A differential scanning calorimetry study of a binary system

Chernik, G. G.; Sokolova, E. P.

doi:10.1016/0021-9797(91)90337-8

Cited by 13 publications

(3 citation statements)

References 16 publications

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“…Therefore, the phase boundaries drawn in Figure for these two-phase regions should be regarded as assumed ones. Chernik and co-workers , have demonstrated that these phase boundaries can be successfully detected for a dimethyldecylphosphine oxide/water system by DSC measurements employing a scanning rate slower than 0.5 °C/min.…”

Section: Resultsmentioning

confidence: 98%

Phase Behavior of Heptaethylene Glycol Dodecyl Ether and Its Aqueous Mixture Revealed by DSC and FT-IR Spectroscopy

et al. 2001

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The phase behavior of heptaethylene glycol dodecyl ether (C12E7) and its aqueous mixture was investigated by means of differential scanning calorimetry (DSC) and Fourier transform infrared (FT-IR) spectroscopy in the temperature range from -20 to 70 °C. Phase boundaries among various phases including mesomorphic phases were determined on the basis of DSC thermograms, from which the binary phase diagram of this mixture system was constructed. According to the phase diagram, the mixture with the composition of 31 wt % H2O exhibits the following phase sequence with increasing temperature: solid f H1 (normal hexagonal) f V1 (normal bicontinuous-type cubic) f LR (lamellar) f liquid. FT-IR measurements for the mixture with this composition revealed the following features concerning the conformational structure of the C12E7 molecule and the interaction between the surfactant and D2O in each phase. In the solid phase, the polyoxyethylene (POE) chain of the surfactant molecule has a rather extended structure with a trans-rich conformation, in contrast to the case of pure C12E7, in which a helical structure is dominant. When the solid phase transforms to the H1 phase, the hydrogen-bond interaction between C12E7 molecules and between C12E7 and water are both weakened, and the fraction of gauche-conformer in the POE chain increases, whereas the alkyl chain adjacent to the POE chain remains, taking a rather trans-zigzag conformation. The enhanced fraction of gauche-conformer in the POE chain suggests that the POE chain has a helical structure in this phase. The increase in temperature within the H1 region causes a conformational change in both the POE chain and the alkyl chain of the surfactant to a more disordered structure. Among the phases of V1, LR, and liquid, no significant difference is seen in the conformational structure and interaction with water molecules of the surfactant.

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Section: Resultsmentioning

confidence: 98%

Phase Behavior of Heptaethylene Glycol Dodecyl Ether and Its Aqueous Mixture Revealed by DSC and FT-IR Spectroscopy

et al. 2001

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“…The phase diagrams and thermodynamics of aqueous two-component systems of alkyldimethylamine oxides or alkyldimethylphosphine oxides have been extensively studied. − However, a more systematic study on the self-assembly mechanism of adsorption at aqueous interfaces of amorphous SiO 2 with parameters such as variations in hydrophilic structural elements (amine or phoshine oxide), nonionic and cationic characters, and the length of the hydrocarbon chain is still missing from the literature. The long-chain alkyldimethylamine oxides studied have been used in various technological fields such as detergent formulations, cosmetics, viscosity builder, wetting agent, emulsifier, foam stabilizer, and antistatic agent.…”

Section: Introductionmentioning

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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“…Transition temperatures and enthalpies are often determined and used to draw the limits of existence of the different phases of surfactant-based systems [1][2][3][4][5][6]. Transition temperatures and enthalpies are often determined and used to draw the limits of existence of the different phases of surfactant-based systems [1][2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

DSC Analysis of Surfactant-Based Microstructures

Garti¹

2000

Surfactant Science

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A differential scanning calorimetry study of a binary system

Cited by 13 publications

References 16 publications

Phase Behavior of Heptaethylene Glycol Dodecyl Ether and Its Aqueous Mixture Revealed by DSC and FT-IR Spectroscopy

Phase Behavior of Heptaethylene Glycol Dodecyl Ether and Its Aqueous Mixture Revealed by DSC and FT-IR Spectroscopy

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

DSC Analysis of Surfactant-Based Microstructures

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