Physicochemical studies of mixed surfactant microemulsions with isopropyl myristate as oil (original) (raw)
Related papers
Journal of Colloid and Interface Science, 2012
The present study is focused on the evaluation of the interfacial composition, thermodynamic properties, and structural parameters of water-in-oil mixed surfactant microemulsions [(cetylpyridinium chloride, CPC + polyoxyethylene (20) cetyl ether, Brij-58 or polyoxyethylene (20) stearyl ether, Brij-78)/ 1-pentanol/n-heptane, or n-decane] under various physicochemical environments by the Schulman method of cosurfactant titration of the oil/water interface. The estimation of the number of moles of 1-pentanol at the interface ðn i a Þ and bulk oil ðn o a Þ and its distribution between these two domains at the threshold level of stability have been emphasized. The thermodynamics of transfer of 1-pentanol from the continuous oil phase to the interface have been evaluated. n i a ; n i a , standard Gibbs free energy ðDG 0 t Þ, standard enthalpy ðDH 0 t Þ, and standard entropy ðDG 0 t Þ of transfer process have been found to be dependent on the molar ratio of water to surfactant (x), type of nonionic surfactant and its content (X Brij-58 or Brij-78 ), oil and temperature. A correlation between ðDH 0 t Þ and ðDS 0 t Þ is examined at different experimental temperatures. Bulk surfactant composition dependent temperature insensitive microemulsions have been reported. Associated structural parameters, such as droplet dimensions and aggregation number of surfactant and cosurfactant at the droplet interface have been evaluated using a mathematical model after suitable modifications for mixed surfactant systems. In light of these parameters, the prospect of using these microemulsion systems for the synthesis of nanoparticles and the modulation of enzyme activity has been discussed. Correlations of the results in terms of the evaluated physicochemical parameters have been attempted.
Journal of Surfactants and Detergents, 2010
Interfacial behavior, structural and thermodynamic parameters of a water/(surfactant+n-butanol)/n-heptane water-in-oil (w/o) microemulsion have been investigated using the dilution technique at different temperatures, and [water]/[surfactant] mole ratios. The cationic surfactants used were alkyltrimethyl ammonium bromides (CnTAB, n = 10, 14 and 16) while the nonionic surfactants were polyoxyethylene (20) sorbitan monoalkanoates (polysorbate), viz., palmitate (PS 40), stearate (PS 60) and oleate (PS 80). The distribution of cosurfactant between the oil–water interface and the bulk oil at the threshold level of stability, and the thermodynamics of transfer of the cosurfactant from the bulk oil to the interface were evaluated. Structural parameters such as the dimensions, population density and effective water pool radius of the dispersed water droplets in the oil phase and the interfacial population of the surfactant and cosurfactant have been evaluated in terms of the surfactant chain length.
Hypothesis: Although several studies on water-in-hydrocarbon oil microemulsions stabilized by anionic surfactant are available in literature, such study on oils possess comparable molar volumes with different chemical architectures and physicochemical properties, herein R-(+)-limonene (LIM) and isobutyl benzene (IBB) derived microemulsions in absence or presence of ionic liquid (IL) warrants uniqueness of this report. Experiments: The present study delineates interfacial composition and thermodynamics properties of sodium dodecylsulfate, SDS/1-pentanol/LIM or IBB/water microemulsions in absence or presence of IL, 1-butyl-3-methylimidazolium chloride (bmimCl) as additive by the dilution method. Further, precise characterization of these systems is accomplished by conductivity and DLS studies as function of ω, [bmimCl] and temperature, which provide an insight into unique features of the oil/water interface. Finally, the influence ofdistinctive features ofoils and the states ofwater organization in nanopool ofthese microemulsions have been explored from steady state fluorescence emission, fluorescence anisotropy and FTIR measurements. Findings: bmimCl containing microemulsions are more spontaneous than aqueous microemulsions. Addition of bmimCl yields smaller droplets compared to aqueous system. Fluorescence measurements reveal penetration of oil molecules in the surfactant palisade layer vis-a-vis interfacial micropolarity and their consequential effects in microenvironment of microemulsions in absence or presence of bmimCl, using suitable molecular probes. Apart from reciprocal variation in free and bound water with increasing water content, results exhibit mild variation in interfacial water (which is basically trapped water in the hydrophobic tail region of surfactant) by changing oil continuum. Finally, correlation of the results in terms of evaluated physicochemical and thermodynamic parameters has been presented.
Journal of Colloid and Interface Science, 2006
Phase diagrams of pseudo-quaternary systems of cetyltrimethylammonium bromide (CTAB)/polyoxyethylene(20)cetyl ether (Brij-58)/water/ 1-butanol (or 1-pentanol)/n-heptane (or n-decane) at fixed ω (= [water]/[surfactant]) of 55.6 were constructed at different temperatures (293, 303, 313, and 323 K) and different mole fraction compositions of Brij-58 (X Brij-58 = 0, 0.5, and 1.0 in CTAB + Brij-58 mixture). Pure CTAB stabilized systems produced larger single-phase domains than pure Brij-58 stabilized systems. Increasing temperature increased the single-phase domain in the Brij-58 stabilized systems, whereas the domain decreased in the CTAB stabilized systems. For mixed surfactant systems (with X Brij = 0.5) negligible influence of temperature in the studied range of 293 to 323 K on the phase behavior was observed. Interfacial compositions of the mixed microemulsion systems at different temperature and different compositions were evaluated by the dilution method. The n i a (number of moles of alcohol at the interface) and n o a (number of moles of alcohol in the oil phase) determined from dilution experiments were found to decrease and increase respectively for CTAB stabilized systems, whereas an opposite trend was witnessed for Brij-58 stabilized systems. The energetics of transfer of cosurfactants from oil to the interface were found to be exothermic and endothermic for CTAB and Brij-58 stabilized systems, respectively. At equimolar composition of CTAB and Brij-58, the phase diagrams were temperature insensitive, so that the enthalpy of the aforesaid transfer process was zero.
The Journal of Physical Chemistry, 1990
Ternary water-in-oil microemulsions using alkylbenzyldimethylammonium chloride (alkyl = dodecyl (N12), tetradecyl (N14), and hexadecyl (N16)) surfactants and benzene or chlorobenzene as oils have been investigated by means of electrical conductivity and NMR self-diffusion. The variations of the water self-diffusion coefficient with the [water]/[surfactant] molar concentration ratio w and with the volume fraction of benzene in the oil mixture in water/(benzene + chlorobenzene)/N16 microemulsions are well correlated with the changes of electrical conductivity, as expected from a model of microemulsions where the water cores of the droplets become increasingly connected above the percolation threshold. These connections, however, have a strongly dynamic character. This model permits us to explain the widely differing magnitudes of the changes of electrical conductivity, water self-diffusion coefficient, and rate of exchange of reactants between droplets upon increasing w. The self-diffusion coefficient of the oil has been found to be about half that of the bulk oil, as in studies reported by others.
The Journal of Physical Chemistry, 1987
A phase diagram investigation, by visual observation, has been performed at different temperatures on the system brine/ toluene/l-butanol/SDS for a 6.5% NaCl salinity and for a very low SDS concentration (0.01-0.3% w/w). In the range 16-26 O C a new behavior is detected, characterized by the appearance of a diffuse interface, a few millimeters thick. The composition and the structure of a typical sample have been investigated in that domain, as a function of temperature, by index of refraction, gas chromatographic, turbidity, and quasi-elastic light scattering measurements. The sample is composed of an upper transparent region of the oily type and a lower turbid region of the oil/water (o/w) microemulsion type, separated by a sharp interface; the diffuse interface appears between two regions of different turbidity and composition of the lower aqueous domain. To interpret the nonuniformity of the aqueous domain a discussion is provided in terms of incomplete phase separation, critical type regime, sedimentation of polydisperse globules due to gravity, and globules aggregation. A detailed analysis of the composition profile allows to pinpoint a peculiar composition of the interfacial film with a much higher alcohol/SDS ratio than usual which could be the origin of the new behavior. graphic measurements. We thank Professor B. Widom and Professors C. M. Knobler and J. Wheeler for very stimulating discussions. C. G. is grateful to Prof. P. G. de Gennes for his kind hospitality and for helpful discussions and criticisms during the course of this work. She thanks the Italian Foundation "Angel0 Della Riccia" and the Italian C.N.R. for financial support which made it possible for her to start in this work.
The Journal of Physical Chemistry, 1990
Ternary water-in-oil microemulsions using alkylbenzyldimethylammonium chloride (alkyl = dodecyl (N12), tetradecyl (N14), and hexadecyl (N16)) surfactants and benzene or chlorobenzene as oils have been investigated by means of electrical conductivity and NMR self-diffusion. The variations of the water self-diffusion coefficient with the [water]/[surfactant] molar concentration ratio w and with the volume fraction of benzene in the oil mixture in water/(benzene + chlorobenzene)/N16 microemulsions are well correlated with the changes of electrical conductivity, as expected from a model of microemulsions where the water cores of the droplets become increasingly connected above the percolation threshold. These connections, however, have a strongly dynamic character. This model permits us to explain the widely differing magnitudes of the changes of electrical conductivity, water self-diffusion coefficient, and rate of exchange of reactants between droplets upon increasing w. The self-diffusion coefficient of the oil has been found to be about half that of the bulk oil, as in studies reported by others.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2000
Sub-zero temperature differential scanning calorimetry (SZT-DSC) has been applied to a model nonionic water-inoil microemulsion system based on: sucrose esters/water/1-butanol/n-alkanes (C 12 -C 16 ). The maximum water solubilization was 40, 56 and 80 wt.% for the systems containing n-dodecane, n-tetradecane and n-hexadecane as the oil phase, respectively. Two types of solubilized water have been detected. The so-called 'bulk' (free) water present in the core of the microemulsion and the 'interfacial' (bound) water attached at the interface to the surfactant (and/or butanol). The internal distribution of the water within the microemulsions was determined along two dilution lines (with 32 and 43 wt.% of the initial surfactant). It was found that for the n-dodecane system the maximum 'interfacial'(bound) water is 12 and 14 wt.% along the two dilution lines, respectively. Above this water content a core of 'bulk' (free) water is formed. The type of the oil and the butanol interfacial participation strongly affect the water internal distribution. Both the temperature of fusion, T f , of the 'bulk' (free) water and of the 'interfacial' (bound) water are strongly affected by the butanol and the oil. The nature of the surfactant, its fatty chain length and its HLB also affect the binding capabilities and capacity of water in microemulsion systems. For both n-dodecane and n-hexadecane, 11-13 molecules of water can be bound to the surfactant at the interface.
Light-scattering investigations on dilute nonionic oil-in-water microemulsions
AAPS PharmSci, 2000
Dilute 3-component nonionic oil-in-water microemulsions formulated with either a polyoxyethylene surfactant (C 18:1 E 10 or C 12 E 10) or the alkylamine-N-oxide surfactant, DDAO (C 12 AO), and containing either a triglyceride or an ethyl ester oil have been examined using dynamic and static lightscattering techniques. Analysis of the results showed distinct differences in the tested oil's mode of incorporation into the microemulsion droplets, with both the molecular volume of the oil and the hydrophobic chain length of the surfactant being important. For example, microemulsions formulated by C 18:1 E 10 and containing one of the larger molecular volume oils (that is, either a triglyceride, Miglyol 812, or soybean oil) or the ethyl ester of fatty acid oil, ethyl oleate, exhibited first a decrease and then an increase in hydrodynamic size and surfactant aggregation number, suggesting that the asymmetric C 18:1 E 10 micelles became spherical upon the addition of a small amount of oil and grew thereafter because of further oil being incorporated into the core of the spherical microemulsion droplet. A similar conclusion of sphericity could not be drawn for microemulsions stabilized by C 18:1 E 10 and containing one of the oils smaller in molecular volume (namely tributyrin, ethyl butyrate, or ethyl caprylate) where neither the aggregation number nor the hydrodynamic radius changed much upon the addition of oil. This result suggested that these oils were preferentially located in the interfacial surfactant monolayer, behaving in much the same way as a cosurfactant. A different trend of results, however, was seen for microemulsions prepared
Model microemulsions containing vegetable oils part 1: Nonionic surfactant systems
Journal of the American Oil Chemists Society, 1989
aKarishamns AB, Division R&D, S-374 82 Karlshamn, Sweden and blnstitute for Surface Chemistry, S-114 86 Stockholm, Sweden Nonionic microemulsions containing triglycerides and fatty acid esters as lipophilic components have been studied. The phase inversion temperature (PIT) of the systems was determined by a conductometric method. Partial phase diagrams were constructed in the phase inversion temperature range. Water solubilization capacity of the nonionic surfactant systems studied was dependent on surfactant and oil types in analogy to ordinary hydrocarbon systems. The PIT:s increased with increased molecular weight for both esters and triglycerides.