Potential-step chronocoulometric study of a surfactant with a redox center

Harima, Yutaka; Yamashita, Kazuo

doi:10.1016/0013-4686(90)90085-e

Cited by 7 publications

(2 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We did not obtain direct evidence of the presence of micelles: studies based on light scattering are in progress and will be reported elsewhere. Past investigations based on dye solubilization 7 and potential-step chronocoulometry, however, have reported the cmc of II + to be 0.07 mM in 0.2 M Li 2 SO 4 . These past measurements of the cmc agree closely with the concentration (0.1 mM in 0.1 M Li 2 SO 4 ) at which we observe a “break” in the surface tension plot of II + and support our interpretation of the “break” as the cmc.…”

Section: Resultsmentioning

confidence: 92%

Ferrocenyl Surfactants at the Surface of Water: Principles for Active Control of Interfacial Properties

1996

View full text Add to dashboard Cite

We report the use of redox-active surfactants Fc(CH2)nN + (CH3)3‚Br -, where Fc ) ferrocene ) [η 5 -C5H5]-Fe[η 5 -C5H5] and n ) 8, 11, or 15, in a study of principles for active control of interfacial properties of aqueous solutions. By comparing the surface activity of Fc(CH2)11N + (CH3)3 with that of HO(CH2)11N + -(CH3)3 and CH3(CH2)11N + (CH3)3, we demonstrate that Fc(CH2)nN + (CH3)3 behave as unsymmetrical bolaform surfactants with one ionic "head" group (N + (CH3)3) and one nonionic "head" group (Fc), whereas ferrocenyl surfactants, when oxidized to Fc + (CH2)nN + (CH3)3, have properties of symmetrical bolaform surfactants such as N + (CH3)3(CH2)15N + (CH3)3. Oxidation of Fc(CH2)nN + (CH3)3 to Fc + (CH2)nN + (CH3)3 leads to changes in interfacial properties through three mechanisms, at least. First, near their critical micellar concentrations (cmc's), oxidation caused desorption of monolayers of Fc(CH2)8N + (CH3)3 and Fc(CH2)11N + (CH3)3 from the surfaces of their aqueous solutions, thereby recovering the surface tension of the aqueous electrolyte. We measured changes in surface tension as large as 23 mN/m. Second, at concentrations greater than the cmc, oxidation of Fc(CH2)11N + (CH3)3 caused little, if any, change in the excess surface concentration of surfactant. The accompanying increase in the density of charge within the monolayer did, however, cause a decrease in surface tension of 6 mN/m. Third, oxidation of Fc(CH2)15N + (CH3)3 caused its monolayers at the surface of water to change from condensed states to expanded ones at constant surface pressure. We infer the phase transition within the monolayer to be driven by changes in conformation that accompany the transfer of ferrocene, upon oxidation, from the outer region (side in contact with air) of the condensed monolayer into contact with the aqueous subphase.

show abstract

Section: Resultsmentioning

confidence: 92%

Ferrocenyl Surfactants at the Surface of Water: Principles for Active Control of Interfacial Properties

1996

View full text Add to dashboard Cite

show abstract

“…In this paper, we report the results of a study in which we sought to demonstrate that it is possible to control polymer−surfactant interactions by using redox-active surfactants in combination with electrochemical methods. The study is based on the redox-active surfactant (11-ferrocenylundecyl)trimethylammonium bromide (FTMA, seen in Figure a). − This surfactant forms micelles at concentrations above 0.1 mM in aqueous solutions containing 0.1 M Li 2 SO 4 at pH 2 and 25 °C. , These micelles can be disassembled by oxidation of the ferrocene group within the surfactant to a ferrocenium ion. Past studies have established that the oxidation and disassembly of micelles is reversible. , We hypothesized that changes in the self-assembly of FTMA with oxidation state would change the interactions of FTMA with polymers such as ethyl(hydroxyethyl) cellulose (EHEC) in solution.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Control of the Interactions of Polymers and Redox-Active Surfactants

Hays

Abbott

2005

Langmuir

View full text Add to dashboard Cite

We report the characterization of aqueous solutions (0.1 M Li(2)SO(4)) of dilute ethyl(hydroxyethyl) cellulose (EHEC) mixed with the redox-active surfactant (11-ferrocenylundecyl)trimethylammonium bromide (FTMA) by measurements of clouding temperatures and dynamic light scattering. The investigation sought to test the hypothesis that FTMA, which forms micelles in aqueous solution in its reduced state but not in its oxidized state, would permit reversible control over the formation of polymer-surfactant complexes in solution. Our measurements revealed that low concentrations of reduced FTMA enhance aggregation, whereas high concentrations of reduced FTMA disperse polymer-surfactant aggregates. This behavior is qualitatively similar to both dodecyltrimethylammonium bromide and sodium dodecyl sulfate and reflects cooperative interactions between FTMA and EHEC. In contrast, oxidized FTMA was found not to promote EHEC aggregation at low concentrations of oxidized FTMA nor disperse EHEC aggregates at high concentrations. Measurements of dynamic light scattering revealed that the reduction of oxidized FTMA in solutions of EHEC containing 0.1-0.3 mmolal FTMA causes an increase in the sizes of polymer-surfactant aggregates of more than 1 order of magnitude. Our cloud point measurements also revealed that clouding can be induced isothermally via the electrochemical reduction of oxidized FTMA at room temperature at FTMA concentrations between 0.4 and 10 mmolal. In contrast, at concentrations of FTMA greater than 15 mmolal, the reduction of oxidized FTMA induces the clearing of EHEC solutions. We conclude that aggregation of EHEC in dilute solutions can be controlled by the manipulation of the oxidation state of FTMA.

show abstract

Electrochemical investigation of cetylpyridinium cation micelle adsorption at the Hg | aqueous solution interface

Nikitas

Pappa-Louisi

Antoniou

1994

Journal of Electroanalytical Chemistry

View full text Add to dashboard Cite

Potential-step chronocoulometric study of a surfactant with a redox center

Cited by 7 publications

References 10 publications

Ferrocenyl Surfactants at the Surface of Water: Principles for Active Control of Interfacial Properties

Ferrocenyl Surfactants at the Surface of Water: Principles for Active Control of Interfacial Properties

Electrochemical Control of the Interactions of Polymers and Redox-Active Surfactants

Electrochemical investigation of cetylpyridinium cation micelle adsorption at the Hg | aqueous solution interface

Contact Info

Product

Resources

About