Yajie Jiang

Preparation and Performance of Catanionic Surfactants

Abstract A series of catanionic surfactants based on the general formula CH3CH2(CH2)11CH2N+(CH3)3 · −OOCCH2(CH2)nCH2CH3 (n = 2, 4, 6, 8, 10) were synthesized, and measured their critical micelle concentrations (CMC) and the corresponding surface tension at CMC (γCMC). The results revealed that the surface tensions of water were decreased to 21–34 mN · m−1 when applying these surfactants at a concentration range from 10−3 to 10−4 mol · L−1. Moreover, the performance of foaming, emulsification, anti-static and rewetting of the surfactants were investigated and the results showed that both the rewetting and emulsifying ability of the prepared surfactants were much better than that of conventional surfactants. In addition, the anti-static and foaming properties were also improved at the same condition compared to that of conventional surfactants.

Synthesis and Properties of Tetradecyltrimethylammonium Carboxylates

A series of tetradecyltrimethylammonium carboxylates based on the general formula—CH3(CH2)12CH2N+(CH3)3 · -OOCCH2(CH2)nCH2CH3 (n = 4, 6, 8) were synthesized. The tetradecyldimethylamines were quaternized with dimethyl carbonate, followed by reaction with different carboxylic acids to prepare the tetradecyltrimethylammonium carboxylates, and their structures were characterized by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. The critical micelle concentration and the minimum surface tension of these surfactants were also studied. The results indicated that the prepared surfactants could reduce the surface tension of water to 21–26 mN/m at concentration levels of 10−4 mol/L. Furthermore, their wetting ability and emulsifying ability were also investigated.

Equilibrium and dynamic surface properties of long-chain quaternary ammonium hydroxides with different chain length and number

ABSTRACT The equilibrium and dynamic surface tensions of five long-chain alkyl ammonium hydroxides (AAH) at the air/aqueous solution interface were investigated, and the effects of the length and number of alkyl chain on surface tensions had been discussed. With the increase of the length, the equilibrium surface tension (EST) increased from 28.65 to 40.52 mN/m. While, for the double chains at the critical micelle concentration (CMC), the EST decreased from 32.71 to 26.61 mN/m with the length increasing. In addition, the adsorption behaviors of the AAH were analyzed and the effective diffusion coefficients (Deff) were calculated on basis of the Ward–Tordai equation. Moreover, the time required to attain the EST decreases with the increase of surfactant concentration. The longer the C–H chain is, the lower surface tension at initial concentration is. What’s more, the diffusion processing of the AAH to air/water interface mainly depends on the surfactant concentration, and the adsorption is controlled by diffusion mechanism in a dilute concentration, while under a high concentration the adsorption is controlled by mixed diffusion–kinetic mechanism. GRAPHICAL ABSTRACT

Lipophilic counterion effect on aggregation and adsorption behavior of quaternary ammonium surfactants

ABSTRACT The obvious different aggregation and adsorption behavior of six newly quaternary ammonium surfactants with different lipophilic counterions has been discoverd by measurements of equilibrium and dynamic surface tension, fluorescence and conductivity. Interestingly, the critical micelle concentration (CMC) and its surface tension γCMC decrease with the increasing counterion chain length. However, three methods have confirmed that an exception of CMC increases slightly from C16NC1 to C16NC2. According to experimental results, a balanced mechanism between hydrophobicity and electrostatic of counterion is proposed. Besides, the dynamic surface tension results show the diffusion coefficient increases with the increasing counterion length both at a short time (Dt → 0) and long time (Dt → ∞), which indicates a faster adsorption process. Unlike the inorganic counterion, the diffusion coefficient decreases with the increase of hydrophobic chain length. This is attributed to the strong electrostatic interactions between counterions and cationic headgroups. GRAPHICAL ABSTRACT