Micellization Of Gemini Surfactants Research Articles

Adsorption and Micellization of Gemini Surfactants with Diethylammonium Headgroups: Effect of the Spacer Rigidity

AbstractA series of novel cationic gemini surfactants p‐phenylenedimethylene bis(alkyldiethylammonium) chloride (abbreviated as Gm, m is the carbon numbers of hydrophobic tails) were synthesized. Their surface properties and aggregation behavior were investigated by surface tension, electrical conductivity, steady‐state fluorescence, dynamic light scattering and transmission electron microscopy measurements, and compared with gemini surfactants with a flexible hexanediyl spacer and diethylammonium headgroups [abbreviated as CmC6Cm(Et)]. It was found that Gm reached adsorption equilibrium at the air–water interface at the critical micelle concentration, but CmC6Cm(Et) did not. The packing densities and the aggregation surface charge densities of Gm are less than that of CmC6Cm(Et). Pre‐micellar association occurs in aqueous solutions of gemini surfactants with m ≥ 14. The ability to form pre‐micellar aggregates increases with increasing the length of alkyl chain. Gemini surfactants with rigid p‐xylylene spacer are more prone to form the pre‐micellar aggregates. The rigidity of the spacer of gemini surfactants has little effect on the aggregation micropolarity sensed by pyrene. Only vesicles were found in aqueous solutions of these gemini surfactants, and Gm with p‐xylylene spacer tends to form larger vesicles which have loose structures with low surface charge density.

Micellization Behavior of a Cationic Gemini Surfactant, Pentanediyl-1,5-Bis(Dimethylcetylammonium Bromide): Effect of Asparagine and Temperature

Herein, we report the effect of amino acid and temperature on the micellization of a cationic gemini surfactant, pentanediyl-1,5-bis(dimethylcetylammonium bromide), 16-5-16. In aqueous solution, the critical micelle concentration (CMC) of 16-5-16 was measured by the conductivity method at different fixed temperatures and a fixed concentration of asparagine. An increasing trend of CMC values was found with both higher (asparagine) concentrations (i.e., increases with increasing asparagine concentration) and higher temperatures (i.e., increases with increasing temperature). The thermodynamics (viz. standard Gibbs energy (#x00029;, standard enthalpy (), and standard entropy ()) of micellization of the gemini surfactant (16-5-16) were evaluated, which indicated less stability of the 16-5-16 solution in the presence of amino acid (asparagine).

Micellization of gemini surfactant with dibenzyl ether spacer in water–organic mixed media

The aggregation behavior and thermodynamics of gemini surfactant N,N′-(((1,4-phenylenebis(methylene))bis(oxy)) bis(ethane-2,1-diyl))bis(N,N-dimethyldodecan-1-aminium) (12-B-12) in a binary mixed solvent of water and organic solvents [1,4-dioxane (DO) and ethylene glycol (EG)] within the temperature range of 25°C to 40°C were investigated by the conductivity method. Micellization was delayed with the addition of organic co-solvent; consequently, a progressive increase was observed in critical micelle concentration (cmc), Gibbs free energy of micellization (ΔGm0), and Gibbs free energy of transfer (ΔGtrans0). 12-B-12 was found to be more prone to micellization in EG–water than in DO–water because of the lower cmc, more significantly negative ΔGm0, and less significantly positive ΔGtrans0. Enthalpy–entropy compensation was also investigated.

Effects of Branched-Chain Alcohols on Surface Activity and Micellization of Gemini Surfactants

Gemini surfactants are a kind of novel and efficient surfactants and alcohols are one of the most widely used additives to surfactant products in industries and daily life. Understanding the effects of alcohols on surface activities and micellization of gemini surfactants will promote the applications of gemini surfactants. Effects of linear-chain alcohol (1-pentanol) and branched-chain alcohols (2-hexanol and 3-heptanol) with the same main chain as 1-pentanol on the surface activity and micellization of cationic ammonium gemini surfactants C12CSC12Br2 (S=2, 4, 6, 8, 10, 12) in aqueous solution have been investigated by surface tension, electrical conductivity, isothermal titration microcalorimetry (ITC), cryogenic transmission electron microscopy (Cryo-TEM), and NMR techniques. The branched-chain alcohols have not shown obvious effects on the critical micelle concentration of surfactants (CMC), the size and the morphology of micelles due to loose microstructure and weak interactions between the alcohols and the gemini surfactant molecules. However, the addition of branched-chain alcohols greatly decreases the surface tension of surfactants and the surface tension decreases with the increase of the branching factor of the alcohols. In addition, the surfactant concentration required to reduce the surface tension of the solvent by 20 mN/m (C20) and the surface tension values of the surfactants at CMC (γCMC) decrease obviously with the increment of the branching factor of the alcohols at a fixed alcohol concentration due to the increase of the hydrophobic chain density at the air/solution interface. The results suggest that the branched-chain alcohols influence the self-assembly of surfactants more obviously at the air/solution interface than in micelles. Moreover, there is a second critical concentration in the surface tension curves of C12C10C12Br2 and C12C12C12Br2 with a longer spacer, indicating that the hydrophobic chains of these gemini surfactants are not packed tightly even above CMC due to the flexibility of their spacers and low CMC, and are packed more tightly with the increase of the surfactant concentration. The addition of alcohols decreases the second critical concentration remarkably with the increase of their branching factor, which means that the branched alcohols have a more obvious effect on the surface activity of gemini surfactants with a longer spacer. This work helps us to understand the effects of branched-chain alcohols on the self-assembly of gemini surfactants at air/solution interface and in bulk solution, and may provide some guidance on how to choose alcohols to adjust surface activities and micellization of gemini surfactants.

Adsorption and micellization of gemini surfactants with pyrrolidinium head groups: effect of the spacer length

A new family of gemini surfactants with pyrrolidinium head groups, 1,1′-(alkane-1, s-diyl)bis(1-dodecyl pyrrolidinium)bromide (C12–Cs–C12PB, s = 3, 4, 6, 8, 10, 12, 14, and 16), were synthesized. Their adsorption and micellization in aqueous solutions were investigated by various techniques such as equilibrium surface tension, fluorescence, and conductivity in detail. It was found that the effect of the spacer length on surfactant aggregation in aqueous solutions is similar to that of the well-known gemini surfactants with quaternary ammonium head groups (m-s-m), whereas the occupied limiting area per molecule (Amin) at the surface increases linearly with s rather than going through a maximum value at a medium value of s like that of m-s-m. The thermodynamic parameters suggest that the micellization of C12–Cs–C12PB is an entropy driven process regardless of the spacer length s. Moreover, a second breakpoint appeared in both γ–log c and I1/I3–c curves of C12–C14–C12PB and C12–C16–C12PB as the surfactant concentration increases, which can be attributed to the formation of larger aggregates. The morphology of the aggregates is confirmed by employing dynamic light scattering (DLS) and cryo-transmission electron microscopy (cryo-TEM) techniques.

Mixed Micellization of Gemini Surfactant with Nonionic Surfactant in Aqueous Media: A Fluorometric Study

Mixed Micellization of Gemini Surfactant with Nonionic Surfactant in Aqueous Media: A Fluorometric Study

Micellization of Gemini Surfactants in Polymer Solutions

Abstract The micellization behavior of three cationic gemini surfactants, C16H33N+(CH3)2(CH2)SN+(CH3)2C16H33, 2Br− (s = 4, 6, 10) have been studied in the presence of 1% (w/v) and 5% (w/v) polyethylene glycol-600 (PEG-600) by conductivity measurements at 300–320 K. From the conductivity data the critical micelle concentration, the degree of counterion ionization (α) and the thermodynamics of micellization ΔGo m, ΔHo m, ΔSo m, of the gemini surfactants have been determined. The micellar parameters show a significant dependence on the spacer length and as well as amount of polymer.