Physicochemical Behaviors of Cationic Gemini Surfactant (14-4-14) Based Microheterogeneous Assemblies

Abstract

A comprehensive study of micellization and microemulsion formation of a cationic gemini surfactant (tetramethylene-1,4-bis(dimethyltetradecylammonium bromide; 14-4-14) in the absence or presence of hydrophobically modified polyelectrolyte, sodium carboxymethylcellulose (NaCMC), has been conducted by conductometry, tensiometry, microcalorimetry, and fluorimetry methods at different temperatures. Both critical micelle concentration and degree of ionization of the surfactant have been observed to increase with increasing temperature. The interfacial and thermodynamic parameters were evaluated. The standard Gibbs free energy of micellization (ΔGm°) is negative, which decreases with increase in temperature. Larger entropic contribution is observed compared to the enthalpy. The interaction of 14-4-14 with NaCMC produces coacervates which was determined from turbidimetry method. The pseudoternary phase behavior of the microemulsion systems comprising water (or NaCMC as additive), 14-4-14, isopropanol (IP) or n-butanol (Bu) as cosurfactant, and isopropyl myristate (IPM) were studied at 298 K. Phase diagrams reveal that IP derived microemulsions (in the absence of NaCMC) offer a large isotropic region compared to Bu-derived systems at comparable physicochemical conditions. Increasing the concentration of IP or Bu decreases the isotropic region in the phase diagram. NaCMC influences the microemulsion zone, depending upon its concentration, and type of cosurfactant and surfantant/cosurfactant ratio. Dynamic light scattering and conductometric measurements show the size of the droplet, threshold temperature of percolation, scaling parameters, and activation energy of the percolation process of 14-4-14/IP or Bu derived microemulsion systems without/with NaCMC at various physicochemical conditions. Bu exerts a greater effect to reduce θt than IP as a cosurfactant (in the absence of NaCMC) at comparable ω. On the other hand, IP showed better percolating effect than Bu in the presence of NaCMC. Bu and IP (as cosurfactant) and NaCMC (as additive) influenced the microemulsion droplet size (Dh) to different extents under comparable conditions. Temperature insensitive microemulsions have been reported at the studied temperature range (298–353 K). 14-4-14/IP (1:2)-derived microemulsion showed a fractured surface at fixed ω = 15, where ω is the water and surfactant molar ratio, and temperature (298 K); whereas, large scale mesospheres comprising multiple closely winded nanoslices and spheroid morphology were formed in 14-4-14/IP and 14-4-14/Bu microemulsions, respectively, in the presence of 0.01 g % NaCMC, at comparable conditions. These systems revealed good antimicrobial activity toward the strains of Gram-positive Bacillus subtilis and Gram-negative Escherichia coli bacteria at 298 K, and inhibitory effect was governed by ω, type of cosurfactant, and bacterial strains.

Formation of Oil/Water Interface by Mixed Surface Active Ionic Liquid-Ethoxylated Alkyl Ether: Energetics, Microstructures, Solvation Dynamics, and Antimicrobial Activity

“…The less polar dispersion at lower water content makes surfactant easier to accumulate on the cell membrane to disrupt it . Similar results were obtained for a cationic Gemini surfactant based microemulsion systems . Hence, the reported w/o microemulsions at mixed surfactant composition could be prospective for using with good standing of antimicrobial property.…”

Drug‐Induced Micelle‐to‐Vesicle Transition of a Cationic Gemini Surfactant: Potential Applications in Drug Delivery

“…[35][36][37][38][39][40] GSs have attracted much attention because of their superiorp roperties compared to single-chain surfactants, such as low criticalm icelle concentration (cmc), highsurface activity,l ow Kraft temperature, unusual rheological properties, antimicrobial activity,a nd better wettability and foaming. [41][42][43][44] These interesting properties can be manipulated by changingt he length of the hydrophobic tails and the spacer. For example, the following physicochemical properties of aqueous solutions of GSs show non-monotonous dependence on the length of the spacer:t he molecular area at the water/ air interface, the cmc, the morphology of the micellar aggregate, the phase behavior,a nd the rheology.M ost of these unexpecteds olution properties were observedf or GSs with the same surfactant tail as employedi nt he present study,n amely, C 12 H 25 .…”

Supramolecular aggregates from polyacrylates and Gd(iii)-containing cationic surfactants as high-relaxivity MRI contrast agents

“…22,25 Counterions of both the polyion and the charged micelles are largely expelled from the complex, such that the binding of oppositely charged surfactants to polyelectrolytes can be, to a first approximation, visualized as 15 an ion-exchange process where "condensed" counterions are replaced by surfactants. Scheme 1 illustrates the aggregate behavior in these PSC systems, similar with the physicochemical behaviors of cationic gemini surfactant investigated by Ghosh et al 43 The relaxivities of the PSCs were obtained by measuring the longitudinal (T 1 ) relaxation times of the samples on a GE SIGNA 35 EXCITE 1.5T MRI Scanner at several different concentrations (based on Gd(III)). The relaxivity values (r 1 ) were measured over CAC, calculated from the slope of the plot of 1/T 1 vs concentration of Gd (III).…”