Zhiqiang Jin

Synthesis and Properties of Anionic Surfactants Containing Oxyethylene Group or/and Branched Tail

Using Guerbet tetradecyl alcohol C14GA (synthesized by Guerbet reaction using 1-heptanol as raw material) as intermediate, sodium Guerbet tetradecyl polyoxyethylene ether sulfates [C14GA(EO)nS, n = 1, 2, 4] were obtained through following steps: synthesizing Guerbet tetradecyl polyoxyethylene ether alcohols [C14GA(EO)nH, n = 1, 2, 4] by Williamson reaction, then esterifying with chlorosulfonic acid so as to form Guerbet tetradecyl polyoxyethylene ether alcohol sulfates [C14GA(EO)nSO3H, n = 1, 2, 4], and finally neutralizing with sodium hydroxide; while sodium Guerbet tetradecyl sulfate(C14GAS) was synthesized only through esterifying and neutralizing reactions. The structures of these anionic surfactants were determined by infrared, nuclear magnetic resonance, and element analysis. The surface activity of these surfactants was studied by means of surface tension. The results have shown that these surfactants possess higher surface activity than the common surfactant C12H25OSO3Na. Branched-tail structure coming from Guerbet alcohol makes the anionic surfactant (C14GAS) have higher critical micelle concentration (CMC) and better effectiveness in lowering the interface tension between air and water than their linear counterpart (C14H29OSO3Na). Introducing oxyethyene group into the place between head group and tail group of the surfactant molecule with branched tail can lower the CMC, γcmc, and Krafft point. And the effectiveness for reducing the CMC, γcmc, Γmax, and Krafft point of surfactant increased with the increase of oxyethylene group number (n = 1, 2, 4). The relationship between the molecular structure and surface activity of surfactant is discussed.

Dilational rheological properites of oxyethylated fatty acid methyl esters at kerosene-water interface

Abstract Dilational rheological properties of oxyethylated fatty acid methyl esters (FMEEs) with different structure (C12E5、C14E5、C16E5 and C18=E5) at kerosene-water interface have been investigated as a function of time, frequency and bulk concentration by the oscillating drop method. The experimental results show that the dilational modulus increases with an increase in the alkyl chain length for FMEEs with saturated alkyl chains (C12E5、C14E5 and C16E5) due to the enhanced hydrophobic interaction among the molecules at interface and the slowed diffusion-exchange process. At the same time, the phase angles are relative low, which embodies characteristics of nonionic surfactants containing EO chain. As for C18=E5, the introduction of a double bone causes a decrease in the dilational modulus and a slight increase in the phase angle, as evidenced by an increase in the value of the slope of curve, because the flexible unsaturated alkyl chain enhances the diffusion-exchange process. Moreover, the modulus vs interfacial pressure curve passes through a maximum during higher interfacial pressure range for C18=E5, which indicates that the interfacial rearrangement process affects the nature of adsorption layer. Graphical Abstract