Zhao Jian-Xi

A Highly Viscoelastic Anionic Wormlike Micellar System

The rheological behavior of carboxylate gemini surfactant O,Oʹ-bis(sodium 2- tetradecylcarboxylate)-p-dibenzenediol (referred to as C14ϕ2C14) with a concentration of 140 mmol·L - 1 in aqueous solution in the presence of 100 mmol·L - 1

Effect of Sodium Salicylate on the Formation and Properties of Wormlike Micelles in Aqueous Cationic Gemini Surfactant Solutions

The effect of sodium salicylate (NaSal) on the formation and properties of wormlike micelles in aqueous solutions of 2-hydroxyl-propanediyl-α,ω-bis(dimethyldodecylammonium bromide) (12-3(OH)-12) and propanediyl-α,ω-bis(dimethyldodecylammonium bromide) (12-3-12) at a surfactant concentration of 50 mmol·L - 1 was investigated using steady-state and frequency sweep rheological measurements. In the absence of a salt, 12-3(OH)-12 or 12-3-12 only produced spherical or small rod-like micelles at 50 mmol· L - 1 . The addition of NaSal promoted micellar growth yielding wormlike micelles in both systems. 12-3 (OH)-12 showed a more sensitive response to the added NaSal compared with 12-3-12 and formed wormlike micelles at relatively lower salt concentrations. Moreover, the wormlike micelles formed by 12-3 (OH)-12 were longer than those formed by 12-3-12, resulting in higher viscosity for the former solution. These were attributed to the hydrogen bonding interactions between the hydroxyl substituted spacers in the 12-3(OH)-12 system, which increased hydration on the aggregate surface and stimulated the dissociation of counterions. The higher charge on the 12-3(OH)-12 micellar surface was strongly associated with Sal - , which led to a tighter packing of the surfactant molecules in the micelles and thus strengthened the intermolecular hydrogen bonding interactions and effectively reinforced the growth of the (Article)

Highly Viscoelastic Worm-Like Micelle Solution of Sodium Hexadecyl Sulfate Induced by Bolaform Counterions

The rheological behaviors of mixed aqueous solutions of sodium hexadecyl sulfate (SHS) and a bolaform salt, either N,Nʹ-ethanediyl-α,ω-bis(ethyldimethylammonium bromide) (Bola2Et) or N,Nʹ- propanediyl-α,ω-bis(trimethylammonium bromide) (Bola4), were investigated by steady-state and frequency- sweep measurements. The results showed that long worm-like micelles were formed in both systems at 45 °C, and the solutions exhibited high viscoelasticities, especially the SHS/Bola2Et system in which the solution had very high elasticity. The zero-shear viscosity of SHS/Bola2Et was as high as 2520 Pa·s, and the system was gel-like. These results were attributed to the formation of 2:1 complexes by electrostatic attraction. Since the spacers of both Bola counterions were shorter than the distance between quaternary ammonium ions under electrostatic equilibrium, the generated complex in shape favored formation of worm-like micelles. In comparison, it was difficult to induce SHS to form worm-like micelles by the addition of tetramethylammonium counterions, and the solution exhibited low viscosity.

Hydrophobic Synergism between the Alkyl Tails of Gemini Surfactants during Adsorption and Aggregation

The critical micelle concentration (cmc) and the concentration reducing 20 mN•m^(-1) of water surface tension (pC20) by the Gemini surfactant series (m-6-m) and the corresponding monomers (C(subscript m)TABr) were determined using surface tension measurements. Comparison between the active parameters indicates that the Gemini surfactants have a stronger micellization and adsorption ability than C(subscript m)TABr, which is attributed to the hydrophobic synergism between the alkyl tails of the Gemini surfactants. The effects of dissymmetry in the Gemini surfactants (12-6-m) on the micellization and adsorption were also discussed. The results showed that the Gemini surfactant with a symmetric structure is more effective in association and adsorption than that with a dissymmetric structure.

Determination of the Critical Micelle Concentration of Surfactant in Aqueous NaBr or n -Butanol Solution by DMABN

With p-N,N-dimethylaminobenzonitrile (DMABN) as probe, the variations of the intensity of its second fluorescence emission (Ia) and the corresponding characteristic wave-length (λa) with the surfactant (dodecyltrimethyl-ammonium bromide C12TABr, quaternary ammonium Gemini surfactant C12-3-C12·2Br and sodium dodecylsulfate SDS) concentration (c) in NaBr-containing or n-C4H9OH-containing aqueous solution were measured by a Hitachi F4500 fluorescence spectrophotometer. The results showed that the break point on the Ia-c curve and the minimum of the derivative variation corresponding to the λa-c curve agreed well with the critical micelle concentration (cmc) of the surfactant. This extends the range of DMABN as probe to measure the cmc of surfactant.