Jia-Yong Yu

Dilational Viscoelasticity of the Zwitterionic Gemini Surfactants with Polyoxyethylene Spacers at the Interfaces

The dilational viscoelasticity of zwitterionic gemini surfactants C8ExNC12 with polyoxyethylene spacers at the water-air and water-decane interfaces were investigated by oscillating barriers method. The experiments were carried out at different concentrations with an accessible frequency range of 0.005 to 0.1 Hz. Interfacial tension relaxation method was employed to obtain dilational parameters in a reasonably broad frequency range. Experimental results show that the values of dilational elasticity and viscosity of C8ExNC12 are larger than those of common nonionic surfactants, such as T × 100, and the dilational viscoelasticity at the water-decane is close to that at the water-air interface on the whole. The results may be attributed to Coulombic attraction, and the possible schematic diagrams of adsorbed molecules with different polyoxyethylene spacers at the water-air and water-decane interfaces are proposed. We also analyzed C8ExNC12 from the results of relaxation experiments and Cole-Cole plots.

Study on Foaming Properties of Polyoxyethylene Alkyl Ether Carboxylic Salts with Different Structures

In this article, foaming properties, dynamic surface tension, and surface dilational properties were carried out with aqueous solutions of polyoxyethylene alkyl ether carboxylic salts to elucidate the relationship between foaming properties and surfactant structures. It was found that the dynamic surface tension of the solution is the key factor in determining the foamability: with increasing in the length of the hydrophobic group, dynamic surface activity becomes low, which leads to the low foam volume; the surfactant with branched-alkyl chain has faster diffusion rate, which lead to higher dynamic surface activity and higher foam volume. However, for straight chain surfactant, the foam stability is correlated with the surface dilational properties: the change rule of surface dilational modulus is consistent with that of the foam stability.

A Surface Rheological Study of Polyoxyethylene Alkyl Ether Carboxylic Salts and the Stability of Corresponding Foam

The dynamic dilational viscoelastic properties of polyoxyethylene alkyl ether carboxylic salts at the air-water interface were investigated by drop shape analysis method and their foam stability were measured by Bikerman Method. The influences of time, dilational frequency, and bulk concentration on surface dilational modulus and phase angle were expounded. The results show that the surfactant with the longest straight-chain shows the highest dilational modulus, which in agreement with the best foam stability. However, the foam stability of branched-alkyl chain surfactant cannot be explained in terms of film elasticity alone.

Interfacial Dilational Properties of Two Different Structure Demulsifiers at Oil–Water Interfaces

The dilational properties of demulsifiers PE1 and PE2 at the decane-water interface were investigated. Meanwhile, the influence of demulsifiers on interfacial dilational modulus of 5% crude oil also was explored. The experimental results indicate that the diffusion process is still not the main factors to control the properties of interfacial film even at large concentration. The dilational modulus of demulsifier PE2 passes through a maximum with the increasing concentration, and that of demulsifier PE1 changes a little with the increasing concentration at the decane-water interface. The dilational moduli of crude oil inerfaces decrease with the addition of both demulsifiers. At low concentration, the effect on reducing the dilational modulus of crude oil is stronger for PE1, which maybe caused by its higher substitution ability. For PE2, the ability to decrease interfacial dilational modulus gets stronger with increasing bulk concentration, which might be explained by that the adsorption increases with increasing concentration. The results of relaxation experiments support those obtain by oscillating barriers method.

Synthesis and Surface Activity of Anionic Gemini Surfactants with Alkyl Spacers

A series of anionic Gemini surfactants called alkanediyl-α,ω-bis(m-octylphenoxy sulfonate) with different length of (CH2)x spacer, C8CxC8 (x = 2, 4, 6, 8), have been synthesized from 4-n-octylphenol and their basic physicochemical properties are investigated. The results indicate that they are different from cationic Gemini surfactants called alkanediyl-α,ω-bis(dimethyldodecylammonium bromide), 12-(CH2)s-12, in the literature. It is found that as the carbon atom number of the spacer increases, the cmc (critical micelle concentration) decreases gradually, and the surface area per molecule (Amin) decreases initially and then increases. The breakpoints appear at number 4 of carbon atom in the spacer. Though the length of the spacer is different for the Gemini surfactants from C8C2C8 to C8C6C8, there is no obvious change on the micropolarity.

Adlayer structure of 4-ethyl naphthalene-1-sulfonate on Cu(111)

Abstract The adsorption of sodium 4-ethyl naphthalene-1-sulfonate has been studied by cyclic voltammetry and in situ scanning tunneling microscopy (STM). Electrochemical STM imaging reveals an ordered adlayer with a (4xa0×xa04) structure on Cu(1xa01xa01) in 0.1 M HClO4 in which the surfactant molecules are oriented parallel to the surface. The structural details of each molecule are well discerned. A structural model is proposed for the molecular arrangement.

Effect of alkyl chain length on the surface dilational rheological and foam properties of N -acyltaurate amphiphiles

The dynamic dilational properties of sodium 2-(2-(alkylaryloxy)-alkylamido)ethanesulfonates (12+nB-Ts) at the air–water interfaces were investigated by drop shape analysis, and their foam properties were also measured. The influences of time and bulk concentration on surface dilational properties were expounded. The results show that the molecular interaction controls the nature of adsorption film during lower concentration range, and the film behaves elastic in nature. During higher concentration range, the diffusion exchange process controls the dynamic dilational properties and the surface film shows remarkable viscoelasticity. An increase in hydrophobic chain length enhances the molecular interaction at low concentration and speeds up the diffusion exchange process at high concentration, which results in the different variations of modulus at different concentration regions. For 12+nB-Ts, too short a chain probably produces bad film elasticity, whereas too great a length produces too fast liquid drainage. Therefore the optimal length in the branched chain leads to the best foam stability.

Effect of Demulsifiers on Dilatational Properties of Crude Oil–Water Interfaces

The dilatational properties of polyether demulsifiers PEA, PEB, PEC, PED, PEF, and PEG at the decane-water interface were investigated. Meanwhile, the effect of demulsifiers with different structures on interfacial dilatational modulus of diluted crude oil also was explored. The properties of demulsifiers are compared and analyzed in combine with the dilatational parameters at decane-water interface and at 5% crude oil-water interface. The results show that interfacial dilatational viscoelasticity could characterize the interfacial behavior of demulsifiers. The demulsifiers, which have different kinds or structures, have different effects on destroying the interfacial film of crude oil with increasing bulk concentration. Therefore, the dosage of demulsifier is a very important role in controlling nature of crude oil film.

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.

Interfacial Dilational Properties of Acidic Model Oil and Chemical Flooding Systems

The interfacial dilational properties of lauric acid model oil and chemical flooding systems have been investigated by means of longitudinal method. The influences of acid on the dilational viscoelasticity of partly hydrolyzed polyacrylamide (HPAM) and anionic surfactants (4,5-diheptyl-2-propylbenzene sulfonate 377 and Gemini surfactant C12COONa-p-C9SO3Na) have been expounded. The results show that lauric acid concentration is an important factor in controlling the dilational properties of mixed-adsorption layer. The addition of small amounts of lauric acid to solutions of anionic surfactant appears to increase the dilational modulus, while the superfluous addition could decrease the dilational modulus mainly due to the weakening of strong interaction among long alkyl chains of surfactant molecules. The polymer plays different roles in influencing the nature of adsorbed layers at different lauric acid concentrations: at low concentration, the addition of polymer perhaps weakens the hydrophobic interactions of lauric acid molecules, which results in decreasing the dilational modulus of adsorbed layer. At high concentration, the addition of the polymer increases the dilational modulus due to hydrophobic interactions between polymer and lauric acid molecules. At the same time, the mixed adsorbed layer shows low frequency due to the slow diffusivity of polymer molecules. The addition of lauric acid to polymer-surfactant system will further increases diffusion-exchange process between the interface and the bulk, which consequently leads to the decrease in dilational modulus.