Lifei Zhi

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.