Composition of stearic and behenic acid monolayers from sodium-containing substrates

Bagg, J.; Haber, Mary D; Gregor, Harry P.

doi:10.1016/0021-9797(66)90075-0

Cited by 51 publications

(17 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These are in reasonable agreement with the bulk values of the corresponding phenols (shifted by 1−2 p K a units). This type of behavior has been reported for both fatty acids and amines at the air/water interface. ,− One key difference is that for fatty acids and amines the shifts are toward neutral pH, making the monolayer less acidic and basic, respectively. In contrast, the apparent p K a values indicate p -dioctadecanoylcalix[4]arene is a stronger acid at the interface than correspondingly substituted phenols in the bulk.…”

Section: Resultssupporting

confidence: 62%

Static and Dynamic Properties of Calixarene Monolayers at the Air/Water Interface. 1. pH Effects with p-Dioctadecanoylcalix[4]arene

et al. 1999

View full text Add to dashboard Cite

Newly synthesized p-dioctadecanoylcalix[4]arene is shown to form stable monolayers at the air/water interface over a wide pH range (1.8−12). Surface pressure−area isotherms obtained with the Wilhelmy plate technique are used to infer that the molecular packing at the onset of film collapse is consistent with a conelike conformer having all of the phenol oxygens of the calixarenes adsorbed to the interface. Increasing pH leads to a stepwise dissociation to phenoxides and attendant expansion of the monolayer attributable to enhanced electrostatic repulsions among the negatively charged phenoxide polar heads. Analysis of the area per molecule as a function of pH reveals two distinct steps and an intermediate plateau. Considering the presence of two types of chemically inequivalent phenol groups and the potential for intramolecular hydrogen bonding, this behavior was interpreted in terms of acid−base equilibria in which the first step corresponds to an apparent surface pK a,1 ≈ 6.4 while the second step is consistent with an apparent surface pK a,2 ≈ 9.2 (assuming pK a,3, pK a,4 ≫ 12). As for the dynamics of the monolayers, the technique of surface light scattering (SLS) was employed to probe the surface viscoelasticity. Although pH had a dramatic effect on the molecular packing of p-dioctadecanoylcalix[4]arene monolayers, SLS results indicate that all films exhibited the limiting behavior of infinite lateral modulus dynamics when the surface pressure exceeds 1 mN·m-1, and such behavior is established to be independent of pH. From these findings, it is deduced that the packing of the aromatic rings and long octadecanoyl side chains, rather than electrostatic interactions of the phenoxide headgroups, is responsible for the lateral rigidity of such monolayers.

show abstract

Section: Resultssupporting

confidence: 62%

Static and Dynamic Properties of Calixarene Monolayers at the Air/Water Interface. 1. pH Effects with p-Dioctadecanoylcalix[4]arene

et al. 1999

View full text Add to dashboard Cite

show abstract

“…For determination of surface pK a of SAMs, to our best knowledge, few methods, such as contact angle titration [13,14], chemical force titration using atomic force microscopy (AFM) [15,16], quartz crystal microbalance (QCM) [17], surface potential [18], spectroscopy [19] and electrochemical method [20] have been adopted previously. Among them electrochemical method is a more simple and convenient approach than others.…”

Section: Introductionmentioning

confidence: 99%

Determination of Surface pKa of SAM Using an Electrochemical Titration Method

et al. 1999

View full text Add to dashboard Cite

A self-assembled monolayer (SAM) of 3-mercaptopropionic acid (HSCH 2 CH 2 COOH) was formed on a gold electrode. The effect of the charge of the end group on the electrochemical response of Fe(CN) 6 37 at the SAM modi®ed electrode was studied by using cyclic voltammetry. At high pH, when the ±COOH groups are dissociated, Fe(CN) 6 37 current is suppressed; as the solution pH is lowered, Fe(CN) 6 37 current increases. The electrochemical titration curve was obtained by correlating the currents to the different electrolyte pH values, from which the surface pK a was obtained to be 5.2 AE 0.1. Furthermore, a calculation equation was presented to simulate the electrochemical titration. As comparison, the surface pK a was also measured by contact angle titration as 5.6 AE 0.1. The surface pK a values determined by the two methods in our work are consistent and accurate.

show abstract

“…Thus the pKa of monolayers of stearic acid or behenic acid was measured to be 3 to 4 pH units higher than the estimated value in the bulk solution although corrections based on the GouyChapman theory reduced this descrepancy [3]. This alteration in interface pH depends upon the specific electrolytes used to produce the pH in the bulk solution [4,5].…”

Section: Methodsmentioning

confidence: 99%

Intestinal mucous membranes: The role of interfacial phenomena

Sears

1970

Agents and Actions

View full text Add to dashboard Cite

This discussion reviews some of the studies that relate interfacial phenomena to transfer of material across interfaces in both physical chemical and biological systems. The studies mentioned include: the effect of pH differences between the interface and the bulk medium; the requirement for a large negative entropy of activation for transfer between phases; the resistance to transfer of water and salts produced by monolayers of phospholipids; facilitation of lipid transfer based upon the formation of hydrophilic oleomicelles; the facilitation of transfer of molecular aggregates when these aggregates are changed from crystalline to amorphous associations; and finally, the role of chemical reactions to facilitate transfer.There are other interfacial phenomena that influence transfer that have not been discussed, but about which there is increasingly more information. These include: the change in water structure at interfaces; the effect of the electrical double layer; and alterations in viscosity and dielectric at interfacial regions.A large body of information concerning the characteristics of interracial regions has been accumulated. Many elegant techniques have been developed to allow precise measurements. Application of this information to biological systems is important, and application of surface techniques to biological problems is becoming more prevalent. It is necessary to examine these phenomena in order to characterize interfacial transfer for there is scarcely any part of a biological system that is continuously homogenous.

show abstract

Composition of stearic and behenic acid monolayers from sodium-containing substrates

Cited by 51 publications

References 12 publications

Static and Dynamic Properties of Calixarene Monolayers at the Air/Water Interface. 1. pH Effects with p-Dioctadecanoylcalix[4]arene

Static and Dynamic Properties of Calixarene Monolayers at the Air/Water Interface. 1. pH Effects with p-Dioctadecanoylcalix[4]arene

Determination of Surface pKa of SAM Using an Electrochemical Titration Method

Intestinal mucous membranes: The role of interfacial phenomena

Contact Info

Product

Resources

About