Bao-Lin Yin

Studies on the Physicochemical Properties of 3-Alkoxyl-2-hydroxypropyl Trimethylammonium Chloride–Sodium Dodecyl Sulfonate Binary-Surfactant Aqueous Systems

Surface tension, micelle formation, surface adsorption, and solubilization of dimethylaminoazobenzene (DMAB) are studied in aqueous solutions of 3-alkoxyl-2-hydroxypropyl trimethylammonium chloride (alkoxyl = CnH2n+1O, n = 8, 12, 14, 16), of sodium dodecyl sulfonate, and of mixtures of these cationic surfactants and the anionic surfactant at 40°C. Synergistic effects on micelle formation, surface tension reduction, and solubilization enhancement of DMAB are observed in the cationic–anionic mixed surfactant systems. The experimental results are discussed in the light of the interactions between the two kinds of surfactant ions.

1H NMR Study on Solubilization of Aromatic Solutes in Gemini Cationic Surfactant Micelles

The 1HNMR spectra of gemini cationic surfactant 1,3‐Propane diaminium N, N‐didodecyl‐2‐hydrxyl‐N,N,N′N′‐tetramethyl‐dichloride (ClC12H25‐(CH3)2N‐CH2CH(OH) CH2N(CH3)2 C12H25 Cl), abbreviated to GC12NCl solutions were determined in the presence of toluene, phenyl ethane, benzyl alcohol, or 2‐phenylethanol. Based on observations, probable solubilization sites of the substrate molecule within the micelles are discussed. The examined results indicate that the polarity of aromatic solutes affects their solubilization site in the micelle solution. The methylene in long chain of GC12NCl shows a single signal in the presence of toluene and phenyl ethane, however, when benzyl alcohol or 2‐phenylethanol is in existence, the peak of ethylenes in long chain Gemini surfactant splits into an upfield signal and a downfield signal in the solubilization system with enhancement of molar ratio of aromatic solutes to the sufactant. The addition of benzyl alcohol and 2‐phenylethanol causes a downfield shift of the methyl signal, the other signal were up field shifted by the addition of the phenyl derivatives. From the dependence of chemical shifts of GC12NCl on solubilizate concentration, it is ascertained that at low solubilizate contents the aromatic solutes are solubilized by adsorption at the micelle‐water interface. With further addition of aromatic solutes, the solubilization site of the solubilizate varied gradually from the mantle of the surfactant micelle to its inner core.

The Influences of Polymers and Temperature on the Foam Properties of 3‐Dodecylalkoxyl‐2‐hydroxylpropyl Trimethylammonium Chloride

The foam performances of 3‐dodecoxy‐2‐hydroxypropyl trimethylammonium chloride (C12TAC) have been determined in the existence of different relative amount of polymer. The experimental results show that the foaming ability of the mixture systems of the C12TAC/PEG and C12TAC/PVP is stronger than that of the surfactant solutions in the absence of polymer, and with the increase of relative amount of polymer both foaming efficiency and foam stability of the surfactant solutions are evidently enhanced. For the aqueous solution of the surfactant, effect of temperature on foaming properties has also been examined. The results show that both the foaming ability and stability of the foams of the surfactant solutions are highest (or strongest) at 30°C.

Thermodynamics of interaction between sodium dodecyl sulphate with 3-alkoxyl-2-hydroxypropyl trimethyl ammonium chlorides in aqueous systems

Interactions between sodium dodecyl sulphate (SDS) and four new surfactants, 3-alkoxyl-2-hydroxypropyl trimethyl ammonium chlorides (CnNCl) in aqueous systems were investigated using titration microcalorimetry. Pseudo-critical micellar concentration (pcmc), and thermodynamic parameters of the formation of mixed micelle for two binary surfactant systems at a certain concentration of CnNCl were estimated from the calorimetric data and the titration curve with methods from the literature. Changes in enthalpy and entropy of formation of the mixed micelle were discussed in the light of the structure of the surfactants and the iceberg model. The deduced conclusion is that interactions between hydrophobic chains of SDS and CnNCl are more important than the electrostatic attraction of the negatively charged head group of SDS with the positively charged head of CnNCl in the synergistic interaction between the anionic and cationic surfactants while the size of iceberg around the surfactant monomer is not sensitive to length of the hydrophobic chain.

Study on Surface Activity and Bacteriostasis of a Series of Gemini Cationic Surfactants

N, N′-didodecyl-2-hydrxyl-N, N, N′N′-tetramethyl-dichloride has been synthesized with R (CH3)2N (R = CnH2n+1, n = 12, 14, 16), hydrogen chloride and epoxy chloropropane as raw materials. The products have been characterized by element analysis and 1H NMR spectra. Fundamental interfacial behavior of the surfactant at the air/water interface has been investigated by means of surface tension measurements to provide an insight into relationship between the structure of the hydrophobic moiety and the surfactant properties. Foam performance and bacteriostasis in aqueous solution have been investigated. The results indicate that the gemini cationic surfactants have strong surface activity. The surface activity is relevant to the number of carbon atoms in the hydrophobic tail of surfactant molecule. The longer the alkyl chain is, the stronger the surface activity and the lower the critical micelle concentration will be. G12Cl2 solution possesses the best performance of the foaming ability and foam stability at 298.15 K, but bubbly and stability efficiency is the lowest among the three systems. Bacteriostasis of the surfactants has been determined with disk diffusion on filter paper. The results show that all of the newly synthesized double quaternary ammoniums possess quite good bacteriostasis.

Lyotropic Liquid Crystal Phases of the 3‐Heptaoxy‐2‐Hydroxypropyl Trimethyl Ammonium Bromide—n‐Butanol—Water System

Lyotropic liquid crystals formed in the ternary system of a novel cationic surfactant, 3‐heptaoxy‐2‐hydroxypropyl trimethyl ammonium bromide (R7TAB)—butanol—water system have been studied with particular emphasis on the specific regions in which either a single or coexisting liquid crystalline phases are observed. Colorized photographs showing characteristic texture structures of liquid crystalline phases have been obtained using polarizing‐light microscope. Small‐angle X‐ray scattering (SAXS), 2H (deuterium) quadrupolar splitting (2H NMR) were employed to confirm the microstructure of these liquid crystalline phases. The structural transformation of these lyotropic liquid crystals was also confirmed by differential scanning calorimetry (DSC).

Studies of Phase Behavior on R12TAB/Benzyl Alcohol/Water Ternary System

Phase behavior of ternary systems containing 3‐dodecyloxy‐2‐hydroxypropyl trimethyl ammonium bromide (R12TAB), benzyl alcohol and water have been studied at 25±0.1°C. Ternary phase diagram of the systems shows a clear, isotropic, and low‐viscous region, a L phase, two liquid crystalline phases (lamella and hexagonal liquid crystal), and a coexisted phase of the liquid crystalline and micelles. 2H nuclear magnetic resonance (2H NMR) technology and polarizing‐light microscope were employed to confirm the symmetry structure of the liquid crystals and the boundaries for the different phases. In L phase, three types of different micelle regions (reverse micelles, normal micelles, and bicontinuous structures zones) were confirmed by means of the electric conductivity and the proton nuclear magnetic resonance spectroscopy (1H NMR) measurements. The microcosmic structures of the micelle were investigated, and the solubilizing position of benzyl alcohol were located according to the chemical shift of protons.

Liquid Crystal and Rheological Behavior of 2,6-Bis(benzylidene)cyclohexanone

The liquid crystalline compound, 2,6-bis(benzylidene)cyclohexanone was synthesized using benzaldehyde and cyclohexanone as raw material, and tetrabutyl ammonium bromide as phase-transfer catalyst in the solution of sodium hydroxide. The effect of several factors, such as reaction time, reaction temperature, and concentration of sodium hydroxide, has been investigated. The product was characterized by infrared spectra, 1H NMR and elemental analysis. The physicochemical behavior of the crystalline compound was studied by differential scanning calorimetry, polarizing microscope, and rheometer. The experimental results show that the synthesized compound exhibits typical semectic thermot liquid crystal. Meanwhile, the crystal of the compound was determined by x-ray single crystal diffraction analysis. The crystal of the compound belongs to monoclinic system with space group P2(1)/c, a = 9.586(1) Å, b = 18.391(2) Å, c = 9.433(1)Å, α = 90°, β = 115.816(2)°, γ = 90°, Dc = 1.217 g · cm−3, V = 1496.9(3) Å−3, and Z = 4.