two steps, whose structures were confirmed using proton nuclear magnetic resonance spectroscopy (1H NMR) and carbon nuclear magnetic resonance carbon spectroscopy (13C NMR). The micellization of Glu(n)-3(OH)-Glu(n) (n = 12, 14) in aqueous solution at 25.0°C was investigated by using surface tension measurement. The results show that the critical micelle concentration (CMC) of Glu(12)-3(OH)-Glu(12) is around 10–5 mol × L–1, and is one order of magnitude smaller than that of Glu(14)-3(OH)-Glu(14), indicating that the surface activity of Glu(12)-3(OH)-Glu(12) is superior to that of Glu(14)-3(OH)-Glu(14). Moreover, the aggregation behavior of Glu(12)-3(OH)-Glu(12) in aqueous solution at different pH values was investigated by surface tension, dynamic light scattering (DLS), and cryogenic transmission electron microscopic (Cryo-TEM) measurements. The results indicate that the CMC slightly increases with the decrease of the solution pH. The microstructure of Glu(12)-3(OH)-Glu(12) aggregates transitions from micelle to vesicle with the solution pH from acidic to neutral and alkaline. The microstructural transformation of Glu(12)-3(OH)-Glu(12) with the solution pH is mainly determined by the protonation of the two tertiary amine nitrogen atoms in its hydrophilic headgroups.

Surface modification of poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) elastomer via covalent immobilization of nonionic sugar-based Gemini surfactants

Gemini surfactants (GS) with sugar-containing head-groups and different alkyl chains were successfully prepared. Poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) elastomer was grafted with glycidyl methacrylate (GMA) by means of UV-induced graft polymerization, and then the pGMA-grafted film was chemically immobilized with the GS. The surface graft polymerization was confirmed by ATR-FTIR and XPS. The wettability and hemocompatibility of the modified surface were characterized by means of water contact angle, protein adsorption, and platelet adhesion assays. The results showed that amphiphilic surfactant-containing polymer surfaces presented protein-resistant behavior and anti-platelet adhesion after functionalization with GS, GS1 and GS2. Besides, the hemocompatibility of the modified surface deteriorated as the length of hydrophobic chain of GS increased.

Equilibrium Surface Tension, Dynamic Surface Tension, and Micellization Properties of Lactobionamide-Type Sugar-Based Gemini Surfactants

A sugar-based gemini surfactant N,N'-dialkyl-N,N'-dilactobionamideethylenediamine (2C(n)Lac, where n represents alkyl chain lengths of 8, 10, 12, and 14) was synthesized by reacting N,N'-dialkylethylenediamine with lactobionic acid. The adsorption properties of 2C(n)Lac were characterized by equilibrium and dynamic surface tension measurements. Their micellization properties were investigated by steady-state fluorescence using pyrene as a probe and dynamic light scattering (DLS) techniques. The dependence of these properties on the alkyl chain length and the number of sugars was determined through a comparison with the corresponding monomeric surfactants C(n)MLA and previously reported sugar-based gemini surfactants containing monosaccharide gluconamide or disaccharide lactobionamide groups with a hexanediamide spacer. The critical micelle concentration (cmc) and surface tension of 2C(n)Lac are both lower than those of C(n)MLA surfactants. These lower values indicate that the synthesized sugar-based gemini surfactants have excellent micelle-forming ability in solution and high adsorption ability at the air-water interface, which result from strong interactions of the hydrogen bonds between the hydroxyls in lactobionamide groups. When the alkyl chain length of 2C(n)Lac increases to 14, premicellar formation occurs in the solution along with adsorption at the air-water interface at concentrations below the cmc. Furthermore, 2C(n)Lac forms micelles measuring 4 to 12 nm in solution, with no dependence on the alkyl chain length, and their size slightly increases with increasing concentration.

Adsorption characteristics of sugar-based monomeric and gemini surfactants at the silica/aqueous solution interface

The adsorption behavior of sugar-based surfactants at the silica/aqueous solution interface has been characterized on the basis of the adsorption isotherm, ζ potential and in situ atomic force microscopy (AFM) data. The surfactants used in the current work are monomeric Glu( n) ( N-alkyl- N-methylgluconamide) and gemini Glu( n)-2-Glu( n) ( N, N′-dialkyl- N, N′-digluconamide ethylenediamine), where n is the hydrocarbon chain length of 10 and 12. The adsorption isotherm reveals that, for all the surfactants, the adsorbed amount increases even above the critical micelle concentration (cmc) and an adsorption plateau region appears at the equilibrium concentration well above the cmc. The driving force for this adsorption is deemed to be a combination of the hydrogen bonding between the sugar moieties and the surface silanol groups and the intermolecular hydrophobic interaction of free monomers to the surfactants pre-adsorbed on silica. In the adsorption plateau region, the occupied area per molecule adsorbed on silica is calculated to be generally larger for the gemini surfactants than for the monomeric ones. This reflects the bulky structure of the headgroups of the sugar-based gemini surfactants and/or the relatively less favorable interaction of the headgroups with the silica surface. The combination of the soft-contact AFM and force curve data suggests that a structural transformation of the adsorbed layer occurs with an increase in the surfactant concentration, depending on the packing parameter of each surfactant. At the concentration above the cmc, the monomeric surfactants form either worm-like surface micelles or a patchy bilayer whereas the gemini surfactants only form a patchy bilayer.

Adsorption and micellization behavior of novel gluconamide-type gemini surfactants

The adsorption and micellization behavior of novel sugar-based gemini surfactants ( N , N ′ -dialkyl- N , N ′ -digluconamide ethylenediamine, Glu( n)-2-Glu( n), where n is the hydrocarbon chain length of 8, 10 and 12) has been studied on the basis of static/dynamic surface tension, fluorescence, dynamic light scattering (DLS) and cryogenic transmission electron microscope (cryo-TEM) data. The static surface tension of the aqueous Glu( n)-2-Glu( n) solutions measured at the critical micelle concentration (cmc) is observed to be significantly lower than that of the corresponding monomeric surfactants. This suggests that the gemini surfactants, newly synthesized in the current study, are able to form a closely packed monolayer film at the air/aqueous solution interface. The greater ability in the molecular association is supported by the remarkably (approximately 100–200 times) lower cmc of the gemini surfactants compared with the corresponding monomeric ones. With a combination of the fluorescence and DLS data, a structural transformation of the Glu( n)-2-Glu( n) micelles is suggested to occur with an increase in the concentration. The cryo-TEM measurements clearly confirm the formation of worm-like micelles of Glu(12)-2-Glu(12) at the concentration well above the cmc.

Synthesis and Properties of Sugar-Based Gemini Surfactants

Abstract A series of new gemini surfactants having hydrophilic glucosides were synthesized from glucose via two different synthesis roads, including N,N′-didodecyl-N,N′-bis-(1-glucosyl-2-hydroxyl-propyl)-p-phthaloyl amide [B(DG)PA], N,N′-didodecyl-N,N′-bis(1-glucosyl-2-hydroxyl-propyl)-2,5-dicarboxylate p-phthaloyl amide [B(DGC)PA], N,N′-didodecanoyl-N,N′-bis-(1-glucosyl-2-hydroxyl-propyl) ethylenediamine [B(DG)EA], and N,N′-didodecanoyl-N,N′-bis-(1-glucosyl-2-hydroxyl-propyl) hexanediamine [B(DG)HA]. The final products were characterized by IR and NMR spectral measurements and by interfacial tension measurements. The critical micellar concentrations (cmc) of these gemini surfactants were determined to be 2.49 × 10−6, 1.93 × 10−6, 2.47 × 10−6 and 1.66 × 10−6 mol L−1, respectively, which are about one order of magnitude lower than the corresponding monomeric surfactants (GHPDA). The results showed that these synthesized sugar-based gemini surfactants had high abilities to reduce the surface or oil-water interface tension. The high surface activity of these synthesized molecules was attributed to their unique structure where two optimally spaced hydrophobic chains and hydrophilic groups were present.

PH-Dependent Aggregation Properties of Mixtures of Sugar-Based Gemini Surfactants with Phospholipids and Single-Tailed Surfactants

Sugar-based gemini surfactants (GSs) display rich pH-dependent phase diagrams and are considered to be promising candidates as gene- and drug-delivery vehicles for biomedical applications. Several sugar-based GSs form vesicles around neutral pH. The vesicular dispersions undergo transitions toward wormlike micelles and spherical micelles at acidic pH, whereas flocculation followed by redispersion upon charge reversal is observed at basic pH. The influence of various amounts of the double-tailed phospholipids DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine) and DOPE (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) and of the single-tailed surfactants lyso-PC (1-palmitoyl-2-hydroxy-sn-glycero-3-phosphocholine) and OTAC (octadecyltrimethylammonium chloride) on the phase behavior of GS1 (1,8-bis(N-octadec-9-yl-1-deoxy-D-glucitol-1-ylamino)3,6-dioxaoctane) was determined as a function of pH, in water and in water at physiological ionic strength. The pH corresponding to the phase transitions and the characteristics of the aggregates were determined by means of a combination of physical techniques: static and dynamic light scattering (SLS and DLS), fluorescence spectroscopy, cryo-TEM and diffusion- and (31)P NMR. The results show that the additives affect the phase behavior of the GS1 dispersions in a pH-dependent fashion. In the presence of double-tailed phospholipids, a higher degree of protonation of GS1 must be reached to observe micelle formation, whereas single-tailed surfactants affect these transitions only slightly. In the presence of increasing amounts of lyso-PC, the pH range of flocculation becomes more narrow, indicating the increased hydration of the vesicles. The pH of redispersion after charge reversal is particularly sensitive to the presence of positively charged additives. It is suggested that the cationic headgroups disturb the hydrogen-bond structure of water at the vesicular surface, hampering OH(-) binding. The effect of an increase in ionic strength to physiological values is found to be modest, except for the dispersions containing the positively charged additives.

Sugar-Based Gemini Surfactants with Peptide Bonds─Synthesis, Adsorption, Micellization, and Biodegradability

The sugar-based gemini surfactant with peptide bonds, N,N'-bisalkyl-N,N'-bis[2-(lactobionylamide)ethyl]hexanediamide (2C(n)peLac, in which n represents hydrocarbon chain lengths of 12 and 16), was synthesized by reacting adipoyl chloride with the corresponding monomeric surfactant N-alkyl-N'-lactobionylethylenediamine (C(n)peLac), which was obtained by reacting ethylenediamine with alkyl bromide and lactobionic acid. The adsorption and micellization properties of C(n)peLac and 2C(n)peLac were characterized by the measurement of their equilibrium and dynamic surface tension, steady-state fluorescence using pyrene as a probe, dynamic light scattering (DLS), and time-resolved fluorescence quenching (TRFQ), and their biodegradability was also investigated. The critical micelle concentration (cmc) decreases with an increase in the hydrocarbon chains from monomeric to gemini surfactants, whereas it increases with an increase in the chain length from 12 to 16 for both systems. The increases in both the hydrocarbon chain and the chain length of sugar-based surfactants reduce surface activities such as the ability to lower the surface tension, the occupied area per molecule, and the adsorption rate at the air/water interface. The sugar-based surfactants C(n)peLac and 2C(n)peLac exhibit unique aggregation behavior in aqueous solution. The DLS results indicate that the apparent hydrodynamic diameter of C(n)peLac micelles decreases sharply with increasing concentration, whereas that of 2C(n)peLac micelles decreases gradually. From the TRFQ measurement, it was observed that, as concentration increases, the aggregation numbers are almost constant for C(n)peLac, whereas they increase for 2C(n)peLac. These results imply that loosely packed micelles formed by sugar-based surfactants become tightly packed micelles as the concentration increases. Furthermore, it was found that 2C(n)peLac shows lower biodegradability than does C(n)peLac because it contains tertiary amines in the molecule.

Sugar-based gemini surfactant with a vesicle-to-micelle transition at acidic pH and a reversible vesicle flocculation near neutral pH.

A sugar-based (reduced glucose) gemini surfactant forms vesicles in dilute aqueous solution near neutral pH. At lower pH, there is a vesicle-to-micelle transition within a narrow pH region (pH 6.0-5.6). The vesicles are transformed into large cylindrical micelles that in turn are transformed into small globular micelles at even lower pH. In the vesicular pH region, the vesicles are positively charged at pH < 7 and exhibit a good colloidal stability. However, close to pH 7, the vesicles become unstable and rapidly flocculate and eventually sediment out from the solution. We find that the flocculation correlates with low vesicle zeta-potentials and the behavior is thus well predicted by the classical DLVO theory of colloidal stability. Surprisingly, we find that the vesicles are easily redispersed by increasing the pH to above pH 7.5. We show that this is due to a vesicle surface charge reversal resulting in negatively charged vesicles at pH > 7.1. Adsorption, or binding, of hydroxide ions to the vesicular surface is likely the cause for the charge reversal, and a hydroxide ion binding constant is calculated using a Poisson-Boltzmann model.

Synergistic Effects of Alkyl Glucosides and Nonionic Sugar-Based Gemini Surfactants

Synergistic Effects of Alkyl Glucosides and Nonionic Sugar-Based Gemini Surfactants