Mixed micellization and surface properties of non-ionic/cationic surfactants

We investigate the surface properties of aqueous binary mixtures of our cationic surfactant O-dodecyl-N,N′-diisopropylisourea hydrochloride (ISO-DIC C₁₂) with commercially available nonionic surfactant polyoxyethylene p-(1,1,3,3-tetramethylbutyl)phenyl ether (TritonX-100) at different temperatures (288 to 303?K). The micellization behavior of the binary systems is studied by determining the surface tension and other important physicochemical parameters, such as the critical micelle concentration (CMC), surface tension at the CMC(γ_cmc), Krafft Temperature (T_K), maximum excess concentration (Γ_max), minimum surface area per molecule (A_min), surface pressure at the CMC (П_cmc), and the adsorption efficiency (pC20) at the air/water interface. The study has additionally covered the calculation of thermodynamic parameters of micellization, including the standard Gibbs free energy, the standard enthalpy, the standard entropy, the free energy, and the Gibbs free energy of adsorption at air/water interface. The CMC values of the binary systems determined by experimental data are used to evaluate the micellar composition in the mixed micelle, the interaction parameter β and the activity coefficients f₁(ISO-DIC C₁₂) and f₂ (polyoxyethylene p-(1,1,3,3-tetramethylbutyl)phenyl ether) using the theoretical treatment proposed by Clint and Rubingh. Our results reveal that the proposed binary systems possess enhanced surface activity compared to those of the individual surfactants.     

Synthesis and solution properties of ionic liquid-type polysiloxane bola surfactants

Three novel ionic liquid (IL)-type polysiloxane bola surfactants (ATPS-MA, ATPS-EA, and ATPS-PA) were designed and synthesized using a two-step method. Their chemical structures were characterized by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (¹H NMR) spectroscopy. Their surface activity and aggregation behavior in aqueous solution were systematically investigated by surface tension measurements, transmission electron microscopy (TEM), and dynamic light scattering (DLS). Surface activity measurement results indicated that the γ_CMC of the three IL-type polysiloxane surfactants are under 25 mN m^?1, and much lower than those of conventional IL hydrocarbon bola surfactants due to the introduction of siloxane group at the end of the hydrophobic chains. TEM and DLS analyses results indicated that the three surfactants can self-assemble into spherical micelles with a range from 50 to 300?nm, indicating potential uses as model systems for biomembranes and vehicles for drug delivery.     

Effects of cationic head groups of ionic liquid on micellization in aqueous solution of PEO-PPO-PEO triblock copolymer

The interaction of ionic liquids (ILs) with non-ionic triblock copolymer, Pluronic® P123 in aqueous solutions has been investigated using DLS, surface tension, and viscosity measurements. The addition of ILs increased the Critical Micelle Concentration (CMC) of P123, which appears to be logistic. As the added IL enhances the solubility of PPO moiety (and PEO), which makes them to behave like a more hydrophilic block copolymer that would be micellized at high copolymer concentration. The DLS data is in good agreement to the results observed from surface tension measurements. Viscosity results show the propensity in micellar size reduction upon addition of ILs, and hence, intrinsic viscosity decreases as compared to pure P123 aqueous solution. The results are studied and discussed as a function of cationic head groups of N-octyl-pyridinium/imidazolium chloride based ILs.     

两性离子表面活性剂的合成及其表面性质

合成了一类含季铵基和磺酸基结构的非对称Gemini两性离子表面活性剂;利用红外光谱、质谱、离子定性试验验证了合成产物的分子结构,并测定了其表面性质.结果表明,目标产物的分子结构符合设计预期;五种非对称Gemini两性离子表面活性剂的表面张力在30mN/m左右,临界胶束浓度达到10-4~10-5数量级.此外,虽然非对称Gemini两性离子表面活性剂的起泡性能比相应单链型表面活性剂的稍差,但其稳泡性明显优于后者.     

Thin-layer chromatography in the analysis of surfactants: At a glance

This review presents the research work appeared in the literature during 1983–2016 on identification, separation, and determination of surfactants using different modes of thin-layer chromatography (TLC), e.g., normal phase TLC (NP-TLC), high-performance TLC (HP-TLC), and reversed-phase TLC (RP-TLC). The relative work done on these techniques follows the trend: NP-TLC?>?HP-TLC?>?RP-TLC. Most of the work performed has been concentrated on the analysis of nonionic surfactants compared to the other types of surfactants. The analysis trend of surfactants by TLC follows the order: nonionic?>?cationic?>?anionic?>?amphoteric. Green solvents as an eluant in TLC analysis of surfactants have been recently introduced. In addition, the entry of ionic liquids (ILs) as a mobile phase or as an impregnant of stationary phase tremendously increased the scope of TLC as green chromatographic technique in the analysis of surfactants. The advantageous features of ILs including negligible vapor pressure, good thermal stability, tunable viscosity, nonflammable, and miscibility with water and organic solvents as well as good extractability for various organic compounds and metal ions have expanded the scope of TLC in chemical analysis.     

磁性离子液体的应用研究

磁性离子液体是指能够吸附在磁铁上,在外加磁场作用下具有一定磁化强度的离子液体。本文综述了自2004年磁性离子液体概念提出至今在各领域的应用,其可以催化吡咯、3-甲基噻吩等单体合成导电高分子纳米微球,同时起到溶剂和模板的作用;还可以通过外加磁场调整产物的微观结构和形貌,从而得到不同的纳米结构;它也可以充当Lewis酸催化剂,催化傅克反应等一系列化学反应,并可以回收重复使用,而且回收有望通过磁场简单实现;与碳纳米管以共价键结合可以制备具有磁性的碳纳米管。除此之外,磁性离子液体在光控顺磁性超分子体系、吸收有机挥发物等领域的应用在近年也陆续有报道。     

Structure and properties of new ionic liquids based on alkyl- and alkenyltrifluoroborates.

A new series of low-melting, low-viscosity, hydrophilic ionic liquids, which comprise 1-ethyl-3-methylimidazolium ([EMI]+) and alkyl(alkenyl)trifluoroborate anions ([RBF3]-, R=n-C(m)H(2m+1) (m=1-5), CH2CH), were prepared and characterized. The phase-transition behavior, thermal stability, density, viscosity, conductivity, and surface tension of these salts were measured. The influence of the structural variations, such as changing the length and fluorination of the alkyl chain (R) in the anion [RBF3]-, on the above properties was extensively investigated. The low viscosity of these [RBF3]- salts suggests that a high degree of freedom and/or a somewhat flat-shaped feature in the anion make an important contribution to reducing the viscosity. The Walden products for each salt are not constant and vary with temperature, which suggests that the ions in these salts are not completely dissociated.     

Synthesis and properties of cationic surfactants with tuned hydrophylicity

A series of pyridinium-based cationic surfactants has been synthesised and their amphiphilic properties have been studied by conductivity and surface tension measurements. The modification of the substitution pattern on the pyridinium ring by hydrophobic moieties (methyl vs. hydrogen and presence or not of condensed benzene ring) gave the opportunity to investigate structure–activity relationships. Characterization by conductivity and surface tension measurements shed light on the behaviour at the air/water interface and in the micellar environment. In particular, the tendency to form ion pairs at very low concentration was evidenced for all the surfactants substituted on the ring, but not for the simple pyridinium ones. The formation of ion pairs affects both the conductivity and the surface tension plots, showing that a series of steps is involved during the adsorption to the air/water surface. An attempt was made to qualify the single steps in the adsorption at the surface layer. Those steps were attributed to different chemical species (free surfactant ions or ion pairs) and to different arrangements of the surfactant. This work also represents a contribution of investigation at very low surfactant concentrations and high surface tension values.     

Polymeric surfactants based on oleic acid. II. Copolymerization of sodium acrylamidostearate and 10-undecen-1-ol in a lamellar liquid crystal

Copolymerization of sodium acrylamidostearate (NaAAS) and 10-undecen-1-ol (UdOH) was performed in the lamellar liquid crystal (LLC) formed by NaAAS, UdOH, and water. After the polymerization the lamellar structure remained, and the disorder of the lamellar liquid crystal was, to some extent, reduced. Surface tension, small-angle X-ray diffraction, dynamic light scattering, viscosity, and fluorescence methods were used to study the properties of the copolymer. The polymeric surfactant behaves like polyelectrolyte and is more surface active than its precursor, i.e., NaAAS. The polymeric surfactant is capable of forming uni-molecular micelles through coiling of its hydrophobic chains. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2863–2872, 1999     

Newly designed polysiloxane-graft-poly (oxyethylene) copolymeric surfactants: preparation,surface activity and emulsification properties

Two sets of comb-grafted polymeric surfactants based on poly-(methylhydrogen siloxane) (PHMS) and/or poly(dimethylsiloxane) (PHMS-PDMS) were prepared by sililation of the active Si-H group with an active omega-vinyl group of specially designed undecenoic-polyethyleneglycol esters (UPEG) to form newly-designed polysiloxane-grafted-polyethyleneglycol comb-copolymeric surfactants.The hydrophilic moieties are hooked to the hydrophobic backbone through a spacer (undecenoic acid). The variations in the surfactants' structures were in the length and density of the grafted hydrophilic moieties, the chain length (DP) and nature of the hydrophobic backbone.The first 12 different polymeric surfactants (set 1), termed PHMS-UPEG, were found to be ineffective emulsifiers with limited ability to stabilize oil-in-water emulsions. The second set of surfactants, named PHMS-PDMS-UPEG comb-grafted copolymers, significantly reduced the oil-water interfacial tension and effectively stabilized several types of oil-in-water emulsions. The best emulsifier of this set (PHMS-PDMS-52-UPEG-45), seems to be the one whose anchor backbone (PHMS-PDMS) dissolves (rather than spreads) in the oil phase, and whose stabilizing moieties are sufficiently long (45 EO units) and hooked to the silicone backbone at high density (52% substitution).     

Surface activity and thermodynamic properties of water‐soluble polyester surfactants based on 1,3‐dicarboxymethoxybenzene used for enhanced oil recovery

The surface activity and thermodynamic properties for eight low molecular weight nonionic co‐polyester (PE) surfactants have been investigated. Surface and interfacial tensions (IFT) of surfactants in aqueous solutions were measured using the spinning drop technique. From these measurements, the critical micelle concentration (CMC), the surface pressure at CMC (Y_CMC), the maximum surface concentration (Γ_max), the minimum area/molecule at the aqueous solution/air interface (A_min), the effectiveness of surface tension reduction (Π_CMC), the alkane carbon number (n_min) and the IFT at n_min (Y_min) were determined. The thermodynamic parameters of micellization (ΔG_mic, ΔH_mic and ΔS_mic) and of adsorption (ΔG_ad, ΔH_ad and ΔS_ad) for these polymeric surfactants were also calculated. Structural effects on micellization and adsorption are discussed in terms of these parameters. The results show that the ΔG_ad values were more negative than ΔG_mic values for these compounds, so that they favored adsorption before the micellization process. They exhibited IFT in the order of 10⁻³ to 10⁻⁴ mN/m against the thin alkane carbon number range 6–9. This range seemed to be prefered for enhanced oil recovery. Copyright © 2000 John Wiley & Sons, Ltd.     

Aqueous immiscibility of cholinium chloride ionic liquid and Triton surfactants

The immiscibility windows of aqueous solutions containing the ionic liquid cholinium chloride (N_1112OHCl) and the non-ionic surfactants Triton X-100 and Triton X-102 have been determined by the cloud point method at temperatures ranging from T = (298.15 to 333.15) K. The experimental values have been correlated by using two well-known equations. The tie-lines have been ascertained by means of density and refractive indices measurement, and the experimental data have been modeled by the Othmer–Tobias, Bancroft and Setschenow equations. The use of cholinium chloride involves greater demixing capacity than other imidazolium-based ionic liquids.     

Mutual Influence of Some Flavonoids and Classical Nonionic Surfactants on Their Adsorption and Volumetric Properties at Different Temperatures

Due to the increasing practical use of mixtures of flavonoids with nonionic surfactants the presented studies were based on the measurements of surface tension and conductivity of aqueous solution of the quercetin (Q) and rutin (Ru) in the mixtures with Triton X-114 (TX114) and Tween 80 (T80) as well as the contact angle of model liquids on the PTFE surface covered by the quercetin and rutin layers. Based on the obtained results components and parameters of the quercetin and rutin surface tension were determined and the mutual influence of Q and Ru in the mixtures with TX114 and T80 on their adsorption and volumetric properties were considered. It was found, among others, that based on the surface tension isotherms of the aqueous solution of the single flavonoid and nonionic surfactant, the surface tension isotherms of the aqueous solution of their mixture, the composition of the mixed monolayer at the water-air interface as well as the CMC of flavonoid + nonionic surfactant mixture can be predicted. The standard Gibbs energy, enthalpy and entropy of the adsorption and aggregation of the studied mixtures were also found, showing the mechanism of the adsorption and aggregation processes of the flavonoid + nonionic surfactant mixture.     

Study on the Surface Property of Surfactant Ionic Liquids Solutions

The surfactant TX-100 can be dissolved in ionic liquid bmimPF6 and decrease the surface tension of 1-buty1-3-methylimidazolium hexafluorophosphate (bmimPF6) solutions. Here, we confirmed that in this new system, the pure solvents need rearrangement at the air-wate rinterface at the initial stage. The dynamic surface tension (DST) study shows that at the initial adsorption stage, the adsorption model of surfactant accords with the diffusion-controlled adsorption mechanism, and the dilute ionic liquids solutions is further close to the diffusion-controlled adsorption.     

Interfacial dilational properties of anionic gemini surfactants with polymethylene spacers

The dilational properties of anionic gemini surfactants alkanediyl-α,ω-bis(m-octylphenoxy sulfonate) (C₈C_mC₈) with polymethylene spacers at the water–air and water–decane interfaces were investigated by oscillating barriers and interfacial tension relaxation methods. The influences of oscillating frequency and bulk concentration on the dilational properties were explored. The experimental results show that the linking spacer plays an important role in the interfacial dilational properties. The moduli pass through one maximum for all three gemini surfactants at both water–air and water–decane interfaces. However, the values of moduli at the water–air interface are obviously higher than those at the water–decane interface because the sublayer formed by spacer chains will be destroyed by the insertion of oil molecules. Moreover, with the increase of spacer length, the surface adsorption film becomes more viscous at high concentration, which can be attributed to the process involving the formation of the sublayer. On the other hand, the spacers of the adsorbed C₈C₆C₈ molecules will extend into the oil phase when the interface is compressed. As a result, the interfacial film becomes more elastic with the increase of spacer length at high concentration. The experimental results obtained by the interfacial tension relaxation measurements are in accord with those obtained by the oscillating barriers method.     

Reduction of micellar size of PEO−PPO−PEO triblock copolymer in presence of ionic liquid in aqueous solutions: A SANS study

The interaction of ionic liquids (ILs) with non-ionic triblock copolymer, Pluronic® P123, in aqueous solutions has been investigated using Small Angle Neutron Scattering (SANS) measurements. The micellar structural parameters are obtained by fitting the SANS scattering data with model composed of core-shell form factor and a hard sphere structure factor of interaction, as a function of cationic head group of ILs. With the addition of ILs, a decrease in the micellar core, aggregation number, and hard sphere radius of P123 micelles was noticed. The results are discussed and explained as a function of cationic head groups of N-octylpyridinium/imidazolium chloride.     

Surface activities and thermodynamic properties of novel cationic surfactants with hydroxymethyl group

A new series of cationic surfactants, N–alkyl–N,N–dimethyl–N–(p–(hydroxymethyl) benzyl) ammonium chlorides (p-DHBA-m), were synthesized and the structures were characterized by ¹HNMR, ¹³CNMR, FT–IR and ESI–MS. The surface activities, thermodynamic properties and aggregation behaviors of p-DHBA-m in aqueous solutions were respectively studied by means of surface tension, isothermal titration calorimetry and steady-state fluorescence methods. Thermodynamic parameters show that the micellization is an entropy-driven process. According to the fluorescence quenching method, the micelle aggregation numbers (N_agg) of p-DHBA-m were calculated and found that the increase of temperature or the elongation of alkyl chain length could lead to the reduction of the N_agg, respectively.