Surface Tension Techniques Research Articles

Development of Cholinium-Based API Ionic Liquids with Enhanced Drug Solubility: Biological Evaluation and Interfacial Properties.

We report an efficient sustainable two-step anion exchange synthetic procedure for the preparation of choline API ionic liquids (Cho-API-ILs) that contain active pharmaceutical ingredients (APIs) as anions combined with choline-based cations. We have evaluated the in vitro cytotoxicity for the synthesized compounds using three different cells lines, namely, HEK293 (normal kidney cell line), SW480, and HCT 116 (colon carcinoma cells). The solubility of APIs and Cho-API-ILs was evaluated in water/buffer solutions and was found higher for Cho-API-ILs. Further, we have investigated the antimicrobial potential of the pure APIs, ILs, and Cho-API-ILs against clinically relevant microorganisms, and the results demonstrated the promise of Cho-API-ILs as potent antimicrobial agents to treat bacterial infections. Moreover, the aggregation and adsorption properties of the Cho-API-ILs were observed by using a surface tension technique. The aggregation behavior of these Cho-API-ILs was further supported by conductivity and pyrene probe fluorescence. The thermodynamics of aggregation for Cho-API-ILs has been assessed from the temperature dependence of surface tension. The micellar size and their stability have been studied by dynamic light scattering, transmission electron microscopy, and zeta potential. Therefore, the duality in the nature of Cho-API-ILs has been explored with the upgradation of their physical, chemical, and biopharmaceutical properties, which enhance the opportunities for advances in pharmaceutical sciences.

The interaction of the surface active ionic liquid with nonionic surfactants (Triton X-100 and Triton X-405) in aqueous solution by using tensiometry method

The synergistic interactions of the surface active ionic liquid (1-dodecyl-3-methylimidazolium bromide, IL) with non-ionic surfactants TritonX-100 (TX-100) and TritonX-405 (TX-405) were investigated in aqueous solution at various mole fractions by using the surface tension technique at 298.15 K. In this work, the pendant drop method was used for surface tension measurement of solutions. The surfactant properties such as critical micelle concentration (CMC), micellar mole fractions (X1Rub), interaction parameter (βm), and activity coefficients of components in the mixed micelle (f1Rub and f2Rub) were calculated by theoretical Clint and Rubingh models. Also, surface and adsorption parameters, maximum surface excess values (Γmax), minimum area per molecule (Amin), surface tension at CMC (σCMC), and surface pressure at the CMC (πCMC) values have been estimated in (TX-405/TX-100 + IL + water) systems. The synergistic effects operating in these amphiphile mixtures were confirmed by the negative values of the interaction parameter. Generally, the CMC value of surfactant solution increases with the addition of ionic liquid in the mixture. It was demonstrated that IL can be judiciously used at different mole fractions for modifying the physicochemical properties of (TX-100 and TX-405). Different thermodynamics parameters were computed for mixtures and were also discussed in detail. The Gibbs free energy change of micellization (ΔGmo), the standard Gibbs energy of adsorption (ΔGado) and the excess free energy of micellization (ΔGexRub) values have been estimated at different compositions. The calculation of thermodynamic parameters shows that the micellization process is spontaneous and becomes more favorable with addition of the non-ionic component in mixture.

Adsorption of Saponin Natural Surfactant on Carbonate Rock and Comparison to Synthetic Surfactants: An Enhanced Oil Recovery Prospective

Surfactant flooding is one technique of chemical enhanced oil recovery (EOR) aimed at improving the microscopic displacement efficiency of trapped residual oil via reducing the oil–water interfacial tension and wettability alteration. Success of surfactant flooding strongly relies on surfactant loss through its adsorption onto reservoir minerals to ensure maximum transfer to target reservoir. The current study examines the adsorption behavior of saponin natural surfactant onto carbonate rock outcrops. As an environmentally friendly extract from plants, saponins have shown the potential to increase oil recovery, although saponin loss or adsorption on surfaces is yet to be studied. Common synthetic surfactants of various types (i.e., cationic and anionic) and different molecular structures (other nonionic surfactants) have also been studied to provide comparisons to saponin. The surfactant adsorption onto carbonate samples was studied by batch adsorption experiments, with the residual surfactant concentration determined by the surface tension technique. It was found that saponin, a natural nonionic surfactant, adsorbed less than the ionic surfactants, since saponin adsorption is not governed by electrostatic interactions but weaker hydrogen bonding. Such data concludes that saponins are likely to yield less retention than the ionic surfactants, but compared to other nonionic surfactants its retention is greater. This is likely attributed to differing surfactant molecular structures. Due to its branch-like structure with more terminal functional groups, saponin adsorbs more on the rock surface compared to other long-chain nonionic surfactants. The findings of the current study provide a useful guide in surfactant selection for EOR and highlight a potential of natural and environmentally friendly surfactants.

Ionic Liquid Green Assembly-Mediated Migration of Piperine from Calf-Thymus DNA: A New Possibility of the Tunable Drug Delivery System

Biocompatible surface-active ionic liquid (SAIL) was used first to study the deintercalation process of a well-known natural compound piperine (PIP) as an anticancer drug, obtained from PIP–calf thymus DNA (ctDNA) complex under controlled experimental conditions. In this study, we have been exploring the interaction of PIP in SAIL (1-butyl-3-methylimidazolium octyl sulfate ionic liquid ([C4mim][C8OSO3])), ctDNA, and deintercalation of PIP from the PIP–ctDNA complex through SAIL micelle using various spectroscopic techniques. Absorption, emission, and lifetime decay measurements provide strong evidence of the relocation of PIP molecules from ctDNA to SAIL micelle. Fluorescence quenching and steady-state fluorescence anisotropy were employed to examine the exact location of PIP in different media. Moreover, the surface tension technique was also employed to confirm the release of PIP molecules from the PIP–ctDNA complex in the presence of SAIL. Circular dichroism analysis suggested that SAIL micelle does not perturb the ctDNA structure, which supported the fact that SAIL micelle can be used as a safe vehicle for PIP. Overall, the study highlighted a novel strategy for deintercalation of drug using SAIL because the release of the drug can be controlled over a period by varying the concentration and composition of the SAIL.

An insight into a di-chain surfactant adsorption onto sandstone minerals under different salinity-temperature conditions: Chemical EOR applications

Surfactant flooding, a chemical enhanced oil recovery (EOR) technique, mainly aims at mobilizing the trapped residual oil by lowering the oil-water interfacial tension. The success of a surfactant flooding operation is strongly affected by surfactant loss through its adsorption on reservoir minerals. Therefore, the adsorption behavior of surfactants is of great importance and needs to be carefully investigated. The present study provides an insight into the adsorption behavior of a recently proposed surfactant, namely Aerosol-OT, on a number of minerals — including quartz-sand, kaolinite, illite, and montmorillonite — under different salinities and temperatures. The examination was carried out in the form of batch experiments, and the surface tension technique was implemented to determine the adsorption rate. The adsorption equilibrium data were examined through two adsorption isotherm models known as Langmuir and Freundlich. It was found that the adsorption rate increased with the increasing salinity, where the highest value was observed for kaolinite (21g/kg). However, an opposite trend occurred for temperature with the lowest adsorption rate (1.68g/kg) was obtained for quartz-sand at 85°C. The adsorption rate of Aerosol-OT was found to be higher than the conventional surfactants. A good correlation was seen between the equilibrium adsorption data and Langmuir isotherm model as their correlation coefficient (R2) exceeded 0.999. The results provide a useful tool to screen surfactants for the chemical EOR operation in clay-rich reservoirs.

Synthesis, physicochemical characteristics and antimicrobial studies of ethyl-substituted imidazolium-based surface active ionic liquids (SAILs)

A series containing higher members of ethyl-substituted imidazolium-based surface active ionic liquids (SAILs) [Cneim]Br, (n = 12, 14, 16) has been synthesized by a two-step reaction pathway. They were characterized by FT-IR, 1H NMR and 13C NMR and their effect on self-aggregation behavior in aqueous solution has been examined, employing conductometric and tensiometric methods besides fluorescence measurements and UV-visible spectroscopy. The conductivity data were recorded at different temperatures and thermodynamic parameters of micelle formation such as, standard Gibbs free energy (∆Gmo), standard enthalpy (∆Hmo), standard entropy (∆Smo) were evaluated. The process of micellization is entropy driven and supported by Gibbs free energy measurements. Interfacial parameters have also been evaluated by employing surface tension technique. The SAILs were also analyzed for their antimicrobial activity by taking eleven kinds of bacterial strains.

Effect of additives on mixed micellization of a phenothiazine drug promethazine hydrochloride and an ester-based pyridinium gemini surfactant

Promethazine hydrochloride (PMT) is a phenothiazine tranquilizer compound used as a sedative, analgesic, anticholinergic, antihistaminic and antipsychotic drug. The effect of various additives such as urea, glucose, glycine and sodium chloride (NaCl) on the mixed micellization of PMT and an ester-functionalized pyridinium gemini surfactant, (4, 4′-(propane-1, 3-diyl) bis (1-(2-(hexadecanoyl oxy) ethyl) dipyridinium bromide (16-3-16), has been studied at a constant temperature using surface tension, conductivity and fluorescence techniques. The different micellar and interfacial parameters were evaluated which signify the non-ideal behavior of all mixed systems. The thermodynamic studies revealed that the micellization and adsorption processes are spontaneous with the latter being more prominent than the former since the values of standard Gibbs free energy of adsorption ) are more negative than those of standard Gibbs free energy of micellization (). Besides, the excess free energy change of micellization () was determined which also showed negative values. These studies are specially aimed to get a deep understanding of the effect of different biologically significant molecules on the mixed micellization of the PMT-(16-3-16) micellar systems so as to ensure the bioavailability and effectiveness of the drug.

Effect of alkyl chain on micellisation properties of dodecylsulphate based surface active ionic liquids in aqueous solutions using conductance and surface tension techniques

ABSTRACT Two surface active ionic liquids (ILs) having 1-alkyl-3-methylimidazolium cationic moiety and dodecylsulphate based anionic moiety, i.e. [C5mim][DS] and [C7mim][DS], have been synthesised. 1H-NMR, thin layer chromatography was done for their characterisation. The electrical conductivity and surface tension measurements were performed to investigate the interfacial and bulk properties of the aqueous solutions of different alkyl chain ionic liquids. These techniques were employed to study the aggregation behaviour in aqueous conditions. Various surface active parameters were evaluated at 298.15 K from the surface tension measurements. The lowest surface tension (.) and maximum surface excess concentration () values showed that [C7mim][DS] had the highest surface activity. Conductance measurements were performed at three rising temperatures (288.15, 298.15, and 308.15) K, and their thermodynamic parameters were calculated. It indicated that micellisation of both ionic liquids was entropy driven at all temperatures.

Effect of alkyl chain on micellization properties of dodecylbenzenesulfonate based surface active ionic liquids using conductance, surface tension, and spectroscopic techniques

Two surface active ionic liquids (ILs) having 1-alkyl-3-methylimidazolium cationic moiety and dodecylbenzenesulfonate based anionic moiety i.e. [C5mim][DBS] and [C7mim][DBS], have been synthesized. 1H-NMR, thin layer chromatography were done for their characterization. These DBS-ILs have lower critical micelle concentration (CMC) in comparison with their conventional sodium dodecylbenzenesulfonate [Na][DBS] surfactants and hence are highly surface active. The conductance, surface tension, absorption (UV-visible) and emission (Fluorescence) techniques were used to determine the CMC values. DBS-ILs showed a remarkable absorption and emission spectra where intensity changes with variation in concentration of IL. Micelle self-assembly formation was also predicted by dynamic light scattering (DLS) technique. Conductance and surface tension techniques were employed to study the aggregation behavior in aqueous conditions. Various surface active parameters were evaluated at 298.15 K employing surface tension techniques. Conductance measurements were performed at three rising temperatures (288.15, 298.15, and 308.15) K and their thermodynamic parameters were calculated. From the above studies, the present synthesized ionic liquids found to have remarkable surface activity.

Effect of tocopherol on the properties of Pluronic F127 microemulsions: Physico-chemical characterization and in vivo toxicity

The development of biodegradable and biocompatible microemulsions to transport and deliver hydrophobic bioactive molecules is a fundamental challenge in pharmacological sciences. In the current work, oil-in-water Pluronic F127-based microemulsions using different fatty acids (sodium decanoate, SD, and sodium caprylate, SC) as co-surfactants were characterized as potential nanocarriers to solubilize and transport tocopherol (TOC) at Ow = [ethyl butyrate] / [Pluronic] = 1 and oil nanodroplet mass fraction (MFD) between 0.01 and 0.08 using dynamic light scattering (DLS) and dynamic surface tension (DST) techniques. DLS data showed that as the fatty acid chain length increased from sodium decanoate (SD) to sodium caprylate (SC), the nanodroplet size also did whereas the opposite behaviour was found as the MFD increased. DST data revealed that surface tension reached much faster the thermodynamic equilibrium for SD-stabilized compared to SC-stabilized Pluronic F127-based microemulsions. These were able to load important amounts of TOC with a high encapsulation efficiency. The release profile of the cargo compound from the microemulsions was sustained along time. In addition,2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity of TOC was examined, and results reported as the half maximal inhibitory concentration (IC50) values. Finally, to evaluate the potential cytotoxicity of the obtained TOC-loaded microemulsions preliminary in vivo experiments were performed. Microemulsions were parenterally administered in healthy rats and blood was collected to analyze serum levels of alanine aminotransferase (ALT), serum aspartate aminotransferase (AST), serum creatinine, serum blood urea nitrogen (BUN) and lactate dehydrogenase (LDH). Experimental data indicated a significant decrease in serum BUN and creatinine levels while other parameters remained unchanged. Also, the drug-loaded microemulsions-treated group showed symptoms of lethargy, nausea, and reduced food intake following injection, but no mortality was reported.

A systematic surface studies on the glycolipids to understand the surface adsorption behavior

Modular design of highly functionalized glycolipids from the natural origins provides attractive environmentally benign glycolipids with a wide range of interfacial applications. Linear correlation of single chain glycolipid’s surface properties at hydrophobic chain length ≥ 14 is a challenging task by using surface tension (ST) study. The interfacial area per molecule of the glycolipid is responsible for efficient molecular packing and surface activity at the interfaces. In this regard, ST and Langmuir-Blodgett (LB) techniques were collectively employed on a matrix of nine glycolipids with different headgroups at various alkyl chain lengths (C7-C21) to elucidate adsorption properties. Surface parameters obtained from ST studies in water as well as in 5 M aqueous NaCl solution has no trend, possible due to deviation from ideal surface behavior. Whereas, water and 5 M NaCl sub-phase LB studies provided a linear structure-property relationship for the glycolipids under investigation. Finally, ST and LB studies collectively reduced the ambiguity in understanding the surface behavior of the glycolipids.

A perfused human blood\u2013brain barrier on-a-chip for high-throughput assessment of barrier function and antibody transport

BackgroundReceptor-mediated transcytosis is one of the major routes for drug delivery of large molecules into the brain. The aim of this study was to develop a novel model of the human blood–brain barrier (BBB) in a high-throughput microfluidic device. This model can be used to assess passage of large biopharmaceuticals, such as therapeutic antibodies, across the BBB.MethodsThe model comprises human cell lines of brain endothelial cells, astrocytes, and pericytes in a two-lane or three-lane microfluidic platform that harbors 96 or 40 chips, respectively, in a 384-well plate format. In each chip, a perfused vessel of brain endothelial cells was grown against an extracellular matrix gel, which was patterned by means of surface tension techniques. Astrocytes and pericytes were added on the other side of the gel to complete the BBB on-a-chip model. Barrier function of the model was studied using fluorescent barrier integrity assays. To test antibody transcytosis, the lumen of the model’s endothelial vessel was perfused with an anti-transferrin receptor antibody or with a control antibody. The levels of antibody that penetrated to the basal compartment were quantified using a mesoscale discovery assay.ResultsThe perfused BBB on-a-chip model shows presence of adherens and tight junctions and severely limits the passage of a 20 kDa FITC-dextran dye. Penetration of the antibody targeting the human transferrin receptor (MEM-189) was markedly higher than penetration of the control antibody (apparent permeability of 2.9 × 10−5 versus 1.6 × 10−5 cm/min, respectively).ConclusionsWe demonstrate successful integration of a human BBB microfluidic model in a high-throughput plate-based format that can be used for drug screening purposes. This in vitro model shows sufficient barrier function to study the passage of large molecules and is sensitive to differences in antibody penetration, which could support discovery and engineering of BBB-shuttle technologies.

Equilibration of a Polycation-Anionic Surfactant Mixture at the Water/Vapor Interface.

The adsorption of concentrated poly(diallyldimethylammonium chloride) (PDADMAC)-sodium lauryl ether sulfate (SLES) mixtures at the water/vapor interface has been studied by different surface tension techniques and dilational viscoelasticity measurements. This work tries to shed light on the way in which the formation of polyelectrolyte-surfactant complexes in the bulk affects the interfacial properties of mixtures formed by a polycation and an oppositely charged surfactant. The results are discussed in terms of a two-step adsorption-equilibration of PDADMAC-SLES complexes at the interface, with the initial stages involving the diffusion of kinetically trapped aggregates formed in the bulk to the interface followed by the dissociation and spreading of such aggregates at the interface. This latter process becomes the main contribution to the surface tension decrease. This work aids our understanding of the most fundamental basis of the physicochemical behavior of concentrated polyelectrolyte-surfactant mixtures which present complex bulk and interfacial interactions with interest in both basic and applied sciences.

Synergistic effect of an antipsychotic drug chlorpromazine hydrochloride with pluronic triblock copolymer: A physicochemical study

Chlorpromazine is a psychiatric medication that belongs to the class of drugs called phenothiazine antipsychotics. It works by helping to restore the balance of certain natural substances in the brain. In the current study, the micellization behavior of chlorpromazine hydrochloride (CPZ) drug with Pluronic F-127 in the absence/presence of 0.1M NaCl at 298K temperature, has been studied. Tensiometric profile, for pure and mixtures of CPZ+F-127, generally consists of two breaks, whereas a single break is presents in pure CPZ tensiometric isotherm. Various bulk and interfacial parameters, such as critical micelle concentration (cmc), interaction parameter (β), maximum surface excess concentration (Γmax), effectiveness of surface tension reduction (πcmc), and other surface parameters at the interface have been estimated using a surface tension technique. Theories of Clint, Rosen, and Rubingh have been used to determine the theoretical cmc, interaction between amphiphiles at interface and micellar state of aggregation, and the composition of aggregates. The experimental cmc values of the mixed systems are lower than that of ideal one (cmcideal) over the entire mole fraction range of CPZ. A negative departure of cmc values from the ideal indicate that the mixed micelle formation occurs due to favorable mixing (synergistic interactions) in the mixed states. Several thermodynamic parameters have also been predicted from those theories. The interaction between the CPZ and Pluronic F–127 was also determined by extensive steady–state fluorescence measurements.

Interaction and binding efficiency of cationic drug chlorpheniramine maleate – anionic amino acid gemini surfactants mixture as media for the synthesis of silver nanoparticles

The advantages of drug–surfactant interactions as drug delivery vehicles are valuable for developing pharmaceutical formulations. The interaction of a drug, chlorpheniramine maleate (CPM), and (N,N′-dialkyl-N,N′-diacetate ethylenediamine, Ace(m)-2-Ace(n)), amino acid gemini surfactants (GSs) was investigated for various micellar, interfacial, and thermodynamic parameters at different mole fractions of CPM and GS mixtures using surface tension techniques. The values of the interaction parameter (β) suggested that CPM (cationic drug) exhibited low synergistic interactions with anionic GSs. Using UV measurement to evaluate the binding of CPM with GS, we determined the binding constant of drugs in the presence of GS and CPM+GS mixtures. Anionic GSs bound preferentially with CPM, because of the presence of cationic ions on the head group of the drug, and as an important drug-carrier, GSs showed higher binding constant (Kb) than that of ionic surfactant even at very low mole fractions. The values of different binding constant (Kb) indicated the binding mechanism of the CPM+GS mixed system. Mixed compositions of drug–surfactants were used to stabilize silver nanoparticles in aqueous media. The UV spectroscopy, dynamic light scattering, and transmission electron microscopy indicated a strong hydrophobic and the electrostatic interaction between CPM and GS. Specific morphologies were formed by adopting different supramolecular assemblies in aqueous media, depending on the internal packing arrangements and on the numbers of methylene units [–(CH2) n–].

Micelle Formation of Aerosol-OT Surfactants in Sea Water Salinity

Gemini surfactants group recently showed importance in screening techniques for the evaluation and selection of chemicals for enhanced oil recovery. Aerosol-OT (sodium bis (2-ethylhexyl) sulfosuccinate, AOT) is a versatile anionic Gemini surfactant which is widely used in the chemical and biophysical research, which is also included in the category of sulfonated hydrocarbons and shows high potential in laboratory experiments. In this paper, the micellar behaviour of anionic AOT in presence of high sodium salt concentration was studied at different temperature from (25–105) $$\,^{\circ }$$ C. Surface tension techniques using duoy ring were applied for each surfactant concentration to find the critical micelle concentration (CMC) at each temperature. Several thermodynamic parameters were also reported as the standard Gibbs energies of micellization, $$\Delta G^{0}$$ ; the standard enthalpy change of micellization, $$\Delta H^{0}$$ ; and the standard entropies of micellization, $$\Delta S^{0}$$ , were calculated from the temperature effect on the CMC. Results showed that CMC values increased with temperature. The enthalpy of micellization was found to be negative in all cases, and it showed a strong dependence on temperature in the AOT solution in the presence of high concentration of NaCl system.

Multi-technique approach towards amphiphilic drug-surfactant interaction: A physicochemical study

In the present work, we report the mixed micellization behavior of the phenothiazine drug chlorpromazine hydrochloride (CPZ) with surfactants (CTAB and 16-4-16) using surface tension, UV–visible, and fluorescence measurements. Various micellar and interfacial parameters such as critical micelle concentration (cmc), interaction parameter (β), the effectiveness of surface tension reduction (π), maximum surface excess concentration (Γmax) and minimum are per molecule (Amin) at the air-water interface have been evaluated using surface tension technique. The ideality/nonideality of mixed micelles is discussed with the help of Clint, Rubingh and Motomura's approaches. UV–visible and fluorescence results also support mixed micellization.

Synthesis and properties of amphiphilic thermo-sensitive block copolymers

Octadecyl acrylate (ODA) as hydrophobic monomer and N-isopropylacryamide (NIPAAm) as hydrophilic monomer were chosen to synthetize the thermo-sensitive block copolymers PODAx-PNIPAAmy-PODAx (BAB-type) via reversible-addition-fragmentation chain transfer (RAFT) polymerization, the block copolymers could self-assemble to flower-like micelles in aqueous solution with hydrophobic PODA as the inner core and stabilized by hydrophilic PNIPAAm as the outer shell. The characterizations of the micelles such as surfactivity, thermo-sensitivity, micelle hydrodynamic radius (Rh) and polydispersity index (PdI) were demonstrated by surface tension technique, UV-Vis, and dynamic light scattering (DLS) measurements, respectively. The longer the hydrophilic chain was, the higher the critical micellization concentration (CMC) would be, and the higher content of the PODA was, the lower the lower critical solution temperature (LCST) would be. The average Rh remained at about 100 nm below LCST, but decreased sharply to about 42 nm and kept constant when reaching and above LCST, which meant the non-aggregation of BAB type block copolymers. The micelle was homogeneous with the small PdI within the range of research. B0.5mA24mB0.5m had the largest capacity to encapsulate lipophilic Sudan Red IV model drugs and the drug loading efficiency was 9.76%.

Novel Quaternary Ammonium‐Based Cationic Surfactants: Synthesis, Surface Activity and Evaluation as Corrosion Inhibitors for C1018 Carbon Steel in Acidic Chloride Solution

AbstractA novel class of quaternary ammonium‐based cationic surfactants is synthesized and characterized via spectroscopic methods (FTIR, 1H NMR and 13C NMR). The surface properties, foaming power and biodegradability of the synthesized cationic surfactants are determined using the surface tension technique. The protection performance with their adsorption mechanisms for carbon steel is evaluated in a 15% HCl solution by a series of techniques including electrochemical impedance spectroscopy, potentiodynamic polarization curves, scanning electron microscopy (SEM), X‐ray spectroscopy, and UV–visible spectroscopy. The surfactants are found to be excellent corrosion inhibitors for carbon steel. The results show that the inhibition efficiencies are increased by increasing the concentration and the hydrophobic chain length of the tested compounds reaching the maximum at 250 ppm. The potentiodynamic polarization curves suggested that the inhibitors behave as a mixed type with predominant cathodic inhibition and the corrosion behavior can be explained by the adsorption film mechanism. Moreover, the mode of adsorption obeys the Langmuir adsorption isotherm; also, the adsorbed layer on the surface of the metal is approved by using SEM.

Studies on the Interaction Between Polyethylene Oxide and Cationic Gemini/Conventional Surfactants

The interactions of two gemini surfactants (16-s-16, s = 5, 6) and their conventional counterpart cetyltrimethylammonium bromide (CTAB) in water and in aqueous solutions of polyethylene oxide (PEO, molecular weight = 100,000) having concentrations of 0.1–0.75 wt.% have been investigated at different temperatures using surface tension, viscosity and scanning electron microscopy (SEM) techniques. The results indicate that there is interaction between PEO and CTAB/gemini surfactants. The driving force which is responsible for the interaction is supposed to be the minimization of interfacial force between the non-polar polymer parts and the solvent water by association. It is observed that critical micellization concentration (cmc) values increase with temperature. It was observed that cmc values for geminis are very small as compared to CTAB. Viscosity increases with increase in polymer concentration and is higher in case of geminis. Dense micellar arrangement is seen for geminis than cationic CTAB as evident from SEM images. The result shows that the interaction of geminis is much higher than its conventional surfactant with PEO.