Thermodynamics of Micellar Systems: Volumes and Heat Capacities of Alkyldimethylamine Oxides in Water

Desnoyers, Jacques E.; Roberts, David W.; DeLisi, R.; Perron, Gérald

doi:10.1007/978-1-4613-3491-0_17

Cited by 11 publications

(4 citation statements)

References 19 publications

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“…Desnoyers et al reported cmc values in the range from 14 to 21 mM and Δ mic h values of ca. 13 kJ·mol -1 . , However, the liquid flow calorimetric method they used provided less accurate results for C 10 DAO than for the lower homologue members of the alkyldimethylamine oxide series studied. The present results can further be compared with cmc = 20 mM and Δ mic h = 11.3 kJ·mol -1 obtained from heat of solution measurements by Benjamin .…”

Section: Resultsmentioning

confidence: 96%

Calorimetric Study of the Adsorption of Short-Chain Nonionic Surfactants on Silica Glass and Graphite: Dimethyldecylamine Oxide and Octyl Monoglucoside

Király

Findenegg

2000

Langmuir

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The material and enthalpy balances of adsorption of the nonionic surfactants N,N-dimethyldecylamine-N-oxide (C10DAO) and n-octyl β-d-monoglucoside (C8G1) from dilute aqueous solutions onto hydrophilic silica glass and hydrophobic graphite (graphitized carbon black) were determined at 298.15 K up to the critical micelle concentration. An automated flow sorption/microcalorimeter system was used for simultaneous measurements of the adsorption isotherm and the enthalpy isotherm of displacement. The formation of the adsorption layer is discussed in terms of the differential molar enthalpy data of adsorption as a function of surface coverage, and the results are related to the aggregated structure of nonionic surfactants at silica/solution and graphite/solution interfaces studied by atomic force microscopy. On silica, a low-density adsorption region (exothermic) is followed by a high-density adsorption region to produce globular surface aggregates of both C8G1 and C10DAO. On graphite, the formation of a flat, ordered monolayer (exothermic) is followed by the formation of C8G1 surface hemicylinders or, probably, a flat, less ordered bilayer of C10DAO. In either case, the adsorption in the high-density adsorbate region is endothermic, like micelle formation in aqueous bulk solution, as is to be expected on the basis of current models of surface aggregation of nonionic surfactants on hydrophilic and hydrophobic surfaces.

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Section: Resultsmentioning

confidence: 96%

Calorimetric Study of the Adsorption of Short-Chain Nonionic Surfactants on Silica Glass and Graphite: Dimethyldecylamine Oxide and Octyl Monoglucoside

Király

Findenegg

2000

Langmuir

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“…Octyl- and decyldimethylaminoxides were prepared and purified as described by Desnoyers et al Hydrogen peroxide was neutralized by adding the proper amount on manganese dioxide MnO 2 and filtered with a Supelco 0.45-μm filter of nylon-6,6. Then, the aminoxides were obtained following three azeotropic distillations with 2-propanol and recrystallization in acetone.…”

Section: Methodsmentioning

confidence: 99%

Apparent Molar Volumes and Heat Capacities of Various Adsorbed Additives on Polystyrene Latexes

2002

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Flow densimetry and flow microcalorimetry have been used to study the effect of electrolytes, surfactants, and alcohols on positively and negatively charged polystyrene latexes. The thermodynamic volumes and heat capacities of transfer of the latex from water to the aqueous solutions and of the additives from water to the latex dispersions were measured as a function of the additive concentration. With some systems, the adsorption isotherms were also determined. These thermodynamic properties are largely insensitive to electrostatic interactions but depend significantly on changes in hydrophobic interactions resulting from adsorption of the additive on the latex. Negligible changes in the quantities of transfer are thus observed for electrolytes, methoxyethanol, and methanol, but ionic and nonionic surfactants are adsorbed on both types of latexes. The adsorption of medium-chain-length alcohols and alkoxyethanols increases with their hydrophobic character. A simple model based on the Langmuir isotherm, the thermodynamic properties of the additives in water, and the properties of the adsorbed additives correctly predicts the general trends of the transfer functions of the additive and of the latex. However, a detailed analysis of the data indicates that the adsorption isotherm is more complex than expected from the Langmuir equation and that the thermodynamic properties of the adsorbed species depend on the extent of coverage. At high concentrations, the volumes and heat capacities of adsorbed surfactants are of the same order of magnitude as the corresponding values of the surfactants in micellar form.

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“…The adsorption in Figure is enthalpically driven over the whole molality range studied. Despite the short chain length of C8DAO, it is a typical nonionic surfactant . Due to surface heterogeneity of silica gel, the high-energy sites are occupied first.…”

Section: Resultsmentioning

confidence: 99%

Adsorption of Alkyldimethylamine and Alkyldimethylphosphine Oxides at Curved Aqueous Solution/Silica Interfaces, Studied Using Microcalorimetry

Pettersson

Rosenholm

2002

Langmuir

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We report on microcalorimetric studies of the adsorption of octyldimethylamine oxide (C8DAO), decyldimethylamine oxide (C10DAO), dodecyldimethylamine oxide (C12DAO), and decyldimethylphosphine oxide (C10DPO) on mesoporous, low surface charge density silica gel from aqueous solutions at 298.15 K. Displacement enthalpies combined with adsorption isotherms were measured at natural pH, at which the dilute solutions of the alkyldimethylamine oxides were mixed cationic-nonionic. All surfactants studied adsorb exothermally from dilute solution by forming hydrogen bonding between nonionic headgroup and surface silanol groups, and by electrostatic interactions between ionic adsorbates and oppositely charged surface sites. All the cationic surfactant species and dissociated silanol groups do not lose all their counterions and hydrated water when interacting electrostatically with each other. The surfaces with the exothermally adsorbed constrained species induce endothermic, hydrophobic interactions that increase the adsorption and result in surface self-assembled structures at surfactant contents in solution well below the bulk critical micelle concentration (cmc). The endothermic differential molar enthalpies of displacement of the decyl group substituted surfactants studied show a maximum when the adsorption saturates near the cmc. They form globular surface micelles at the solution/SiO2 interface. Due to interaggregate interactions, the interfaces between neighboring globular surface assemblies are not fully hydrated. C12DAO suddenly forms hemimicelles in the low-affinity adsorption region involving rearrangement of adsorbate species, and probably ellipsoidal micellar aggregates in the high-affinity region at the hydrophilic silica interface. The aggregation number is four C12DAO species per hemimicelle on the average. The adsorption mechanism of C12DAO seems to be different from those of C10DAO and C10DPO.

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Thermodynamics of Micellar Systems: Volumes and Heat Capacities of Alkyldimethylamine Oxides in Water

Cited by 11 publications

References 19 publications

Calorimetric Study of the Adsorption of Short-Chain Nonionic Surfactants on Silica Glass and Graphite: Dimethyldecylamine Oxide and Octyl Monoglucoside

Calorimetric Study of the Adsorption of Short-Chain Nonionic Surfactants on Silica Glass and Graphite: Dimethyldecylamine Oxide and Octyl Monoglucoside

Apparent Molar Volumes and Heat Capacities of Various Adsorbed Additives on Polystyrene Latexes

Adsorption of Alkyldimethylamine and Alkyldimethylphosphine Oxides at Curved Aqueous Solution/Silica Interfaces, Studied Using Microcalorimetry

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