Effects of solubilized dodecylamine on the microstructure of cetylpyridinium bromide-n-butanol-hexane-water system studied by pulsed-gradient spin echo NMR and ESR spin label methods

Abstract

The effect of solubilized dodecylamine (DDA) on the structure of the cetylpyridinium bromide-n-butanol-hexane-water microemulsions has been studied by the Fourier-transform pulsed-gradient spin-echo ~H nuclear magnetic resonance and the electron spin resonance spin label method. The sample compositions were chosen to examine three different microemulsion structures: oil-in-water, water-in-oil and bicontinuous. In all systems the DDA mo|ecules are shown to be incorporated into the oil-water interface, resulting in essential changes in the microemulsion structure. In the micellar systems the DDA emergence in the interface causes an increase of the micelle size and a redistribution of butanol and water between micelle and bulk phases. In the oil-in-water mir of amine-containing systems the quantity of micellized butanol and water decreases. In the water-in-oil microemulsions the introduction of DDA leads to an increase of butartol and water involved in the micelle formation. The redistribution of butanol and water between polar and organic phases in the microemulsions would be expected to cause changes in the bicontinuous structure.

Aminolysis of Carboxylic Acid Esters in Direct, Bicontinual, and Inverse Microemulsions Based on Cetyltrimethylammonium Bromide

“…In this case, we can distinguish in the plot the portions corresponding to the existence of inverse (j < 0.2), bicontinual (0.5 > j > 0.25), and direct (j > 0.6) microemulsions, which is consistent with the data from [8]. We have shown previously that introduction of long-chain amines into microemulsions based on cationic surfactants results in the redistribution of the components between the phases [15]. Changes in E T depending on the decylamine concentration (Fig.…”

Structural Characterization of Reconstituted Bioactive-Loaded Nanodomains after Embedding in Films Using Electron Paramagnetic Resonance and Self-Diffusion Nuclear Magnetic Resonance Techniques

“…Conversely, when the 5-DSA probe was inserted into the ME concentrate with no added water, microviscosity and order significantly increased (τ = 4.20 ns; S = 0.22), and micropolarity decreased (⟨ A ⟩ = 14.67 G). These parameters are characteristic of the insertion of the probe into ME droplets. , At the highest water contents (90 wt %), a decrease of microviscosity and order was obtained, but the micropolarity remained unchanged, indicating that ME droplets become more dynamic structures, as a result of complete water hydration of the surfactant heads. Therefore, the probe remains well embedded into these droplets as a cosurfactant .…”

“…These parameters are characteristic of the insertion of the probe into ME droplets. 30,37 At the highest water contents (90 wt %), a decrease of microviscosity and order was obtained, but the micropolarity remained unchanged, indicating that ME droplets become more dynamic structures, as a result of complete water hydration of the surfactant heads. Therefore, the probe remains well embedded into these droplets as a cosurfactant.…”

“…As described in the Experimental Section, the main parameters extracted from spectral computations are as follows: (a) the correlation time for the diffusional rotation motion of the probe, τ, that is, a “microviscosity parameter”, reporting on the interactions between the surfactant molecules, the environmental molecules, and the dynamics of the system at the probe site; (b) the order parameter S , which provides order information on the surfactant structure; , and (c) the coupling between the electron and the nitrogen nuclear spins, ⟨ A ⟩, which is a “micropolarity parameter”, reporting on the polarity variations at the probe environment. The microviscosity parameter, τ, and the order parameter S are shown in Figure for empty and curcumin-loaded MEs concentrates, 90 wt % water, 90 wt % water + gellan (1 wt %) mixture, film, and, finally, the dissolved film.…”

Mixed micellar systems of geminal alkylammonium surfactants and long-chain amines

“…20 On the basis of ESR spectra, one can judge not only about the mobility of spine labelled fragment of the probe and the polarity of its mi croenvironment, but also about the packing density of sur factant molecules inside the micelle. The quantity sen sible to the changes in this parameter is the isotropic hyperfine splitting constant (a N ) characterizing the inter action of the spin of the unpaired electron of the probe with the nuclear magnetic moment of the nitrogen atom.…”