Zhinong Gao

Surface Tension and Aggregation Properties of Novel Cationic Gemini Surfactants with Diethylammonium Headgroups and a Diamido Spacer

A series of novel cationic gemini surfactants with diethylammonium headgroups and a diamido spacer were synthesized, and their surface and bulk properties were investigated by surface tension, electrical conductivity, fluorescence, viscosity, dynamic light scattering (DLS), and transmission electron microscopy (TEM) measurements. An interesting phenomenon, that is, the obvious decline in surface tension upon increasing concentration above the critical micelle concentration (cmc), was found in these gemini surfactant solutions, and two explanations were proposed. This surface tension behavior could be explained by the rapid increase in the counterion activity in the bulk phase or the continued filling of the interface with increasing surfactant concentration above the cmc. More interestingly, not only vesicles but also the surfactant-concentration-induced vesicle to larger aggregate (spongelike aggregate) transition and the salt-induced vesicle and spongelike aggregate to micelle transition were found in the aqueous solutions of these gemini surfactants. The spongelike aggregate that is first reported in the cationic gemini surfactant-water binary system is probably caused by the adhesion and fusion of vesicles at high surfactant concentration.

Synthesis and surface activity of biquaternary ammonium salt gemini surfactants with ester bond

The synthesis and surface activity of gemini surfactants with ester bond as spacer are described. Their critical micelle concentrations (CMC) are much lower than that of conventional surfactants, i.e., 1.62×10−5, 1.38×10−5, 1.28×10−5 mol · L−1 for gemini I, II and III respectively. Surface tension at the CMC of gemini I, II and III were 36.4, 38.5, 41.2 mN · m−1. The physico-chemical properties such as Krafft points, foaming abilities and emulsifying power were also investigated. It is found that the title compounds have low Krafft points and show good solubility in water. The gemini surfactants synthesized also exhibit good foaming properties and excellent emulsifying power toward toluene. The foaming abilities and emulsifying power increase with the increase in carbon number of hydrophobic chain, and this might be caused by the sheer viscosity of different gemini surfactant solution.

Effect of hydrocarbon structure of the headgroup on the thermodynamic properties of micellization of cationic gemini surfactants: An electrical conductivity study

A series of cationic gemini surfactants butanediyl-1,4-bis(dodecyldialkylammonium bromide), C(12)H(25)N(+)(C(m)H(2)(m)(+1))(2)C(4)H(8)N(+)(C(m)H(2)(m)(+1))(2)C(12)H(25)·2Br(-), where m=1, 2, 3, 4, referred to as C(12)C(4)C(12)(Me), C(12)C(4)C(12)(Et), C(12)C(4)C(12)(Pr), and C(12)C(4)C(12)(Bu), respectively, were synthesized, and their thermodynamic properties of micellization were studied by electrical conductivity measurements. There existed a minimum critical micelle concentration (cmc) in the curve of cmc versus temperature, and the temperature of the minimum of cmc (T(min)) increased with increasing the headgroup alkyl chain length. The values of log (cmc) depended linearly on carbon number of the alkyl chains, but that was not true for the carbon number of the headgroup substituents. The temperature dependence of cmc and degree of counterion association (β) were used to calculate the Gibbs free energy (Δ(mic)G°), enthalpies (Δ(mic)H°) and entropies (Δ(mic)S°) of micelle formation for these gemini surfactants, and well correlated enthalpy-entropy compensation was observed. The analyses showed C(12)C(4)C(12)(Me) and C(12)C(4)C(12)(Et) behaved similarly in terms of thermodynamics of micellization, but they behaved differently from C(12)C(4)C(12)(Pr) and C(12)C(4)C(12)(Bu), which could be ascribed to the hydrophobicity and the location of the headgroup alkyl chains in the aggregates. These initial results indicate the headgroup alkyl chain plays an important role in influencing the thermodynamic properties of gemini surfactants.

Correction to “Rational Design and Synthesis of Carboxylate Gemini Surfactants with an Excellent Aggregate Behavior for Nano-La2O3 Morphology-Controllable Preparation”

A series of carboxylate gemini surfactants (CGS, Cn-Φ-Cn, n = 12, 14, 16, 18) with diphenyl ketone as a spacer group were prepared using a simple and feasible synthetic method. These CGS exhibited an excellent surface activity with extremely low critical micelle concentration (CMC) value (approximately 10–5 mol/L), good performance in reducing surface tension (nearly 30 mN/m), and the ability of molecular self-assembly into different aggregate morphologies via adjusting the concentrations, which is attributed to the introduction of diphenyl ketone and carboxylic acid ammonium salt in the molecular structure. Moreover, the surface activity and self-assembly ability of CGS were further optimized by tuning the length of the tail chain. These excellent properties imply that CGS can be a soft template to prepare nanomaterials, especially in morphology-controllable synthesis. By adjusting the concentration of one of CGS (C12-Φ-C12), nano-La2O3 particles with diverse morphologies were obtained, including spheric...