Lower CMC Values Research Articles

Self–aggregation Behavior of Dialkyl Imidazolium based Ionic Liquids in Aqueous Medium: Effect of Alkyl Chain Length

AbstractA series of new dialkyl imidazolium based ILs viz. N‐butyl‐N‐alkylimidazolium bromides, [CmCnmim][Br], where m=4, n=4, 8 and 12 have been synthesized, characterized and investigated for their self‐aggregation behavior in aqueous medium. Various techniques such as tensiometry, steady state fluorescence, isothermal titration calorimetry (ITC), dynamic light scattering (DLS), transmission electron microscopy (TEM) and 1H nuclear magnetic resonance (NMR) have been employed to get detailed information about the self‐aggregation phenomenon. The investigated ILs have shown better adsorption and micellization behavior in comparison to single chain imidazolium based ILs in terms of higher adsorption efficiency and lower cmc values. TEM measurements provided insights into morphology of aggregates where spherical micelles and doughnut shaped vesicle like structures have been observed depending on the molecular structure of IL. The structure of aggregates formed by these ILs at molecular level has been proposed by analyzing the change in chemical shifts of various protons of ILs upon micellization along with information obtained from other techniques.

Modulated cellular delivery of anti-VEGF siRNA (bevasiranib) by incorporating supramolecular assemblies of hydrophobically modified polyamidoamine dendrimer in stealth liposomes

A novel lipopolymer based system was designed and characterized for cellular delivery of anti-VEGF siRNA in SKBR-3 breast tumor cell line. Polyamidoamine (PAMAM) dendrimers of low generations (G1, G2 and G3) were incorporated into polyethylene glycol (PEG)-stabilized liposomes by following the consecutive steps: (a) synthesis of the cholesterol conjugates (40% molar ratio of cholesterol to primary amines of PAMAM), (b) incorporation of the conjugates in liposome by lipid mixing and (c) microencapsulation of the siRNA using the ethanol drop method. The cholesterol conjugates of PAMAM dendrimers (G1-Chol40%, G2-Chol40% and G3-Chol40%) formed self assembly with low CMC values (<11μg/ml). Not only did G2-Chol40% show the highest lipid mixing among the cholesterol conjugates, but also, had the lowest leakage of encapsulated carboxyfluorescein tracer. Various N(amine))/L(lipid)/P(phosphate) mole ratios were investigated for siRNA condensation by ethidium bromide dye exclusion assay. The optimum N/L/P ratio of 20:33:10 was chosen for microencapsulation of anti-VEGF siRNA by ethanol drop method, showing particle size of 130nm, zeta-potential of +4mV, siRNA loading efficiency and capacity of 96% and 13wt%, and high stability against heparin sulfate (extracellular matrix). TEM shows uniform and discrete oligo- or multi-lamellar vesicular structures. The liposome incorporating G2-Chol40% was successfully internalized into SKBR-3 cells mainly through clathrin-mediated endocytosis, which was able to escape from endosomes and showed a significantly higher sequence-specific inhibition of VEGF expression and cell growth than the respective G2-Chol40%/siRNA dendriplexes. Importantly, the cytotoxicity decreased with incorporation of G2-Chol40% in the liposomes.

Surface and Antimicrobial Activity of Sulfobetaines

AbstractSulfobetaines belong to the group of zwitterionic surfactants. They are electroneutral salts, which have in the same molecule, two ionic centers with different charge. Due to the specific structure they exhibit excellent properties such as good solubility in water and detergency. In this paper we present surface properties and adsorption parameters of sulfobetaines in water/air systems. From the adsorption isotherms the CMC value, the surface tension and surface pressure at the CMC as well as the efficiency of adsorption were determined. Physicochemical analyses of the data allowed for the further description of adsorption process. Results showed that sulfobetaines exhibit good surface properties especially low CMC and p20 values. Additionally the antimicrobial activity of sulfobetaines solutions against gram‐positive and gram‐negative bacteria were tested by the well‐diffusion method. MIC values and growth kinetics were determined by microdilution method. Antimicrobial assays demonstrated that sulfobetaines can be good antibacterial agents, but the activity of surfactants strongly depends on alkyl chain length.

Coordinated pH/redox dual-sensitive and hepatoma-targeted multifunctional polymeric micelle system for stimuli-triggered doxorubicin release: Synthesis, characterization and in vitro evaluation

Multifunctional polymeric micelles self-assembled from a DOX-conjugated methoxypolyethylene glycols-b-poly (6-O-methacryloyl-d-galactopyranose)-disulfide bond-DOX (mPEG-b-PMAGP-SS-DOX) copolymer were prepared as an antitumor carrier for doxorubicin delivery, of which the chemical modification with disulfide bonds and hydrazone bonds allowed micelles to release doxorubicin (DOX) selectively at acidic pH and high redox conditions. The resulting micelles exhibited coordinated pH/redox dual-sensitive and hepatoma-targeted multifunction with sustaining stability in aqueous media. The multifunctional micelles showed spherical shapes with a mean diameter of 93±2.08nm, a low polydispersity index (PDI) of 0.21, a low CMC value of 0.095mg/mL, a high drug grafting degree of 56.9% and a drug content of 39.0%. Remarkably, in vitro drug release studies clearly exhibited a pH and redox dual-sensitive drug release profile with significantly accelerated drug release treated with pH 5.0 and 10mM GSH (88.4% in 72h) without drug burst release. The tumor proliferation assays indicated that DOX-grafted micelles, along with low cytotoxicity and well biocompatibility to normal cells up to a concentration of 10μg/mL, inhibited the proliferation of HepG2 cells in a formulation-, time- and concentration-dependent manner in comparison with MCF-7 cells which was similar to free DOX. Anticancer activity releaved that the disulfide-modified micelles possessed much higher anti-hepatoma activity with a low IC50 value of 1.1μg/mL following a 72h incubation. Furthermore, the intracellular uptake tested by CLSM and FCM demonstrated that multifunctional polymeric micelles could be more efficiently taken up by HepG2 cells compared with MCF-7 cells, agreed well with MTT assays, suggesting these well-defined micelles provide a potential drug delivery system for dual-responsive controlled drug release and enhanced anti-hepatoma therapy.

Commentary: Oil degradation and biosurfactant production by the deep sea bacterium Dietzia maris As-13-3.

Commentary: Oil degradation and biosurfactant production by the deep sea bacterium Dietzia maris As-13-3.

Syntheses of cardanol-based cationic surfactants and their use in emulsion polymerisation

AbstractSix quaternary ammonium salts were designed and synthesised with moderate to high yields in three steps, based on cardanol, a low-cost and abundant renewable resource. The new ammonium salts can act as reactive surfactants due to their having both a hydrophilic ammonium group and a hydrophobic unsaturated alkyl chain. The gemini surfactants with a linker of a linear saturated aliphatic hydrocarbon chain exhibited a relatively low CMC value(≤ 0.2 mmol L

Enzymatic PEGylated Poly(lactone-co-β-amino ester) Nanoparticles as Biodegradable, Biocompatible and Stable Vectors for Gene Delivery.

We have developed new, efficient gene delivery systems based on PEGylated poly(lactone-co-β-amino ester) block copolymers that are biodegradable, stable and low in toxicity. The PEG-poly[PDL-co-3-(4-(methylene)piperidin-1-yl)propanoate] (PEG-PPM) diblock and PPM-PEG-PPM triblock copolymers with various compositions were synthesized in one step via lipase-catalyzed copolymerization of ω-pentadecalactone (PDL) and ethyl 3-(4-(hydroxymethyl)piperidin-1-yl)propanoate (EHMPP) with an appropriate PEG (MeO-PEG-OH or HO-PEG-OH). The amphiphilic block copolymers are capable of condensing DNA in aqueous medium via a self-assembly process to form polyplex micelle nanoparticles with desirable particle sizes (70-140 nm). These micelles possess low CMC values and are stable in the medium containing serum protein molecules (FBS). Among the PEG-PPM and PPM-PEG-PPM micelles, the PEG-PPM-15% PDL micelle particles exhibited high DNA-binding ability, the fastest cellular uptake rate and highest gene transfection efficacy. Flow cytometry analysis shows that LucDNA/PEG-PPM-15% PDL polyplex micelles can effectively escape from endosomal degradation after cellular uptake likely due to the presence of the tertiary amine groups in the copolymer chains that act as proton sponges. In vitro cytotoxicity and hemolysis assay experiments indicate that all copolymer samples are nonhemolytic and have minimal toxicity toward COS-7 cells within the polymer concentration range (≤200 μg/mL) used for the gene transfection. These results demonstrate that the PEGylated poly(lactone-co-β-amino ester) block copolymers are promising new vectors for gene delivery applications.

One-pot synthesis of crosslinked amphiphilic polycarbonates as stable but reduction-sensitive carriers for doxorubicin delivery

In this paper, we first synthesized a novel disulfide-coupled bis-(cyclic carbonate) (TDCSS) monomer. After ring-opening co-polymerization (ROP) of TDCSS and trimethylene carbonate (TMC) initiated by mono-methoxyl poly(ethylene glycol), the crosslinked reduction-sensitive copolymer PEG-P(TMC-co-TDCSS) was obtained via a facile one-step procedure for efficient delivery of doxorubicin (DOX) into cancer cells. To serve as controls, PEG-P(TMC-co-TDCCC), which has an analogous structure without disulfide bond, and a linear polymer PEG-PTMC were also prepared. The copolymers could self-assemble to form nano-sized micelles in an aqueous solution. As compared to PEG-PTMC, crosslinked PEG-P(TMC-co-TDCSS) and PEG-P(TMC-co-TDCCC) showed lower CMC values and thus induced a much better micelle-forming ability. In vitro release studies revealed that the drug release behavior of DOX-loaded PEG-P(TMC-co-TDCSS) micelles, which could be accelerated in the presence of 10 mM dithiothreitol (DTT), showed a similar trend in the absence of DTT compared to DOX-loaded PEG-P(TMC-co-TDCCC) micelles. Furthermore, confocal laser scanning microscopy (CLSM) indicated that DOX-loaded PEG-P(TMC-co-TDCSS) micelles were efficiently internalized into HeLa cells, releasing DOX into the cytoplasm after which the drug finally entered the nuclei, while MTT assays also demonstrated potent cytotoxic activity against HeLa cells. DOX was mainly located in the cytoplasm for reduction-insensitive PEG-P(TMC-co-TDCCC) and PEG-PTMC controls.

Micellization and Synergistic Effect in an Aqueous Solution of an AOS-TX100 Mixture: Before and After Equilibrium in the Presence of Clay

In this research, a novel surfactant mixture consisting of anionic (alpha olefin sulfonate [AOS]) and nonionic (TX100) type was developed. Possible synergistic effect in micelle formation in different mass ratios of the mixture (1:2, 1:1, and 2:1) was studied by surface tension measurement method. Rubingh's Regular Solution theory was used to evaluate the interaction parameters (β) and activity coefficient (f) for both binary mixture and single surfactants, before and after equilibrium in the presence of clay minerals (kaolinite and illite). The differences between experimentally obtained CMC values and ideally calculated values, showed nonideality of the mixtures. In addition, the lower CMC values of mixtures in comparison with individual surfactants were an indication of synergism. The synergistic effect was maintained before and after equilibrium with clay minerals. The β values of the mixture before equilibrium were in the range –1.5 to –2.6. However, after equilibrium with kaolinite, the values were in the range of –1.9 to –3.9 while after equilibrium with illite they were in the range –1 to –3. For the mixture, before and after equilibrium, the synergism became more severe as mole fractions of AOS increased in the mixture.

Experimental and Theoretical Approach to Mixed Systems of Non-Ionic Cremophor EL and Cationic Gemini Surfactants in Aqueous Solution

Abstract Surfactant solutions in practical applications usually are mixtures of different types, especially ionic and nonionic ones. The mixing behavior of nonionic Cremophor EL-cationic gemini systems was therefore investigated by surface tension measurements. The Gemini surfactants used were of the type alkanediyl – α, ω – bis(dimethylalkylammonium bromide), (alkyl: 14 or 16 and alkane: butane, pentane or hexane), designated in the text as 14-s-14/16-s-16 (where s is the spacer length). The experimental results indicated that the mixed systems of EL with 16-6-16, 14-5-14 and 14-6-14 have lower cmc values than of pure surfactants. Comparison between experimental and calculated values of cmc (cmc and cmcid) showed that the interaction between the component amphiphiles inside aggregates of EL with RH, 16-4-16, 16-5-16 and 14-4-14 was not ideal but shows antagonism. Such fact was reflected by the values of activity coefficients also. This may be due to the steric repulsions which decrease with the increase in spacer length. The aggregates were mainly comprised of geminis at low stoichiometric mole fraction of EL (α 1) while by EL at high α 1. The molecular interaction parameter, β m, calculated using Rubingh's approach, was negative for mixed systems of EL with 16-6-16, 14-5-14 and 14-6-14. Surface parameters, evaluated by Rosen's model, also suggested mixed monolayer formation with negative β σ for all 16-s-16, 14-4-14 and 14-6-14 systems.

Solubility enhancement of anthracene and pyrene in the mixtures of a cleavable cationic gemini surfactant with conventional surfactants of different polarities

Schematic representation for solubilization of the PAHs in mixed micelles of ester-linked cationic gemini with conventional surfactants. • An ester-containing gemini surfactant of lower toxicity was used for the study. • Interaction of 12-E2-12 with erythrocytes shows less toxicity than other surfactants. • PAHs solubilization performed in equimolar gemini-conventional surfactant mixtures. • Aqueous solubility of PAHs is increased for all the pure/mixed surfactant systems. • Solubility enhancement of pyrene is higher than anthracene. In this study, the solubilization of anthracene and pyrene was investigated in micellar solutions of ethane-1,2-diyl bis( N , N -dimethyl- N -dodecylammoniumacetoxy) dichloride (C 12 H 25 (CH 3 ) 2 N + (CH 2 COOCH 2 ) 2 N + (CH 3 ) 2 C 12 H 25 ·2Cl − , 12-E2-12) and its equimolar binary mixtures of conventional cationic, anionic and nonionic surfactants in water. Critical micelle concentration ( cmc ) and other physicochemical parameters were determined by the surface tension and conductivity measurements at 30 °C. Much lower cmc value was obtained for 12-E2-12 than the corresponding monomeric surfactant dodecyltrimethylammonium chloride (DTAC). Lower experimental cmc than the ideal cmc and the negative interaction parameters imply synergistic interaction between the surfactants in the binary solutions. Order of solubilization capacity of the pure/mixed surfactant micelles, for anthracene and pyrene, are not the same. Among the pure surfactants, Brij 58 has highest and SDBS has least efficiency for dissolution of the solutes. The mixed systems 12-E2-12 + SDS and 12-E2-12 + Brij 58 have highest dissolution power for anthracene and pyrene, respectively. Solubility enhancement was observed for both the solutes in the equivalent binary mixtures of the dicationic gemini 12-E2-12 with the anionic conventional surfactants SDS and SDBS. To determine the toxicity of 12-E2-12 and to quantify its interaction with erythrocytes, we have performed the hemolytic assessment. As regards the hemolytic activity and biodegradability test, 12-E2-12 is less toxic and readily biodegradable.

Valorization of tannery wastes: Lipoamino acid surfactant mixtures from the protein fraction of process wastewater

Abstract The first stages of the transformation process of hides into leather (beamhouse process) generate an important waste in the tanning industry, since a considerable fraction of solubilized proteins ends up in waste water with the corresponding increase in contamination parameters, especially when the process is carried out without hair recovery (hair-pulping process). The objective of this work was the valorisation of this waste (the separated protein fraction) which conveniently hydrolyzed to amino acid level constituted the starting material for the production of biodegradable surfactants. The lipoamino acid surfactants were obtained by acylation of the amino acids from the protein hydrolysate. These surfactants were characterized and their physico-chemical and biological properties evaluated. They exhibit very low cmc values (about 40 mg/L). These surfactants are readily biodegradable and present an aquatic toxicity significantly lower than many common commercial surfactants derived whether from renewable or petrochemical feedstock. The mixtures of surfactants obtained are able to form oil/water emulsions that remain stable for at least 1 year. The results obtained in this work confirmed that it is possible the production of biodegradable and efficient lipoamino acid surfactant mixtures from the protein fraction present in beamhouse process wastewaters. This study constitutes a promising approach for the reduction of the pollution load from industrial tannery wastes and its valorisation as raw material for the production of surfactants with excellent environmental properties and good technical properties.

Self-assembly and antimicrobial activity of long-chain amide-functionalized ionic liquids in aqueous solution

Surface active amide-functionalized ionic liquids (ILs) consisting of a long alkyl chain (C6C14) connected to a polar head group (methylimidazolium or pyridinium cation) via an amide functional group were synthesized and their thermal stability, micellar properties and antimicrobial activity in aqueous solution investigated. The incorporation of an amide group increased the thermal stability of the functionalized ionic liquids compared to simple alkyl chain substituted ionic liquids. The surface activity and aggregation behaviour in aqueous solution of amide-functionalized ionic liquids were examined by tensiometry, conductivity and spectrofluorimetry. Amide-functionalized ILs displayed surface activity and their critical micelle concentration (cmc) in aqueous media decreased with the elongation of the alkyl side chain as occurs for typical surfactants. Compared to non-functionalized ILs bearing the same alkyl chain, ionic liquids with an amide moiety possess higher surface activity (pC20) and lower cmc values. The introduction of an amide group in the hydrophobic chain close to the polar head enhances adsorption at the air/water interface and micellization which could be attributed to the H-bonding in the headgroup region. The antimicrobial activity was evaluated against a panel of representative Gram-negative and Gram-positive bacteria and fungi. Amide-functionalized ILs with more than eight carbon atoms in the side chain showed broad antimicrobial activity. Antibacterial activities were found to increase with the alkyl chain length being the C12 homologous the most effective antimicrobial agents. The introduction of an amide group enhanced significantly the antifungal activity as compared to non-functionalized ILs.

Fmoc-conjugated PEG-vitamin E2 micelles for tumor-targeted delivery of paclitaxel: enhanced drug-carrier interaction and loading capacity.

The purpose of this study is to develop an improved drug delivery system for enhanced paclitaxel (PTX) loading capacity and formulation stability based on PEG5K-(vitamin E)2 (PEG5K-VE2) system. PEG5K-(fluorenylmethoxycarbonyl)-(vitamin E)2 (PEG5K-FVE2) was synthesized using lysine as the scaffold. PTX-loaded PEG5K-FVE2 micelles were prepared and characterized. Fluorescence intensity of Fmoc in the micelles was measured as an indicator of drug-carrier interaction. Cytotoxicity of the micelle formulations was tested on various tumor cell lines. The therapeutic efficacy and toxicity of PTX-loaded micelles were investigated using a syngeneic mouse model of breast cancer (4T1.2). Our data suggest that the PEG5K-FVE2 micelles have a low CMC value of 4μg/mL and small sizes (~60nm). The PTX loading capacity of PEG5K-FVE2 micelles was much higher than that of PEG5K-VE2 micelles. The Fmoc/PTX physical interaction was clearly demonstrated by a fluorescence quenching assay. PTX-loaded PEG5K-FVE2 micelles exerted more potent cytotoxicity than free PTX or Taxol formulation in vitro. Finally, intravenous injection of PTX-loaded PEG5K-FVE2 micelles showed superior anticancer activity compared with PEG5K-VE2 formulation with minimal toxicity in a mouse model of breast cancer. In summary, incorporation of a drug-interactive motif (Fmoc) into PEG5K-VE2 micelles represents an effective strategy to improve the micelle formulation for the delivery of PTX.

The self-assembly properties of a series of polymerizable cationic gemini surfactants: Effect of the acryloxyl group

A new series of polymerizable cationic gemini surfactants bearing acryloxyl group in spacer and a variable alkyl chain length were synthesized and their surface active properties alongside with their self-assembly properties were investigated by surface tension measurement, electrical conductivity, fluorescence and dynamic light scattering (DLS) measurements. As compared to single-chain surfmer, this study shows that the gemini surfmers possess low critical micellar concentration (cmc) value and the surface tension value at cmc (γcmc). While compared to corresponding gemini surfactant without acryloxyl group, the introduction of the acryloxyl group into spacer results in a lower cmc value, higher degree of ionization and micropolarity of aggregate. The aggregates with large hydrodynamicradius (Rh) of 70–110nm as the main component were observed in the surfmer solution, while the size of aggregate constructed by corresponding gemini surfactant without acryloxyl group is far smaller than the former. All the results can be attributed to the existence of intramolecular dipolar interaction between the carbonyl of acryloxyl group and the cationic nitrogen atom. This increases the hydrophobicity and the regularity of the molecule, which induces the formation of tighter and larger size aggregate in comparison with corresponding gemini without the acryloxyl group on the spacer.

Self-assembly, DNA binding and cytotoxicity trends of ether functionalized gemini pyridinium amphiphiles

Six new ether functionalized gemini pyridinium amphiphiles have been synthesized having dodecyl, tetradecyl alkyl chain lengths and three different spacers (i.e. –(CH2)n–, where n is 4, 5 and 6) and investigated for their self-assembling behavior by state of the art techniques such as tensiometry, conductivity and spectrofluorometry. These new pyridinium gemini surfactants exhibit lower cmc values as compared to other gemini surfactants reported in literature. These amphiphiles form stable complexes with DNA as established by agarose gel electrophoresis and ethidium bromide exclusion experiments. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was carried out in vitro on C6 glioma cell line for cytotoxicity assessment of new pyridinium geminis. The dynamic light scattering (DLS) and transmission electron microscopy (TEM) have been used to measure the micellar size of gemini surfactants. Further, thermal stability of these amphiphiles has been evaluated by thermogravimetric analysis (TGA). The dependence of self-assembly behavior and other properties on spacer as well as alkyl chain length has been established.

A New Type of Surfactant in the Synthesis and Performance Evaluation

Gemini surfactants are chemical compounds known as new generation of surfactants that their molecules has two hydrophilic groups ,two hydrophobic groups and a spacer.They have low CMC value and high surface activity.Gemini surfactants are inapproachable by any surfactants that are used for TOR nowadays.This essay is meant to solve the problems faced in the territory by using the remarkably high surface activity,introducing Gemini surfactants to TOR and launch series of experiments.Meanwhile,it provides technical and theoretical support for applying Gemini surfactants into the field.

Design and Characterization of PEG-Derivatized Vitamin E as a Nanomicellar Formulation for Delivery of Paclitaxel

Various PEG-Vitamin E conjugates including d-α-tocopheryl poly(ethylene glycol) succinate 1000 (TPGS) have been extensively studied as a nonionic surfactant in various drug delivery systems. However, limited information is available about the structure-activity relationship of PEG-Vitamin E conjugates as a micellar formulation for paclitaxel (PTX). In this study, four PEG-Vitamin E conjugates were developed that vary in the molecular weight of PEG (PEG2K vs PEG5K) and the molar ratio of PEG/Vitamin E (1/1 vs 1/2) in the conjugates. These conjugates were systematically characterized with respect to CMC, PTX loading efficiency, stability, and their efficiency in delivery of PTX to tumor cells in vitro and in vivo. Our data show that PEG5K-conjugates have lower CMC values and are more effective in PTX loading with respect to both loading capacity and stability. The conjugates with two Vitamin E molecules also worked better than the conjugates with one molecule of Vitamin E, particularly for PEG2K-system. Furthermore, all of the PEG-Vitamin E conjugates can induce significant suppression of P-gp function. More importantly, PTX-loaded PEG5K-VE2 resulted in significantly improved tumor growth inhibitory effect in comparison to PTX formulated in PEG2K-VE or PEG2K-VE2, as well as Cremophor EL (Taxol) in a syngeneic mouse model of breast cancer (4T1.2). Our study suggests that PEG5K-Vitmin E2 may hold promise as an improved micellar formulation for in vivo delivery of anticancer agents such as PTX.

Cholesterol Monohydrate Dissolution in the Presence of Bile Acid Salts

The molecular-level dissolution of cholesterol monohydrate single crystal (001) surfaces was systematically investigated in aqueous solutions of chenodeoxycholate (CDC) and ursodeoxycholate (UDC) using in situ atomic force microscopy (AFM). Dissolution via the layer-by-layer step retreat of monolayers was observed in solutions where the bile salt concentration exceeded the critical micelle concentration (cmc). Studies performed in CDC solution revealed markedly lower cmc values than in UDC. An abrupt transition from sporadic to continuous dissolution between ∼4–7 mM CDC was consistent with a previously proposed 2-step model for micelle formation. In contrast, cholesterol dissolution in UDC was apparent at ∼14 mM with no abrupt change in dissolution rate with increasing UDC concentration. Comparison with previous dissolution studies performed in aqueous ethanol (Cryst. Growth Des. 2005, 5, 2146–2153) reveal key differences in micelle-mediated versus bulk dissolution mechanisms.

Interaction between Zwitterionic Surface Activity Ionic Liquid and Anionic Surfactant: Na+-Driven Wormlike Micelles

The physicochemical properties of the mixed zwitterionic surface activity ionic liquid/anionic surfactant (N-alkyl-N'-carboxymethyl imidazolium inner salts/sodium dodecyl sulfate, [N-C(12), N'-CO(2)-Im]/SDS) at various molar ratios (R(1) = C([N-C(12),N'-CO(2)-Im])/(C([N-C(12),N'-CO(2)-Im]) + C(SDS)) were investigated by surface tension and steady-state fluorescence measurements. The results show that the mixed [N-C(12), N'-CO(2)-Im]/SDS system has a much lower cmc value and higher surface activity than individual surfactant. Compared with the mixed zwitterionic betaine surfactant/SDS system, the mixture studied exhibits a stronger synergism, i.e., more negative interaction parameters (β(m) and β(σ)). Through addition of NaCl, the wormlike micelles (WMs) could be formed in a [N-C(12), N'-CO(2)-Im]/SDS system. Steady and dynamic rheology was employed to characterize the WMs with different surfactant ratio (R(1)), NaCl concentration, and temperature. An optimal composition, viz., C(T) = 60 mM, R(1) = 0.45, and C(NaCl) = 0.10 M, was detected to form the strongest and longest wormlike micelles. Compared with the WMs formed by a traditional zwitterionic C(12) betaine/anionic surfactant mixture (e.g., laurylamidopropyl betaine/SDS), the WMs studied have a stronger network structure, which is expected to have potential applications in some fields, such as in nanomaterials synthesis, personal care products, and flooding liquid for tertiary oil recovery.