Wall effects in du Noüy ring tensiometry. Theory and experiment

Furlong, D. Neil; Freeman, Pamela A.; Metcalfe, Ian M.; White, Lee R.

doi:10.1039/f19837901701

Cited by 12 publications

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“…Therefore, the ratio of the ring radius to the dish radius could be calculated and was found to be 4.8/0.954 = 5.03. The size of the crystallizing dishes was initially chosen based on this ratio to avoid wall effects (14). • To prevent any effects due to the floor of the container, at least 100-mL samples were used in the crystallizing dishes.…”

Section: Methodsmentioning

confidence: 99%

Synthesis and characterization of maltose fatty acid monoesters as biosurfactants

Allen

Tao

2002

J Surfact & Detergents

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Maltose long-chain fatty acid esters (MFAE), esterified at the 6 and 6′ position, were synthesized with stearic, palmitic, myristic, and oleic groups. Synthesis yields were 15-20% based on initial maltose present, and structural confirmation was obtained using plasma desorption mass spectrometry and nuclear magnetic resonance spectroscopy. These surfactants have surface tensions in the range of 34-36 dyn/cm at their critical micelle concentrations (CMC) of approximately 10 −5 -10 −6 mol/L. The increased chain lengths have a marked effect, reducing CMC values for MFAE by approximately three orders of magnitude over similar carbohydrate-based dodecyl chain sources. Within chain lengths between 14 and 18 carbons, the rate of change in CMC is significant and decreases with increasing chain length for MFAE. The melting points of MFAE are approximately 40°C, and the heat capacities range from 1.6 to 1.9 J/g·K. These numbers are comparable to those of sucrose esters, indicating their applicability in similar uses. However, because MFAE, unlike sucrose, possess an anomeric carbohydrate carbon position, these surfactants maintain their reducing nature and are susceptible to further derivatization. They are also synthesized from renewable, economical carbohydrates and lipids and may provide an excellent alternative to petrochemical-derived products.Paper no. S1273 in JSD 5, 245-255 (July 2002).KEY WORDS: Biosurfactants, carbohydrate esters, nonionic surfactants, sugar esters.Carbohydrate polysaccharides, produced naturally in plants, account for approximately 75% of the dry weight of the biological world and nearly 80% of the human caloric diet (1). Currently, corn, potatoes, tapioca, and wheat plants are all processed to provide common sources of starch. Carbohydrates are of interest because of the number of reactive hydroxyl groups they contain. Condensation of one of the reactive groups of a saccharide with a fatty acid produces a surface-active agent. Carbohydrate-based surfactants have been used primarily in the cosmetic, detergent, food, and pharmaceutical industries (2) because they are physiologically, dermatologically, and biologically acceptable (3). Because they are odorless, tasteless, nonionic, and biodegradable, they compare well in overall performance (i.e., emulsification, detergency, foam power, wettability, and other related properties) with other surface-active compounds (4). To date, several major types of carbohydratebased surfactants are commonly used worldwide, including sorbitan esters, sucrose esters, alkyl glycosides, and glucoseamide derivatives (5-8).There are three significant limitations with a majority of the existing petroleum-based surfactants. First, they are monofunctional, (i.e., can contribute only one desired property to a formulation). Therefore, several surfactants must be combined to achieve all desired properties.Second, many surfactants are incompatible and cannot function effectively with other surfactants. Cationic and anionic surfactants neutralize each other if they are combin...

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Section: Methodsmentioning

confidence: 99%

Synthesis and characterization of maltose fatty acid monoesters as biosurfactants

Allen

Tao

2002

J Surfact & Detergents

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“…In previous AFM surface tension measurements in air the liquid drops were often very large or flat pools of liquid where edge effects were neglected. , A detailed analysis on edge effects for the geometry of a drop below the capillary length has not been performed. However, earlier theoretical and experimental studies of edge effects in the du Noüy ring method and other force balance methods suggest that the ratio of the distance to the drop edge to probe diameter must be large to neglect edge effects. , The analysis performed by Furlong et al showed in a dimensionless analysis that the ratio of the probe object to the distance from the edge must be large (on the order of 5 for the du Noüy ring). This analysis is derived using interfacial continuum mechanics principles, which are expected to apply to the microdrops used in this study as well.…”

Section: Resultsmentioning

confidence: 99%

Novel Characterization of Microdrops and Microbubbles in Emulsions and Foams Using Atomic Force Microscopy

2011

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The nature of the interface of drops or bubbles and the dynamic interactions between them often mediate or control macroscopic behavior in the formulation and processing of emulsions and foams in solvent extraction, froth flotation, food, personal care products, and microfluidics as well as in many biological processes. Characterization of these interfaces is often complicated due to the small size of the drops and bubbles that may range from the micrometer scale to hundreds of micrometers. We report the direct measurement of the surface or interfacial tension of drops or bubbles in aqueous solutions as a function of the concentration and type of surfactant, using atomic force microscopy (AFM) and a recently developed nanoneedle AFM cantilever. We also demonstrate the viability of imaging drops or bubbles of this size in both tapping and contact imaging modes through a systematic study of parameters, including cantilever spring constant, tip geometry, imaging force, and feedback settings as well as the AFM manufacturer. The imaging study demonstrates the viability of using AFM to visualize complex structures at the oil-water or air-water interface as well as how concentric ring artifacts observed in the literature are the result of earlier AFM instrument limitations.

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Links Between Bulk and Surface Activity in Micellar Solutions

Mesa

Ranieri

1993

Ber Bunsenges Phys Chem

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The surface tension of aqueous surfactant systems and its dependence on the concentration of surfactant in micellar form, Xm ≅ X‐CMC, have been investigated. A modification of the adsorption equation, based on the introduction of activity coefficients, allows to get information on micelle aggregation numbers, 〈N〉, from the slope of surface tension versus ln Xm. The resulting equation, tested on data relative to non ionic surfactants, gives aggregation values in fair good agreement with those inferred from other methods. The limits of the model are discussed in some detail.

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Wall effects in du Noüy ring tensiometry. Theory and experiment

Abstract: A rigorous theory of wall effects in du Nouy ring tensiometry is developed which is no more difficult to compute than the infinite-wall theory of Huh and Mason. The predictions of the theory are compared with experimental measurements on wetting and non-wetting walls.

Cited by 12 publications

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Synthesis and characterization of maltose fatty acid monoesters as biosurfactants

Synthesis and characterization of maltose fatty acid monoesters as biosurfactants

Novel Characterization of Microdrops and Microbubbles in Emulsions and Foams Using Atomic Force Microscopy

Links Between Bulk and Surface Activity in Micellar Solutions

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