Thermodynamic factors of the sol—gel transition II. The role of short- and long-range forces in thermodynamics of colloid stability

Shchukin, E. D.; Yaminsky, V.V.

doi:10.1016/0166-6622(88)80003-9

Cited by 8 publications

(6 citation statements)

References 13 publications

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“…This is a puzzle, particularly surprising because an enhancement of adhesion by for example cationic surfactants can be detected by either of the two techniques. Both give the same results, , in accordance with AFM, SFA, and so forth. Similar measurements were carried out with hydrophobic balls in a variety of liquids and solutions.…”

Section: Discussionsupporting

confidence: 82%

“…Similar measurements were carried out with hydrophobic balls in a variety of liquids and solutions. Here again results obtained with different techniques agree with each other. ,, Static and viscous drag forces can both be measured, and alternative techniques do not contradict each other.…”

Section: Discussionsupporting

confidence: 79%

“…The critical value of the free energy of adhesion at the onset of coagulation is several mJ/m 2 in this case. A detailed thermodynamic account of the effect can be given . The coagulation/gelation takes place immediately after ethanol is partly substituted for water.…”

Section: Introductionmentioning

confidence: 99%

“…Interestingly, this is in turn the energy at the coagulation threshold, as is observed experimentally and is explained theoretically for dispersions of methylated silica in mixed solvents. In the latter case, however, the explanation is done by invoking short- and long-range forces between colloid particles, as measured between macroscopic surfaces, with thermodynamic considerations of the sol−gel equilibrium. , The interaction here is reversible and a new level of adhesion is reached immediately each time when the concentration of water in ethanol is changed. This corresponds to immediate enhancement of coagulation when the critical level of adhesion is reached by adding water.…”

Section: Introductionmentioning

confidence: 99%

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Interaction between Surfaces of Fused Silica in Water. Evidence of Cold Fusion and Effects of Cold Plasma Treatment

1998

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Silica colloids and silica glass surfaces have often been used as “model” systems to study coagulation, rheology, contact angles, and surface forces. But the silica−water interface is highly changeable and reactive. It has stubbornly refused to conform to theoretical models of an ideal hydrophilic substrate. In this study we show why this is and demonstrate some of the diverse properties of this surface. Surfaces of fused quartz swell under water to form layers of silica gel. We report here on how this well-known effect shows up in surface force measurements. Peculiar effects occur already at normal pH. Over a period of time after the surfaces are immersed in water, identical interaction patterns occur on approach and on separation. The double-layer repulsion extends from large distances down to the contact. Interaction hysteresis develops later. Adhesion and other specific interactions, particularly at short range, develop with time. The evolution that extends for hours and days is variable in its manifestations from experiment to experiment. Precise conditions of solidification from the melt, and aspects of the thermal history of the glass transition during preparation of vitreous silica samples, can be factors in this variability. Surface degradation by formation of silica gel layers on contact with water can be enhanced by cold plasma treatment and by UV radiation. Pull-off forces increase with an increase of contact time. They also show a memory of conditions of previous contacts. Electrolytes enhance the adhesion. Complicated polycondensation equilibria, influenced by nonspecific and specific ion effects, pH, nonionic solutes, and temperature distinguish the chemistry of silicic acid. All are involved in the interaction. These curious, history-dependent, surface forces were first reported half a century ago. They were attributed by Malkina and Derjaguin to “water structure”. The effects that led later to contentious and disputed notions of hydration forces can be manifest as an “extra” repulsion or an “extra” attraction. They are here related to surface gelation. These surface force observations have distinct parallels in thixotropy and other peculiarities of “anomalous” coagulation and rheological behavior of concentrated and diluted dispersions of colloid silica in water. The effect of “cold fusion” between macroscopic surfaces of pure silica in pure water is here studied at room temperature with a new interfacial gauge force measuring technique. This spontaneous welding due to the presence of water can be hindered by stray contact shear, which interferes with observation by colloid probe and surface force techniques. The peculiar properties of the silica−water interface are discussed in connection with earlier experimental work that led to theoretical notions of polywater and non-DLVO forces.

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Section: Discussionsupporting

confidence: 82%

Section: Discussionsupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Interaction between Surfaces of Fused Silica in Water. Evidence of Cold Fusion and Effects of Cold Plasma Treatment

1998

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“…In 5 × 10 -5 M CTAB the interaction for unpretreated silica glass is purely attractive. − On the other hand for the silanated surfaces at this concentration there is a repulsion with a characteristic decay length of about 30 nm. At a distance of about 10 nm, from which the surfaces jump into contact, a pronounced barrier is formed.…”

Section: Resultsmentioning

confidence: 98%

Surface Activity and Ion Exchange. A Study via Surface Tension, Wetting Tension, and Surface Force Techniques

1996

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The surface pressure of adsorbed layers of the cationic surfactants lauryl-and cetyltrimethylammonium bromide and ion exchange effects caused by the electrolytes sodium bromide and sodium acetate were studied at interfaces of water with air and methylated glass. New techniques used made possible a quantitative comparison of dynamic and equilibrium surface tension, wetting tension, and surface force (adhesion) isotherms and a control of surface purity. The surface activity is slightly higher at the interface with air than at the interface with the hydrophobic solid. In other respects, surface pressure isotherms for the two interfaces are similar. The methylated surfaces in pure water are effectively uncharged. Their mutual repulsion in solutions is due to ionic surfactant adsorption and is described at long distances by DLVO theory. At contact the interaction is always attractive but the adhesion is reduced according to the repulsive surface pressure contribution. The distance from which the surfaces jump into contact decreases with increasing surfactant adsorption at low surfactant and electrolyte concentrations. The decrease is correlated with the decrease of the contact angle rather than to van der Waals and double layer forces. As the surface pressure increases the wetting tension changes sign from negative to positive and the contact angle falls below 90°. The jump-in distance becomes twice the thickness of the condensed monolayer. The barrier height changes according to the variation of the surface pressure. Sodium bromide increases while sodium acetate decreases the surface pressure of micellar solutions. In agreement with the ion exchange trend the contact adhesion decreases and increases accordingly. Exchange of bromide counterion for acetate leads to exceptionally large values of the negative surface activity.

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Thermodynamic Criterion of Spontaneous Dispersion

Shchukin

Pertsov

2006

Colloid Stability

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Thermodynamic factors of the sol—gel transition II. The role of short- and long-range forces in thermodynamics of colloid stability

Cited by 8 publications

References 13 publications

Interaction between Surfaces of Fused Silica in Water. Evidence of Cold Fusion and Effects of Cold Plasma Treatment

Interaction between Surfaces of Fused Silica in Water. Evidence of Cold Fusion and Effects of Cold Plasma Treatment

Surface Activity and Ion Exchange. A Study via Surface Tension, Wetting Tension, and Surface Force Techniques

Thermodynamic Criterion of Spontaneous Dispersion

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