Benzyldimethyldodecylammonium Bromide Research Articles

Gold nanoparticles for surface-enhanced Raman scattering detection of benzyldimethyldodecylammonium chloride at low concentration

The oil and gas industry plays a vital role in the global economy. The production process has several critical conditions and can expose metals to corrosion. Surfactants like the quaternary ammonium salt Benzyldimethyldodecylammonium Bromide (BDAC) are currently used to prevent corrosions; classical methods for determining these surfactants have problems in saline samples and usually present high costs. In this context, spectroscopic techniques become an excellent alternative for quaternary ammonium salts detection. Here, a SERS (surface-enhanced Raman scattering) sensor based on gold nanoparticles (AuNPs) synthesized through chemical reduction was used as an alternative method for BDAC detection. We detected BDAC at low concentrations in water solutions: at 5 to 30 ppm (1.47 × 10−5 mol L−1 to 8.82 × 10−5 mol L−1); and had the vibration attempt attribute analyzed. A new study of quaternary ammonium compounds using AuNPs and SERS with a different, easy, and repeatable approach to spectra acquisition is presented and shows to be a promising method applied in quaternary ammonium salt compounds detection for the oil and gas industry.

Mechanistic pathways of cationic and anionic surfactants sorption by kaolinite in water.

Surfactants are widely used in many chemical industries and as primary components of cleaning detergents due to their specific characteristics, which in turn results in high pollution of domestic and industrial wastewaters by such substances. In this study, the mechanistic pathways of the adsorption of cationic benzyl-dimethyl-dodecyl ammonium bromide (BDDAB) and anionic sodium dodecyl sulfate (SDS) surfactants on kaolinite clay in water were investigated. The results showed that the adsorption of anionic surfactant (SDS) on kaolinite is better compared with cationic surfactant (BDDAB), wherein the ♦maximum adsorption capacity was found 161.4μmolg-1 and 234μmolg-1 for BDDAB and SDS, respectively. Adsorption kinetics were the best suited to pseudo-second-order model for both BDDAB and SDS with an adsorption rate constant of 0.028gμmol-1min-1 and 0.023gμmol-1min-1, respectively. Meanwhile, the adsorption of BDDAB by kaolinite showed that the isotherm adsorption tended to follow the Langmuir-Freundlich and Freundlich isotherm models. However, the SDS adsorption isotherm obeyed only the Langmuir-Freundlich model.

Analysis of Adsorbed Layers of Benzyldimethyldodecylammonium Bromide on Silica Particles in Water Using the Sorbent Mass Variation Method

A "sorbent mass variation" (SMV) method has been suggested to investigate the adsorption at solid-liquid interfaces, which can provide information on the adsorbed layer structure including its thickness and composition. However, there has been little research focused on the method, and therefore, it is essential to examine its general applicability. Herein, the adsorption of benzyldimethyldodecylammonium bromide (BDDABr), a cationic surfactant, on silica (SiO2) nanoparticles (with ∼12 and 24 nm in size, denoted as S-SiO2 and L-SiO2, respectively) in water was investigated using the SMV method. The adsorption isotherms all show a linearly declining tendency in the saturated adsorption regime, consistent with the prediction of the SMV model. The adsorption is interpreted to form noncomplete bilayers (or isolated admicelles). The thicknesses of the adsorbed bilayers on S-SiO2 and L-SiO2 are estimated to be ∼2.9 and 2.7 nm, respectively, and the volume fractions of BDDABr in the saturated adsorbed layers are 0.63 and 0.68, respectively. In addition, the change in the Gibbs free energy of the adsorption process is also analyzed, showing its spontaneous nature. This work demonstrates that the SMV method is available for investigation on the adsorption of surfactants at solid-liquid interfaces, which can provide information on the structure and formation thermodynamics of adsorbed layers.

Adsorption of benzyldimethyldodecylammonium bromide on silica nanoparticles in water

Adsorption of the cationic surfactant benzyldimethyldodecylammonium bromide (BDDABr) on silica nanoparticles with ~ 12 and 31 nm in size (denoted as S-SiO2 and L-SiO2, respectively) is investigated at various solid dosages (Cs, 10–40 g/L), pH (3–10), and temperature (T, 298–308 K). No Cs-effect is observed in the adsorption. However, it is interestingly found that, besides pH and T, the size of the silica particles has an obvious influence on the adsorption. The adsorption may show the Langmuir type (L-type), S-type, and “double plateau” type (LS-type) isotherms, depending on silica particle sizes and pH. Increasing pH may lead to a change in the isotherm types from S-type through LS-type to L-type. The S-type and LS-type isotherms can be adequately described using the one-step and two-step surface micellization models, respectively. The affinity of the S-SiO2 toward BDDABr is lower than that of the L-SiO2, consistent with the dissociation tendency of their surface hydroxyl groups.

Evaluation of the intensifying effect of quaternary ammonium salts in the course of dyeing of cellulose materials with active dyes

The effect of quaternary ammonium salts on batch dyeing of cellulose materials with active dyes was examined. The use of benzyldimethylhexadecylammonium chloride and benzyldimethyldodecylammonium bromide as intensifi ers in dyeing of cellulose textile materials with active dyes of vinyl sulfone and monochlorotriazine types allows high intensity and durability of the color to be attained owing to increased degree of covalent fi xation of the dyes and their decreased desorption in the course of washing of the dyed material.

Wettability, adhesion, adsorption and interface tension in the polymer/surfactant aqueous solution system: II. Work of adhesion and adsorption of surfactant at polymer–solution and solution–air interfaces

The values of the surface tension of aqueous solutions of Triton X-100, Triton X-114, Triton X-165, sodium dodecylsulfate, sodium hexadecylsulfonate, cetyltrimethylammonium bromide, cetylpyridinium bromide, sodium N-lauryl sarcosinate, dodecyldimethyethylammonium bromide, tetradecyltrimethylammonium bromide and benzyldimethyldodecylammonium bromide and those of contact angle measured in the polytetrafluoroethylene (polymethyl methacrylate, nylon 6)–solution–air system were applied for the studies of correlation between the adsorption of surfactants at the solution–air and polymer–solution interfaces, critical surface tension of polymer wetting and work of adhesion of aqueous solutions of these surfactants to the above mentioned polymer surfaces. On the basis of the surface tension of aqueous solutions of surfactants studied and polymer–solution interface tension the Gibbs surface excess concentration at the polymer–solution interface was calculated and compared to that at the solution–air one. Using the Gibbs surface excess concentration data the molar fraction of surfactants at the polymer–solution interface was determined and compared to that at the solution–air one. The values of the activity of surfactants at the polymer–solution interface obtained from the Sprow and Prausnitz equation were also compared to those at the solution–air one and next used for calculations of the work of adhesion of solution to the polymer surface. The obtained values were compared to those determined from the Young–Dupree equation.

Wettability, adhesion, adsorption and interface tension in the polymer/surfactant aqueous solution system. I. Critical surface tension of polymer wetting and its surface tension

The contact angle of aqueous solutions of Triton X-100, Triton X-114, Triton X-165, sodium dodecylsulfate, sodium hexadecylsulfonate, cetyltrimethylammonium bromide, cetylpyridinium bromide, sodium N-lauryl sarcosinate, dodecyldimethyethylammonium bromide, tetradecyltrimethylammonium bromide and benzyldimethyldodecylammonium bromide on polytetrafluoroethylene, polymethyl methacrylate and nylon 6 was studied. The contact angle values were used in the Young equation for the polymer–solution interface tension calculation and for the determination of the critical surface tension of polymer wetting. The critical surface tension of polymer wetting was obtained on the basis of the relationship between the cosine of contact angle and/or the adhesion tension as a function of the surface tension of aqueous solution of studied surfactants and then was discussed in relation to the Lifshitz–van der Waals components and electron-acceptor and electron-donor parameters of polytetrafluoroethylene, polymethyl methacrylate and nylon 6 surface tension. The role of the parameter of interfacial interactions in the relationship between the critical surface tension of polymer wetting and the surface tension was also considered. This parameter was calculated by using the polymer–solution interface tension as well as the polymer and aqueous solutions of surfactant surface tension.

Critical micelle concentration of some surfactants and thermodynamic parameters of their micellization

Measurements of density, viscosity, conductivity and light scattering of aqueous solutions of sodium dodecylsulfate (SDDS), sodium hexadecylsulfonate (SHS), sodium N-lauryl sarcosinate (SDSa), cetyltrimethylammonium bromide (CTAB), cetylpyridinium bromide (CPyB), dodecyldimethyethylammonium bromide (DDEAB), tetradecyltrimethylammonium bromide (TTAB), benzyldimethyldodecylammonium bromide (BDDAB) and Triton X-100 (TX-100), Triton X-114 (TX-114), Triton X-165 (TX-165) were carried out at different temperatures. On the basis of the results obtained from these measurements critical micelle concentration, aggregation number, apparent and partial molar volume, standard Gibbs energy, enthalpy and entropy were calculated. In the case of ionic surfactants the degree of surfactant dissociation in micelle was taken into account. There was also determined the standard Gibbs energy of micellization using hydrophobic tail-water, hydrophilic head-water interfacial free energy and electrostatic intermolecular interactions. Then the results were compared with those obtained by other methods and the literature data. The presence of micelles at the concentration of aqueous surfactant solutions determined by the above mentioned methods was confirmed by the light scattering measurements.

Activity and thermodynamic parameters of some surfactants adsorption at the water–air interface

Measurements of the surface tension of aqueous solutions of Triton X-100, Triton X-114, Triton X-165, sodium dodecylsulfate, sodium hexadecylsulfonate, cetyltrimethylammonium bromide, cetylpyridinium bromide, sodium N-lauryl sarcosinate, dodecyldimethylethylammonium bromide, tetradecyltrimethylammonium bromide and benzyldimethyldodecylammonium bromide were made at different temperatures. On the basis of the obtained results the activity of the surfactants at the water–air interface was determined and discussed based on the intermolecular interactions. The surfactant activity at the water–air interface was taken into account for determination of thermodynamic parameters of surfactant adsorption using the Langmuir method and the Szyszkowski equation. The thermodynamic parameters were also determined by means of the Rosen and Aronson, Gamboa and Olea methods as well that based on the changes of tail–water interface tension to that of tail–air.

Effects of head group of cationic surfactants on the hydrolysis of p‐nitrophenyl acetate catalyzed by α‐chymotrypsin

AbstractThe kinetics of hydrolysis of p‐nitrophenyl acetate catalyzed by α‐chymotrypsin (α‐CT) has been studied in the presence of several cationic surfactants having different head groups maintaining the dodecyl hydrophobic residue and bromide counterion. The enzyme activity was tested in the presence of dodecyl trimethylammonium bromide (DTAB), dodecylpyridinium bromide (DPB), dodecyldimethylethanolammonium bromide (DDMEAB), dodecyldiethylethanolammonium bromide (DDEEAB), benzyldimethyldodecylammonium bromide (BDDAB), and dodecyltriphenylphosphonium bromide (DTPB) surfactants. The extent of superactivity depends upon head groups of surfactants. The activity of α‐CT depends on the surfactant concentration and it varies with the surfactant head group dimensions (DTPB > DDEEAB > DTAB > BDDAB > DDMEAB > DPB). For all surfactants, DTPB exhibits highest superactivity. The effects of surfactants on the apparent kinetic parameters like Michaelis constant Km and the catalytic constant kcat have been determined. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 377–381, 2009

Surface and volume properties of dodecylethyldimethylammonium bromide and benzyldimethyldodecylammonium bromide: I. Surface properties of dodecylethyldimethylammonium bromide and benzyldimethyldodecylammonium bromide

Surface tension measurements were carried out for aqueous solutions of two cationic surfactants: dodecylethyldimethylammonium bromide (C 12(EDMAB)) and benzyldimethyldodecylammonium bromide (BDDAB). Isotherms and thermodynamic adsorption parameters were determined from the surface tension data. Firstly, the surface excess concentration in the adsorbed monolayer and the total concentration of the surfactants were determined, then the standard free energy of adsorption was calculated by different methods. In the calculations, different orientations of the surfactants at the adsorbed monolayer were also taken into account. From the experimental and calculated data it results that the difference in the structure of the two cationic surfactants by changing the methyl group for aryl one in their heads causes an increase of the efficiency and a decrease of the effectiveness of adsorption at water–air interface, and that the standard free energy of adsorption can be predicted from the surface tension of the surfactants assuming the aryl group to be equivalent to 3.5 methylene groups. The experimentally obtained difference between the standard free energy of adsorption of the C 12(EDMAB) and BDDAB was in good agreement with that theoretically accounted, corresponding to the standard free energy of adsorption of the aryl group. However, the best correlation between the values was obtained when a parallel orientation of the surfactant molecules at the adsorbed monolayer was taken into account.

Surface and volume properties of dodecylethyldimethylammonium bromide and benzyldimethyldodecylammonium bromide: II. Volumetric properties of dodecylethyldimethylammonium bromide and benzyldimethyldodecylammonium bromide

Density measurements were carried out for aqueous solutions of two cationic surfactants: dodecylethyldimethylammonium bromide (C 12(EDMAB)) and benzyldimethyldodecylammonium bromide (BDDAB). On the basis of the obtained results of the measurements the CMC and partial molar volumes of the surfactants studied were also determined. The obtained CMC values were also analyzed with those accounted on the basis of the surface tension data from the previous paper [J. Harkot, B. Jańczuk, J. Colloid Interface Sci. (2008), submitted for publication]. The values of CMC determined from the surface tension and density measurements for C 12(EDMAB) are equal to 9.9 × 10 −3 and 1.5 × 10 −2 M and for BDDAB to 5.25 × 10 −3 and 5.3 × 10 −3 M , respectively. These obtained values are very similar. However, in the literature it is difficult to find the CMC values for C 12(EDMAB) and BDDAB determined by these two methods used by us—especially from the density measurements for BDDAB and surface tension measurements for C 12(EDMAB). In the case of the apparent molar volumes of C 12(EDMAB) there is a good agreement between the values obtained by us and those found in the literature. The CMC values for C 12(EDMAB) and BDDAB were also determined on the basis of their surface tension and free energy of electrostatic interactions between the polar heads of these surfactants and compared with those obtained from the surface tension and density measurements. It was found that the theoretically obtained CMC values were close to those determined from the density and surface tension data for the C 12(EDMAB) and that the ratios of the CMC values of the surfactants to their concentration at which the water surface tension decreased by about 20 mN/m proved that the presence of the aryl group in the BDDAB head instead of the methyl group caused that its micellization process was more inhibited in relation to its adsorption at air–water interface than that of C 12(EDMAB).

The role of adsorption of dodecylethyldimethylammonium bromide and benzyldimethyldodecylammonium bromide surfactants in wetting of polytetrafluoroethylene and poly(methyl methacrylate) surfaces

The role of adsorption of dodecylethyldimethylammonium bromide (C12(EDMAB)) and benzyldimethyldodecylammonium bromide (BDDAB) at water–air and polytetrafluoroethylene (PTFE)–water and poly(methyl methacrylate) (PMMA)–water interface, in wetting of PTFE and PMMA surface, was established from the measured values of the contact angle (θ) of aqueous C12(EDMAB) and BDDAB solutions in PTFE (PMMA)-solution drop–air system, and from the measured values of the surface tension of aqueous C12(EDMAB) and BDDAB solutions. Adsorption of C12(EDMAB) and BDDAB at water–air interface was determined earlier from the Gibbs equation. Adsorption at solid–water interface was deduced from the Lucassen-Reynders equation based on the relationship between adhesion tension (γLVcosθ) and surface tension (γLV). The slope of the γLVcosθ–γLV curve was found to be constant and equal to −1, and about −0.3 for PTFE and PMMA surface, respectively (in the case of both surfactant studied: C12(EDMAB) and BDDAB, and in the whole range of surfactants concentration in solution). It means that the amount of the surfactant adsorbed at the PTFE–water interface, ΓSL, was essentially equal to its amount adsorbed at water–air interface, ΓLV. However, ΓSL at the PMMA–water interface was about three times smaller as compared to that at water–air interface. By extrapolating the linear dependence between γLVcosθ–γLV and dependence between cosθ–γLV and cosθ=1 we determined the value of the critical surface tension of PTFE and PMMA surface wetting, γc. The obtained values of γc for PTFE surface were equal 23.4 and 23.8mN/m, 23.1 and 23.2mN/m for C12(EDMAB) and BDDAB, respectively and they were higher than the surface tension of PTFE (20.24mN/m). On the other hand, the obtained values of γc for PMMA surface were equal 31.4 and 30.9mN/m, 31.7 and 31.3mN/m for C12(EDMAB) and BDDAB, respectively and they were smaller than the surface tension of PMMA (39.21mN/m). Using the values of PTFE and PMMA surface tension and the measured values of the surface tension of aqueous C12(EDMAB) and BDDAB solutions in the Young equation, the PTFE (PMMA)-solution interfacial tension, γSL, was also determined. Next, the work of adhesion (WA) was deduced, and it occurred that the dependence between the WA and the surface tension (γLV) for both studied solids was linear. However, the values of the WA for PMMA change as a function of logC (C—surfactant concentration) changed from 91.7 to 68.5mJ/m2 and from 91.8 to 65.1mJ/m2 for C12(EDMAB) and BDDAB, respectively. On the other hand, the work of adhesion of both studied surfactants solutions to the PTFE surface was practically constant (an average value was equal 45.8 and 45.4mJ/m2, respectively). These values were close to the value of the work of water adhesion to PTFE surface (45.5mJ/m2).

Release characteristics of anionic drug compounds from liquid crystalline gels: Part II. The effects of ion pairing and buffering on the passive delivery of anionic drugs across non-rate-limiting membranes

This is the second in a series of papers that report on the release and transport of a range of anionic drugs (diclofenac, salicylic acid) from liquid crystalline gels and ultimately on their use in transdermal delivery. The previous paper [Fitzpatrick, D., Corish, J., 2005. Release characteristics of anionic drug compounds from liquid crystalline gels for transdermal delivery. Part I. Passive release across non-rate limiting membranes. Int. J. Pharm. 301, 226–236] investigated passive release profiles across a non-rate-limiting membrane: here we report on the search for a suitable model enhancer (benzyl dimethyldodecyl ammonium bromide) for the transdermal delivery of anionic compounds. The results presented reveal a significant role for ion pairing and for buffering, analogous to those found in the investigations of cationic species (salbutamol) by Nolan, L.M.A., Corish, J., Corrigan, O.I., Fitzpatrick, D., 2003. Iontophoretic and chemical enhancement of drug delivery. Part I. Across artificial membranes. Int. J. Pharm. 12, 41–55. The method of vehicle preparation is also investigated. It is shown that ion pairing of the drug with the enhancer decreases the amount of drug available for transport from the liquid crystalline gels into aqueous receptor media. This decrease is directly related to the ratio of the concentration of drug to that of the enhancer. Buffering the vehicle inhibits the ion-pair formation to some extent. Vehicle preparation was also found to influence the degree of ion-pair association. The inclusion of a similarly charged enhancer (oleic acid) to the drug was found not to impede the diffusion of the drug from the gels.

The binding of benzyldimethyldodecylammonium bromide to acrylamide-co-sodium-2-acrylamido-2-methylpropanesulfonate copolymers: thermodynamical and conformational aspects

The binding isotherms of benzyldimethyldodecylammonium bromide (BDDAB) to copolymers of acrylamide and sodium-2-acrylamido-2-methylpropanesulfonate (AMPS), 5 or 20% in mole ratios (AMPS5 and AMPS20, respectively), are determined by membrane ultrafiltration and analysed with the Satake–Yang formalism in terms of binding constants and cooperativities. Complexation is further investigated by steady-state fluorescence of solubilized pyrene, dynamic light scattering (DLS) and laser Doppler electrophoresis (LDE). Hydrophobic aggregates bound to AMPS20 appear similar to BDDAB free micelles, whereas those borne by AMPS5 increase in size more distinctly under the non-stoichiometric complexation mechanism. Multimolecular association and dissociation equilibria are displayed by DLS in the AMPS5 biphasic domain. Above the critical aggregation concentration, electrophoretic mobilities of the complexes initially remain unchanged by compensation of antagonistic electrostatic contributions. Upon progressive binding of micelles the charge-to-friction ratio of the polyons is reduced by condensation of the counter-ions.

Analysis of benzyldimethyldodecylammonium bromide in chemical disinfectants by liquid chromatography and capillary electrophoresis

Two novel analytical methodologies using capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) were developed and compared for the determination of benzyldimethyldodecylammonium bromide (BAB) in commercial compound chemical disinfectants. The LC analysis was performed with a Kromasil C 18 ( 200 mm ×4.6 mm, 5 μm) column and a mobile phase of A:B=80:20 (A: acetonitrile, B: 4 mmol/L octanesulfonic sodium—0.02 mol/L acetic sodium, adjusted with acetic acid to pH 5.2) at a flow rate of 1.0 mL/min. Detection was by ultraviolet absorption at 262 nm. The CE analysis was performed in a bare fused-silica capillary with 75 μm i.d. and total length of 46.4 cm with a buffer solution of 50% acetonitrile −50 mmol/L NaH 2 PO 4 , pH 2.24. The applied voltage was 20 kV. Detection was by ultraviolet absorption at 214 nm. Under optimized conditions, the HPLC retention time and CE migration time for BAB was 9.18 and 5.08 min, respectively. Calibration curves of peak area versus concentration gave correlation coefficients of 0.9996 for HPLC and 0.9994 for CE. The detection limits for HPLC and CE were 1.6 mg/L and 0.2 mg/L, respectively. Average recoveries at three concentration levels (50, 100, 200 mg/L for HPLC; 20, 40, 100 mg/L for CE) were 99.94±1.5, 99.64±1.3 and 99.61±0.4% for HPLC and 120.47±2.6, 102.06±8.7 and 103.05±3.0% for CE, respectively. Although both methods were shown to be suitable for the determination of BAB in commercial disinfectant compounds, CE provided analysis with less solvent purchase/disposal and better column efficiency, whereas HPLC provided superior precision.

Analysis of benzyldimethyldodecylammonium bromide in chemical disinfectants by liquid chromatography and capillary electrophoresis

Two novel analytical methodologies using capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) were developed and compared for the determination of benzyldimethyldodecylammonium bromide (BAB) in commercial compound chemical disinfectants. The LC analysis was performed with a Kromasil C 18 ( 200 mm×4.6 mm, 5 μm) column and a mobile phase of A:B=80:20 (A: acetonitrile, B: 4 mmol/L octanesulfonic sodium—0.02 mol/L acetic sodium, adjusted with acetic acid to pH 5.2) at a flow rate of 1.0 mL/min. Detection was by ultraviolet absorption at 262 nm. The CE analysis was performed in a bare fused-silica capillary with 75 μm i.d. and total length of 46.4 cm with a buffer solution of 50% acetonitrile −50 mmol/L NaH 2PO 4, pH 2.24. The applied voltage was 20 kV. Detection was by ultraviolet absorption at 214 nm. Under optimized conditions, the HPLC retention time and CE migration time for BAB was 9.18 and 5.08 min, respectively. Calibration curves of peak area versus concentration gave correlation coefficients of 0.9996 for HPLC and 0.9994 for CE. The detection limits for HPLC and CE were 1.6 mg/L and 0.2 mg/L, respectively. Average recoveries at three concentration levels (50, 100, 200 mg/L for HPLC; 20, 40, 100 mg/L for CE) were 99.94±1.5, 99.64±1.3 and 99.61±0.4% for HPLC and 120.47±2.6, 102.06±8.7 and 103.05±3.0% for CE, respectively. Although both methods were shown to be suitable for the determination of BAB in commercial disinfectant compounds, CE provided analysis with less solvent purchase/disposal and better column efficiency, whereas HPLC provided superior precision.

Application of ordered mesoporous silica in adsolubilisation of alcohols by conventional and gemini cationic surfactants

Application of ordered porous silica in adsolubilisation of primary and aromatic alcohols by conventional and gemini cationic surfactants has been tested in aqueous media at 298 K. Benzyldimethyldodecylammonium bromide (BDDAB) and two alkanediyl-α,ω-bis(dodecyldimethylammonium bromide) surfactants (C 12C SC 12) with ethanediyl (C 2) or hexanediyl (C 6) spacer were adsorbed onto microporous SiAl32 d18 or mesoporous SiAl32 d50 aluminosilicate of the MCM-41 type (the framework Si:Al ratio is equal to 32; d18 or d50 refers to the mean pore diameter in angstroms). The reversibility of adsorption of both surfactant ions, i.e. the surface-active cation and its counter-ion, the ion exchange with sodium cations, the evolution of some other parameters with surfactant adsorption, such as the pH of the equilibrated supernatant, the electrophoretic mobility of the solid particles and the differential molar enthalpy of displacement, were first studied taking BDDAB and purely siliceous Si d29 as an example of the adsorption system. Adsolubilisation of 1-butanol (C 4OH) by BDDAB adsorbed onto SiAl32 d18 and SiAl32 d50 was quantified either as a function of the equilibrium alcohol concentration at a fixed surfactant content of 12 mmol kg −1 or as a function of the surfactant concentration from a 10 mmol kg −1 NaBr solution at a fixed alcohol content of 10 mmol kg −1. The uptake of phenol (PhOH) by C 12C SC 12–SiAl32 d50 systems was monitored as a function of the equilibrium surfactant concentration at a fixed alcohol content of 1.5 mmol kg −1. The individual adsorption isotherms of the surface-active cation and alcohol additive were supplemented by the measurements of the differential molar enthalpy of displacement in systems with and without additive. Transfer of solubilisate molecules from the aqueous phase to the interfacial aggregates contributes to the overall exothermicity of the displacement phenomenon. Compared to non-porous silica supports, ordered mesoporous aluminosilicates are much more efficient as adsolubilisation host systems for low molecular weight alcohols.

Effect of alcohol addition to the aqueous phase on the thermal effects of micellization of cationic benzyldimethyldodecylammonium bromide and its adsorption onto porous and nonporous silicas

Titration calorimetry has been used to study the effect of the addition of two primary alcohols, 1-butanol and 1-heptanol, to the aqueous phase on the thermal effects of micellization of benzyldimethyldodecylammonium bromide (BDDAB) as well as its adsorption onto nonporous Spherosil XO15M and onto porous aluminosilicate SiAl32 d 22 possessing uniformly sized mesopores. A linear decrease of the critical micelle concentration (CMC) of the cationic surfactant with the additive content was inferred from the specific conductivity measurements. All adsorption and calorimetry experiments were carried out at 298 K and at a fixed alcohol content (0.01 mol kg −1) either in deionized water or in a 0.01 mol kg −1 NaBr solution. Dilution calorimetry measurements allowed determination of the cumulative molar enthalpy changes and a new analysis of these data was proposed to calculate easily the enthalpy of micellization per mole of BDDAB, Δ mic h, and the CMC value. The alcohol addition was shown to render the micellization phenomenon more exothermic, the effect being larger as the chain length of alcohol increased. These effects were attributed to the location of alcohol molecules between the surfactant units, their hydroxyl groups close to the surfactant head-groups, in competition with the surfactant counterions. The individual isotherms of alcohol and surfactant adsorption onto XO15M and SiAl32 d 22 were determined. The plots of the pseudo-differential molar enthalpy of displacement, Δ dpl h, against the surface coverage by the surfactant cation, Θ BDDA+, were derived from the titration calorimetry data. The formation of surface-bound aggregates was thought to be a prerequisite for alcohol coadsorption at the solid–solution interface. At least two different types of adsolubilization sites were postulated, one of the sites being the same as in micelles and the other related to the contact area between the hydrophobic surfactant tails and the equilibrium bulk solution. Coadsorption (adsolubilization) of alcohol molecules at such sites was found to increase the exothermic contribution to the enthalpy of displacement per mole of the BDDA + adsorbed.

Controlled drug release from gels using surfactant aggregates. II. Vesicles formed from mixtures of amphiphilic drugs and oppositely charged surfactants.

The aim of this study was to control the release of charged drugs from gels by adding surfactants that can interact with the drug and polymer matrix. The in vitro release from gels was measured by using 6-mL gel holders immersed in 250 mL of simulated tear fluid and detecting the ultraviolet absorbance on-line. Gels were characterized by using a controlled rate rheometer, and surfactant aggregates were characterized by using cryo-transmission electron microscopy. The diffusion coefficient of alprenolol was 2.8 x 10(-6) cm2/s in a lipophilically modified poly(acrylic acid) gel without surfactants present and 0.14 x 10(-6) cm2/s when formulated with 1% sodium dodecyl sulfate. For fluvastatin, the diffusion coefficient changed from 3.0 x 10(-6) cm2/s to 0.07 x 10(-6) cm2/s in the presence of 0.2% benzyldimethyldodecyl-ammonium bromide. Alprenolol, betaxolol, metoprolol, diphenhydramine, and fluvastatin formed vesicles with oppositely charged surfactants in physiologic salt conditions. In this article we show that it is feasible to control the release of charged drugs from gels by using surfactants. Vesicles are generally formed when surface active drugs are mixed with oppositely charged surfactants in physiologic conditions. The strongest effects on the release rate are seen for lipophilically modified polymer gels in which the drug and the oppositely charged surfactant form vesicles, but systems with micelles also give a slower release.