Tetradecyldimethylammonium Bromide Research Articles

Drug induced catanionic vesicles assisted fabrication of hollow silica nano-spheres as the new age chemo-drug carrier

Surfactant vesicles have elicited the attention because of their non-toxic nature, ease of preparation, low cost programmable drug delivery vehicle and soft templates for the organized nano-assemblies. To unleash their potential as the new age drug carrier, herein we have designed catanionic vesicles formed through synergistic interactions between the hydrotropic drug diclofenac sodium (DS) and cationic gemini surfactants (GS) with varying alkyl chain lengths i.e. hexamethylene 1,6-bis (tetradecyl dimethyl ammonium bromide); and hexamethylene 1,6-bis (hexadecyl dimethyl ammonium bromide). The prepared catanionic vesicles were then used as the soft templates to synthesize hollow silica nano spheres with 62 nm size and 0.86 cm3/g pore volume to accommodate the anti-cancer drug imatinib mesylate. Results of encapsulation and release demonstrate that the studied system could potentially serve as a stable nano-delivery system for delivering the hydrophobic drugs in the future.

Dimethylenebis-(tetra-decyldimethylammonium Bromide)-Driven Au Nanoparticles: Hg2+ Sensing a Competency

Heavy metal ions can cause severe threats to the environment and human health, and the potential sources of substantial metal ions are mining, agriculture, toxic wastes, electronic merchandise, and natural discharge from earth’s crust into the surroundings. This discharge from oceanic and volcanic emissions end up in the contamination of underground water resources and human beings get exposed to the same. Among aforesaid ions, mercury ions are incredibly fatal and may cause serious health problems if consumed by individuals, leading to numerous critical diseases such as harmful effects on immune systems, cancer, organ damage, nervous system damage, etc.In order to confirm these, it is essential to investigate the influence of the shorter hydrocarbon chain length on the detection performance of metal nanoparticles. In view of that, we selected dimethylenebis-(tetra-decyldimethylammonium bromide) (14–2-14) GS with a shorter hydrocarbon chain length and further investigated sensitivity and selectivity of anisotropic nanoparticles.

Mixed micellization behavior of benzyldimethylhexadecylammonium chloride with gemini surfactants and their applications in the synthesis of silver nanoparticles

Aggregation and adsorption properties of benzyldimethylhexadecylammonium chloride (BDHAC) with three cationic alkanediyl-1,s-bis(tetradecyldimethyl-ammonium bromide) gemini surfactants, viz. butanediyl-1,4-bis(tetradecyldimethylammonium bromide), pentanediyl-1,5-bis(tetradecyldimethylammonium bromide) and hexanediyl-1,6-bis(tetradecyldimethylammonium bromide) respectively referred to as 14-4-14, 14-5-14 and 14-6-14 (in general 14-s-14, where s = 4, 5, 6) have been studied by tensiometric, conductometric, fluorimetric and dynamic light scattering experimental methods at 298.15 K. The studies were conducted at various compositions of the mixed systems ranging between 0 and 1. The parameters determined include different physicochemical and interaction parameters. The negative values of interaction parameters obtained for mixed micelle formation point out the attractive interaction among the components and lead to non-ideality which has been theoretically treated by Clint’s and Rubingh’s models. The BDHAC + 14-s-14 mixtures in different mole fractions were used in the synthesis of very stable silver nanoparticles (Ag NPs) in aqueous media, which were characterized by UV-visible spectroscopy. Dynamic light scattering measurements revealed that the size of micelles as well as Ag NPs increases with the increase in mole fraction of BDHAC in the mixtures and the size of Ag NPs can be very much controlled by using mixtures of surfactants.

Dimethylenebis-(tetra-decyldimethylammonium Bromide)-Driven Metal Nanoparticles: Hg2+ Sensing a Competency.

We report an excellent anisotropic Au nanoparticle-based colorimetric probe for the detection of Hg2+ ions with higher detection ability and selectivity. The manifestation of different morphologies of Au nanoparticles including round, triangular, rectangular, pentagonal, and hexagonal has been realized by the dimethylenebis-(tetra-decyldimethylammonium bromide) (14-2-14 Gemini surfactant) assisted one-step thermal reduction method where the average size of Au nanoparticles was 54.65 ± 44.3 nm. The growth and frequency of Au nanoparticles were enhanced as a function of Gemini surfactant’s concentration. The detection limit as low as 1.8 nM was efficaciously achieved and was considerably lower than the required world standards defined the maximum allowable level of Hg2+ ions for health hazards. Notably, the Au nanoparticles showed visible detection for 100 μM Hg2+ ion by means of the change in the solution color from red to tarnish blue within 180 s followed by saturation in the absorption ratio (ALSPR/ATSPR). These results provide novel insight into the detection of the heavy metal ion using Gemini surfactant-assisted grown anisotropic metal nanoparticles. On the basis of obtained results, it is concluded that the size of metal nanoparticles is no longer critical for preparation of efficient selective chemoprobe; rather, growth of more number of edges provides a large number of sights for incoming moieties and plays an important role in improving the detection capability of the anisotropic metal nanoparticle irrespective of their large sizes. We believe that this work provides valuable insight into researchers working in the area of chemosensor applications.

Aggregation behaviour of tetracaine hydrochloride with Gemini surfactants and the formation of silver nanoparticles using drug-Gemini surfactants mixture

This study aimed to encapsulate drug into the silver nanoparticles (AgNPs) by using drug-Gemini surfactant mixed aggregate. The applicability of drug-surfactant based AgNPs is to carry the maximum amount of drug during the drug delivery process. The nano-size mixed aggregate was prepared by a local anaesthetic amphiphilic drug, tetracaine hydrochloride (TC) and Gemini surfactants, pentamethylene-1, 5-bis(tetradecyldimethylammonium bromide) (GS-5, 14-5-14) and hexamethylene-1,6-bis(tetradecyldimethylammonium bromide) (GS-6, 14-6-14). Surface tension and conductance measurements were used to determine the physiological and thermodynamic interaction parameters of TC-GS-5/GS-6. The negative βm values suggested as the synergistic interactions observed between TC and GS-5/GS-6 mixed aggregate. The TC-GSs mixture was used to stabilizing silver nanoparticles (AgNPs) with a different mole fraction αTC 0.0–0.99 in aqueous media. The resulting AgNPs characterized by UV–Vis spectroscopy and transmission electron microscopy (TEM). Dynamic light scattering (DLS) suggested that the different types of aggregate formed in aqueous media depending on the internal packing arrangements of TC-GS-5/GS-6. The mole fraction base formulation of drug-surfactant could control the mixed aggregates which could be used to formed drug-surfactant based nanoparticles to enhance the performance of drug delivery.

A Mathematical Approach to a More Accurate Determination of Critical Micelle Concentration and Other Thermodynamic Parameters of 14‐2‐14 Gemini Surfactant in Water–Organic Solvent Mixed Media at Variable Temperatures

AbstractTo explore how the solvent characteristics influence the self‐aggregation of the cationic gemini surfactant dimethylene‐1,2‐bis(tetradecyldimethylammonium bromide) (14‐2‐14) and to obtain various energetic parameters, conductometric experiments were performed on the binary mixtures in the presence of commonly used organic solvents; formamide (FA), acetonitrile (AN) and 2‐methoxyethanol (ME) in aqueous solutions at varying temperatures (298.15–323.15 K) and compositions. The procedure suggested by Carpena et al. has been utilized to analyze conductivity–concentration plots in order to obtain critical micelle concentration (CMC) and degree of counterion dissociation (α) of the micelles. This method provides more accurate results as compared to conventional treatments, and the experimental error for the evaluation of micellar parameters is reduced significantly. The results revealed that, although the process of micellization becomes less favorable with the increase in composition of FA, AN and ME in mixed systems, the increase in CMC at compositions lower than 20% (v/v) of the organic solvents is relatively less, indicating that water character is dominant in the bulk phase. As the enthalpy of micellization became more negative, the corresponding entropy change became less positive and enthalpy–entropy compensation phenomenon has been observed for 14‐2‐14 in all the mixtures within the studied temperature range.

Effect of ethylene glycol and propylene glycol on the aggregation of alkanediyl-α,ω-bis(tetradecyldimethylammonium bromide) (14–s–14; s = 4–6) gemini surfactants

The effect of addition of two co-solvents (ethylene glycol (EG) and propylene glycol (PG)) on the aggregation properties of three cationic gemini surfactants (viz. butanediyl-1,4-bis(tetradecyldimethylammonium bromide) (14–4–14), pentanediyl-1,5-bis(tetradecyldimethylammonium bromide) (14–5–14) and hexanediyl-1,6-bis(tetradecyldimethylammonium bromide) (14–6–14)) has been studied by conductance, steady state fluorescence and dynamic light scattering measurements at 298K. The weight percentage of these co-solvents varied in between 0 and 50% at an interval of 5% up to 20% and then 10% up to 50%. Micellization is delayed by the addition of co-solvents; consequently, a progressive increase was observed in critical micelle concentration (cmc) and Gibbs free energy of micellization (ΔGm0), a rough increase was observed in the values of degree of counter ion dissociation (α) and a decrease was obtained in values of average aggregation number (Nagg) and Stern–Volmer constant (KSV). At low weight percentage (up to 15%) of co-solvents, 14–s–14 (s=4–6) geminis are found to be almost equally prone to micellization both in EG–water (EG–WR) and in PG–water (PG–WR) mixed media whereas at high weight percentages they are more prone to micellization in EG–WR than in PG–WR mixed media. The measurements of hydrodynamic radius (dH) performed at a concentration of 10mmolkg−1 shows that the hydrodynamic diameter (dH) is less than 70nm for most of the system except at some of the composition where slightly higher values were obtained.

The influence of the micellar pseudophase of the double-chained cationic surfactant di-n-tetradecyldimethylammonium bromide on the absorption spectra and protolytic equilibrium of indicator dyes

Abstract The absorption spectra and protolytic equilibrium of a set of acid–base indicators and solvatochromic dyes have been studied in aqueous solutions of the cationic surfactants possessing two long hydrocarbon tails. In water, the double-chained surfactant di- n -tetradecyldimethylammonium bromide, DTDAB, forms large-sized anisometric self-assembled aggregates or bilayer (vesicle) type. The anionic dyes are readily bound to the DTDAB pseudophase, which results in the pronounced shifts of their absorption bands and alterations of the p K a s. The results have been compared with those obtained earlier in CTAB and gemini 16-4-16 cationic surfactants.

Micellization and Surface Properties of Alkanediyl-1,4-bis(tetradecyldimethylammonium Bromide) Gemini Surfactants with Dodecylethyldimethylammonium Bromide

Mixed micellization and surface properties of three cationic gemini surfactants, viz., (butanediyl-), (pentanediyl-), (hexanediyl-)-1,4-bis(tetradecyldimethylammonium bromide) (14-s-14; s = 4–6) with dodecylethyldimethylammonium bromide have been studied by conductometric, tensiometric, and fluorimetric techniques at 298 K. Values of cmc, ideal cmc(cmc*), degree of counter ion dissociation (g), micellar mole fractions of the components, and interaction parameters have been determined. Further, activity coefficients of the components, surface excess concentration (Γmax), minimum surface area per molecule (Amin), surface pressure at the cmc (πcmc), average aggregation numbers of the micelles (Nagg), excess Gibbs free energy (), and Gibbs free energy of micellization () were also calculated and discussed. The compositions of the mixed systems were varied between 0 and 1. It is observed that the values of cmc, g, , , and Γmax decreases whereas Amin increases with augmentation of 14-s-14 (s = 4–6) mole fraction in the mixed systems. The negative values of interaction parameters (βσ and βm) obtained for mixed micelle formation indicate attractive interaction between the components leading to nonideality. The nonideal behavior has been theoretically treated by Clint's and Rubingh's model in light of regular solution theory.

Study of the interactions in dicationic gemini–anionic conventional mixed surfactant systems in the viewpoint of regular solution theory

In the present study, the influence of the hydrocarbon chain length of gemini surfactants on the process of micellization in mixed surfactant systems was investigated. Experiments were carried out with alkyldiyl-α, ω-bis(tetradecyldimethylammonium bromide) (m-4-m) dicationic gemini (m=14, 16)/anionic sodium dodecylbenzene sulfonate (SDBS) mixed surfactant systems in different ratios. The critical micelle concentration (cmc) values of binary mixtures of surfactants were evaluated using surface tension measurements. Results showed that mixtures of the SDBS with gemini surfactants possessed significant deviations from ideal behavior (attractive interactions). The application of the regular solution theory (RST) to experimental data yielded the interaction parameter at mixed micelles (β) and air–water interface (βσ), indicating an attractive interaction and reflecting the synergistic behavior in both the systems. The experimental mole fraction (X1) was found to be lower than the ideal mole fraction (X1ideal), the mole fractions of SDBS for both systems, provided that mixed micelles were more occupied by SDBS. In addition, the micelle aggregation number (Nagg) increased with an increase in the length of the hydrophobic tail. The micropolarity and binding constant (Ksv) values of various combinations were determined from the ratio of intensity (I1/I3) of peaks of pyrene fluorescence emission spectrum and its quenching.

Self-Aggregation of Cationic Dimeric and Anionic Monomeric Surfactants with Nonionic Surfactant in Aqueous Medium

Spectrofluorometric measurements have been used to elaborate the self-aggregation of mixture of anioinic, sodium dodecylbenzenesulfonate (SDBS), and cationic gemini, alkanediyl-α, ω-bis (tetradecyldimethylammonium bromide) (14-4-14) with nonionic surfactant, polyoxyethylene 10 cetyl ether (Brij-56). The critical micelle concentration (cmc) of the binary mixtures has been investigated. Application of the regular solution theory (RST) to the experimental data yield the interaction parameter at mixed micelles (β), indicate an attractive interaction and reflect the synergistic behavior in both Brij-56/SDBS and Brij-56/14-4-14 systems. The micelle aggregation number (N agg) was measured using a steady state fluorescence quenching method. The N agg values of the mixed surfactant system were larger than those of pure components. The micropolarity of various combinations and the binding constants (K sv) were determined from the ratio of intensity of peaks (I 1/I 3) of pyrene fluorescence emission spectrum and its quenching, respectively.

Surface adsorption and mixed micelle formation of surface active ionic liquid in cationic surfactants: Conductivity, surface tension, fluorescence and NMR studies

Here we are reporting the influence of 1-tetradecyl-3-methylimidazolium bromide (C14mimBr), a surface-active ionic liquid (SAIL) on the micellar morphological changes of cationic surfactants such as tetradecyltrimethylammonium bromide (TTAB), dimethylditetradecylammonium bromide (DTDAB), alkane-bis (tetradecyldimethylammonium bromide) (14-2-14 and 14-4-14 gemini). The techniques employed were conductivity, surface tension, fluorescence and 1H NMR. The various micellar and interfacial parameters such as critical micelle concentration (cmc), degree of counterion binding (g), interaction parameter (βm), surface excess concentration (Гmax), minimum area per molecule (Amin), aggregation number (Nagg), Stern–Volmer constant (Ksv) as well as some thermodynamic parameters such as standard Gibbs free energy of adsorption (ΔGads0), excess free energy of micellization (ΔGex) and standard Gibbs free energy of micellization (ΔGm0) have been evaluated. The interactions for IL+ TTAB mixtures are found to be non-ideal and antagonistic. However when the single chain surfactant is replaced by the double chain surfactants the interactions becomes synergistic for the mixtures. The merging and broadening of the peaks for various protons of IL and cationic surfactants suggests the growth of micelles. On comparison between the binary mixtures of IL+ 14-2-14 and IL+ 14-4-14, former one with more hydrophilic spacer promote micellization more easily than 14-4-14.

Micellization and Thermodynamic Parameters of Butanediyl-1,4-bis(tetradecyldimethylammonium Bromide) Gemini Surfactant at Different Temperatures: Effect of the Addition of 2-Methoxyethanol

The effect of the addition of 2-methoxyethanol on the critical micelle concentration (cmc) and on the degree of counterion dissociation (α) of butanediyl-1,4-bis(tetradecyldimethylammonium bromide) gemini surfactant, [C14H29N+(CH3)2–(CH2)4–N+(CH3)2C14H29,2Br−] (referred as 14–4–14,2Br−), has been studied by varying the compositions of the 2-methoxyethanol + water mixed solvent media (0 to 50 %). To determine various thermodynamic parameters of micellization, on the basis of the mass–action model for micelle formation, the experiments were performed at selected compositions of the mixed solvent at four temperatures ranging between 25 °C and 50 °C. Furthermore, the air/bulk surface tensions of the pure and mixed media were determined, and a successful attempt was made to correlate the cohesive energy density described through the Gordon parameter with the values of Gibbs energy of micellization.

Fluorescence spectroscopic studies on the interaction of Gemini surfactant 14‐6‐14 with bovine serum albumin

The interaction of the cationic Gemini surfactant hexamethylene-1,3-bis (tetradecyldimethylammonium bromide) (14-6-14) with bovine serum albumin (BSA) has been investigated by fluorescence quenching spectra and three-dimensional (3D) fluorescence spectra. The Stern-Volmer quenching constants K(SV) and the corresponding thermodynamic parameters ΔH, ΔG and ΔS have been estimated by the fluorescence quenching method. The results indicated that hydrophobic forces were the predominant intermolecular forces between BSA and the surfactant. Competitive experiments and the number of binding sites calculation show that 14-6-14 can be inserted in site-II (in subdomain IIIA) of BSA. The effect of 14-6-14 on the conformation of BSA was evaluated by synchronous fluorescence spectroscopy and 3D fluorescence spectral methods. The results show that the conformation of BSA was changed dramatically in the presence of 14-6-14, by binding to the Trp and Try residues of BSA. The investigation provides interaction between BSA and 14-6-14 as a model for molecular design and industrial research.

Studies on the Effect of Organic Solvents and Temperature on the Micellar Solution of Pentamethylene-1,5-bis(tetradecyldimethylammonium bromide) Gemini Surfactant

Effects of three organic solvents, viz. methyl cellosolve, acetonitrile, and formamide, on the micellization process of Gemini surfactant pentamethylene-1,5-bis(tetradecyldimethylammonium bromide) aqueous solutions, with the volume percentages of the organic solvents up to 50%, have been investigated conductometrically. The studies were made at different temperatures and the data were used to find out different micellization parameters. From the study, it was observed that, although an increment in the amount of the organic solvents delays the micellization, the increase in the critical micelle concentration (cmc) is comparatively less below 20%(v/v) showing the predominance of water character in the bulk phase at lower compositions of the organic solvents. Applying equilibrium model for micelle formation, various thermodynamic parameters were also calculated from the temperature dependence of the cmc values and the results show that the micellization process becomes less spontaneous as the volume % of the organic solvent increases in the system due to the action of water-organic solvent mixed media as better solvent than pure water (solvophobic effect) for the studied Gemini molecules.

Properties of binary surfactant systems of nonionic surfactants C 12E 10, C 12E 23, and C 12E 42 with a cationic gemini surfactant in aqueous solutions

Properties of binary surfactant systems of nonionic surfactants poly(ethylene oxide) (PEO) lauryl ethers (C 12E 10, C 12E 23, C 12E 42) with a cationic gemini surfactant, butanediyl-α,ω-bis(tetradecyldimethylammonium bromide) (14-4-14), have been investigated by Steady-state Fluorescence (FL), zeta potential, Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM), Cryogenic Transmission Electron Microscopy (CryoTEM), and X-ray Diffraction (XRD). Through FL measurements, critical micelle concentration (CMC) of the three binary systems for different mixing mole fractions is determined and the values fall between those of pure constituent surfactants. Ideal CMC (CMC ideal), mole fraction in aggregates ( X), interaction parameter ( β), activity coefficients ( f 1 and f 2), and excess free energy of mixing (Δ G ex) have been calculated. All these parameters indicate nonideal behavior and synergistic interactions between the constituent surfactants, which is explained in terms of electrostatic attraction between headgroups of constituent surfactants and reduction of electrostatic repulsion between headgroups of 14-4-14 due to the presence of nonionic surfactants. DLS, TEM and CryoTEM results show that nonionic surfactants facilitate the formation of larger aggregates. Micelles and vesicles in larger size compared with those of 14-4-14 coexist in the mixed solutions. Both surfactant composition and PEO chain length are found to play a strong effect on the properties of the binary systems.

Gemini surfactant dimethylene-1,2-bis(tetradecyldimethylammonium bromide)-based gene vectors: A biophysical approach to transfection efficiency

Cationic liposomes have been proposed as biocompatible gene delivery vectors, able to overcome the barriers imposed by cell membranes. Besides lipids, other surfactant molecules have been successfully used in the composition of gene carriers. In the present work, we used a Gemini surfactant, represented by the general structure [C14H29(CH3)2N+(CH2)2N+(CH3)2C14H29]2Br− and herein designated 14–2–14, to prepare cationic gene carriers, both as the sole component and in combination with neutral helper lipids, cholesterol and DOPE. The effectiveness of three Gemini-based formulations, namely neat 14–2–14, 14–2–14:Chol (1:1 molar ratio) and 14–2–14:Chol:DOPE (2:1:1 molar ratio), to mediate gene delivery was evaluated in DNA mixtures of +/− charge ratios ranging from 1/1 to 12/1. After ruling out cytotoxicity as responsible for the differences observed in the transfection competence, structural and physical properties of the vector were investigated, using several techniques. The size and surface charge density (zeta potential) of surfactant-based structures were determined by conventional techniques and the thermotropic behaviour of aqueous dispersions of surfactant/lipid/DNA formulations was monitored by fluorescence polarization of DPH and DPH-PA probes. The capacity of lipoplexes to interact with membrane-mimicking lipid bilayers was evaluated, using the PicoGreen assay and a FRET technique. Our data indicate inefficiency of the neat 14–2–14 formulation for gene delivery, which could result from the large dimensions of the particles and/or from its relative incompetence to release DNA upon interaction with anionic lipids. The addition of cholesterol or cholesterol and DOPE conferred to Gemini-based gene carrier transfection activity at specific ranges of +/− charge ratios. Fluorescence polarization data suggest that an order parameter within a specific range was apparently needed for complexes to display maximal transfection efficiency. The transfection-competent formulations showed to be efficiently destabilized by interaction with different anionic and zwitterionic bilayers, including those containing PS and cardiolipin. These data are discussed in terms of the potential of these formulations to address different intracellular targets.

Conductometric and Fluorimetric Investigations on the Properties of Mixed Micelles of Two Cationic Gemini Surfactants

The mixed micellar properties of two cationic gemini surfactants, alkanediyl-α,ω-bis(tetradecyldimethylammonium bromide) and alkanediyl-α,ω-bis(hexadecyldimethylammonium bromide), 14-s-14 and 16-s-16, in aqueous solution have been investigated by conductivity and fluorescence techniques. The conductivity method has been carried out to evaluate critical micelle concentration (c), degree of counterion binding (g), and other related parameters like ideal mixed critical micelle concentration (c*), micellar mole fraction (x), interaction parameter (β) from Rubingh’s model, and xideal from Motomura’s model. Activity coefficients (f1 and f2) and Gibbs excess energy (GE) were also calculated. Fluorescence measurements were used to obtain the values of Nagg and Stern−Volmer constant (Ksv). The results suggest synergism in the system. The β values are negative, and their magnitudes increase with increasing spacer chain lengths. x1 > x1ideal values suggest that the contribution of the 14-s-14 component is greater as compared to that in the ideal state.

Aggregation Behavior of Amphiphilic Dendritic Block Copolymer with Butanediyl-α,ω-bis(tetradecyldimethylammonium bromide) in Aqueous Solution

Aggregation behavior of an amphiphilic dendritic block copolymer, a generation 1.0 poly(amidoamine) (G1.0 PAMAM) dendrimer based poly(propylene oxide) (PPO)-block-poly(ethylene oxide) (PEO) copolymer that was abbreviated as PPP, with a cationic gemini surfactant butanediyl-α,ω-bis(tetradecyldimethylammonium bromide) (14-4-14) in aqueous solution was investigated by the measurements of steady-state fluorescence (FL), cloud point (CP), transmission electron microscope (TEM), and dynamic light scattering (DLS). Through FL method, the critical aggregation concentration (CAC) of PPP in the absence and presence of 14-4-14 was determined. As the concentration of 14-4-14 increases, CAC values increase, suggesting the participation of copolymer−surfactant complexes in aggregate formation. The CP temperature of PPP increases as the content of 14-4-14 increases in the mixed system, which indicates that 14-4-14 increases the solubility of PPP. From TEM and DLS, the morphology and size distribution of the aggregates were obtained. The spherical aggregates are found to be larger in size and narrower in distribution with the addition of 14-4-14, which confirms further the formation of mixed aggregates. All of the above are explained on the basis of strong interactions between PPP and 14-4-14. Through hydrophobic interactions, 14-4-14 molecules can associate with PPP molecules to form copolymer−surfactant complexes that can aggregate further.

Effects of Solvent Media and Temperature on the Self-Aggregation of Cationic Dimeric Surfactant 14−6−14, 2Br− Studied by Conductometric and Fluorescence Techniques

To explore how the solvent characteristics influence the self-aggregation of the cationic dimeric surfactant hexamethylene-1,6-bis(tetradecyldimethylammonium bromide) (14-6-14, 2Br(-)) and to obtain various energetic parameters, conductometric experiments were performed on the binary mixtures of three organic solvents--viz., 2-methoxyethanol (ME)-, acetonitrile (AN)-, and formamide (FA)- water (WR) at different temperatures ranging from 298.15 to 323.15 K. The steady state fluorescence measurements allowed us to calculate the average aggregation number (N(agg)) and the air-bulk phase surface tension helped us to correlate the solvent cohesive energy density with Gibbs energy of micellization (DeltaG(0)(m)). The results showed that, although micellization process becomes less favorable with the increase in volume % of the ME, AN and FA in the binary mixed media, the increment in the cmc below 20% (v/v) of the organic solvents is comparatively less showing the predominance of WR character in the bulk phase. Because of the decrease in Gibbs interfacial energy contribution (DeltaG(0)(interf)) to DeltaG(0)(m), the average aggregation number (N(agg)) decreased with the increase in the volume % of the organic solvent in the mixed media. As the enthalpy of micellization became more negative, the corresponding entropy change became less positive and enthalpy-entropy compensation phenomenon was observed for the micellization of 14-6-14, 2Br(-) in all the mixed media in the studied temperature range.