Thermodynamics of Micelle Formation of Chlorhexidine Digluconate

Sarmiento, Félix; Rı́o, José Manuel del; Prieto, Gerardo; Attwood, David; Jones, M.N.; Mosquera, Vı́ctor

doi:10.1021/j100049a024

Cited by 48 publications

(41 citation statements)

References 8 publications

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“…We have previously examined the application of this model to systems of low aggregation number, including the cationic surfactant hexyltrimethylammonium bromide (10) and the amphiphilic drugs propranolol hydrochloride (11) and chlorhexidene digluconate (12). In each of these systems the enthalpies of micellization derived from the modified mass action treatment described below were in good agreement with experimental values from microcalorimetry.…”

Section: Thermodynamics Of Associationmentioning

confidence: 72%

Effect of Electrolyte on the Surface and Thermodynamic Properties of Amphiphilic Penicillins

Taboada

Attwood

Ruso

et al. 1999

Journal of Colloid and Interface Science

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Section: Thermodynamics Of Associationmentioning

confidence: 72%

Effect of Electrolyte on the Surface and Thermodynamic Properties of Amphiphilic Penicillins

Taboada

Attwood

Ruso

et al. 1999

Journal of Colloid and Interface Science

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“…Figure 2 shows plots of κ as a function of molal concentration of SPFO for different temperatures. For each temperature, the concentration dependence of the electrical conductivity shows a wide zone of transition from monomers to micelles, which is usual for weakly associating systems (34). The values of the CMC of the perfluorooctanoate were estimated from the intersection of two linear fragments above and below the breaks in the molality vs. conductivity plots for each temperature.…”

Section: Resultsmentioning

confidence: 99%

The self‐aggregation of sodium perfluorooctanoate in aqueous solution at different temperatures

González‐Pérez

Ruso

Prieto

et al. 2004

J Surfact & Detergents

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Electrical conductivities of sodium perfluorooctanoate (SPFO) in aqueous solutions were measured at different temperatures (range 293-328 K). Critical micelle concentrations (CMC) and the degree of ionization (α) of the micelles were derived from such data. The results revealed that temperature dependence of CMC is U-shaped with a minimum at 316 K. Gibbs free energies, enthalpies, and entropies of micelle formation as a function of temperature were estimated from the CMC and α values using the charged pseudo-phase separation model. To correlate the enthalpic and entropic contributions, the compensation phenomenon was studied, with a compensation temperature of 309 K and an intercept of −27.7 kJ⋅mol −1 . Apparent molar volumes and adiabatic compressibilities of SPFO were determined from density and ultrasound velocity measurements in the same temperature range as conductivities. Positive deviation from the Debye-Hückel limiting law of the apparent molar volume in the range of temperatures studied evidenced hydrogen bonding-type interactions between monomers and the existence of dimers in the premicellar region. With micellization, the apparent molar volumes decrease with rising temperature, indicating that the structure of micelles is looser than that of monomers. The isentropic apparent molar adiabatic compressibilities following micellization were positive, indicating the predominant role of the decrease in hydrophobic hydration in the association process.The substitution of hydrogen by fluorine produces dramatic changes in hydrogenated chains (1). The size of the fluorine atom (van der Waals radius ≈1.47 Å) (2) is significantly larger than the hydrogen atom (≈1.20 Å) (2), so perfluoroalkyl chains are bulkier than hydrogenated ones [with cross sections of ≈30 and ≈20 Å (2), respectively] (3,4). Owing to the low polarizability of fluorine (5), the van der Waals interactions between fluorinated chains are weak; consequently, the liquid fluorocarbons show low cohesive energy densities (6,7). This is reflected in very low surface tensions, high fluidities, low dielectric constants, high vapor pressures, high compressibilities, and high gas solubilities (8-10). Fluorinated amphiphiles have a greater tendency to self-assemble in water and to collect at interfaces than their hydrogenated analogs. For example, the incremental change in the free energy of adsorption for the transfer of a CF 2 group from water to the air/water interface is −5.1 kJ⋅mol −1 vs. −2.6 kJ⋅mol -1 for a CH 2 group (11,12). Fluorinated surfactants have lower critical micelle concentrations (CMC) than their hydrogenated counterparts. For instance, the contribution of a CF 2 group toward micellization of perfluorinated carboxylic acids is equivalent to 1.6 times that of a CH 2 group (13). Micelles of fluorinated amphiphiles tend to be rod-shaped, as predicted from calculations based on their geometry (3) and shown by experimental results (14,15). These specific characteristics of fluorinated surfactants are of special interest in a wide variety of a...

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“…The variation of the critical concentration (C*) of propranolol with temperature is shown in Fig. 2 and passes through a minimum of 295.4 K. This plot was fitted to the equation ln X C* ϭ aT 2 ϩ bT ϩ c, [2] where X C* is C* as a mole fraction. The values of the fitting constants were a ϭ (0.00087…”

Section: Critical Concentration and Counterion Bindingmentioning

confidence: 99%

“…In our continuing investigations on the association characteristics and surface properties of a wide variety of drugs (1)(2)(3)(4)(5) we have investigated propranolol hydrochloride (I), which is the prototype of the beta-adrenergic blocking agents. It is a racemic compound, with only its 1-isomer having any adrenergic blocking activity.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics of Micellization of Surfactants of Low Aggregation Number: The Aggregation of Propranolol Hydrochloride

Mosquera

Ruso

Attwood

et al. 1999

Journal of Colloid and Interface Science

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Thermodynamics of Micelle Formation of Chlorhexidine Digluconate

Cited by 48 publications

References 8 publications

Effect of Electrolyte on the Surface and Thermodynamic Properties of Amphiphilic Penicillins

Effect of Electrolyte on the Surface and Thermodynamic Properties of Amphiphilic Penicillins

The self‐aggregation of sodium perfluorooctanoate in aqueous solution at different temperatures

Thermodynamics of Micellization of Surfactants of Low Aggregation Number: The Aggregation of Propranolol Hydrochloride

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