Qiuxiao Li

Adsorption and aggregation properties of novel star-shaped gluconamide-type cationic surfactants in aqueous solution

The adsorption and aggregation behavior of novel star-shaped gluconamide-type cationic surfactants N-dodecyl-N,N-bis[(3-D-gluconylamido)propyl]-N-alkylammonium bromide (CnDBGB, where n represents hydrocarbon chain lengths of 10, 12, and 14) has been studied on the basis of static/dynamic surface tension, conductivity, dynamic light scattering (DLS), and transmission electron microscopy (TEM) data. The static surface tension of the CnDBGB aqueous solution measured at the critical micelle concentration (CMC) is observed to be significantly lower than that of the corresponding monomeric surfactants. The dynamic surface tension results indicate that adsorption process of above CMC is a mixed diffusion–kinetic adsorption mechanism. From the results of temperature dependent conductivity measurements, we could obtain the degree of counterion binding (β) and the thermodynamic parameters such as standard free energy (ΔGmic0), enthalpy (ΔHmic0), and entropy (ΔSmic0) of aggregation. With a combination of the DLS and TEM data, a size transformation of the micelles is suggested to occur with an increase in the concentration.

Effect of Borax on the Solubility of Dicephalic Gluconamide-Type Surfactants

The dicephalic gluconamide-type surfactant (C12-DGA) was synthesized and characterized by FTIR, 1H NMR spectrometry. The impacts of added amount of borax on solubility of C12-DGA at room temperature were investigated. Surface activities and aggregation behavior in aqueous solution of mixed C12-DGA-borax were investigated by surface tension measurements, dynamic light scattering (DLS) and transmission electron microscopy (TEM). It is found that borax was a good solubilizing agent for C12-DGA, and surface tension and cmc of the C12-DGA has little influence when the molar ratio of C12-DGA and borax was higher than 20:1. Interestingly, morphology transformation from necklace-like micelles to rod-like nanostructure and spherical micelle was observed during the incubation procedure.

Effect of Temperature and Added Counter Ions on Micelle Formation of Guanidine Surfactants

Abstract Electrical conductivity was measured for aqueous solutions of long-chain guanidine surfactants (G12 and MG12) at different temperatures and with various added counter ions. The critical micelle concentration (cmc) of these surfactants determined from the specific conductivity (κ) vs. concentration (c) plot is lower than those of the typical cationic surfactants, such as alkyltrimethylammonium chloride with the same hydrocarbon chain length. The electrical conductivity data were analyzed according to the mixed electrolyte model of micelle solution, and the degree of counter ion binding (β) was calculated. The thermodynamic parameters for micelle formation were estimated using the values of cmc and β as a function of temperature. The more negative ΔGmic for MG12 indicates more favored micellization. The contribution of entropy term to the micelle formation is superior to that of enthalpy term in the system under study, which indicates micellization is entropy driven. By comparing the cmc and ΔGmic it is evident that all cmc decreases and the more observed negative ΔGmic in the presence of different added salts. The anion effect on the guanidine surfactants micelle formation with added salts showed the micelle forming efficiency order as: Cl− < Br− < NO3− < Ac−.

Synthesis, Characterization and Surface Activity of Trioctyl Hydroxyethyl Ammonium Chloride

Abstract Trioctyl hydroxyethyl ammonium chloride was synthesized from trioctylamine, hydrochloric acid and ethylene oxide by a two-step process. The structure of the quaternary ammonium salt was characterized by FTIR and 1H NMR. The surface tension at the critical micelle concentration was measured to investigate the surface activity of it.