Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
Counterion effects on adsorbed micellar shape: Experimental study of the role of polarizability and charge
Autore:
Subramanian, V; Ducker, WA;
Indirizzi:
Virginia Tech, Dept Chem, Blacksburg, VA 24061 USA Virginia Tech Blacksburg VA USA 24061 Dept Chem, Blacksburg, VA 24061 USA
Titolo Testata:
LANGMUIR
fascicolo: 10, volume: 16, anno: 2000,
pagine: 4447 - 4454
SICI:
0743-7463(20000516)16:10<4447:CEOAMS>2.0.ZU;2-L
Fonte:
ISI
Lingua:
ENG
Soggetto:
SOLID-LIQUID INTERFACES; DIRECT VISUALIZATION; AGGREGATE GEOMETRY; SURFACE FORCES; ADSORPTION; BINDING; SPECIFICITY; SCATTERING; MICROSCOPY; BEHAVIOR;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
29
Recensione:
Indirizzi per estratti:
Indirizzo: Ducker, WA Virginia Tech, Dept Chem, Blacksburg, VA 24061 USA Virginia Tech Blacksburg VA USA 24061 Blacksburg, VA 24061 USA
Citazione:
V. Subramanian e W.A. Ducker, "Counterion effects on adsorbed micellar shape: Experimental study of the role of polarizability and charge", LANGMUIR, 16(10), 2000, pp. 4447-4454

Abstract

We have used atomic force microscopy (AFM) to measure the shape of micelles adsorbed to the interface between hydrophilic silica and solutions of hexadecyltrimethylammonium (CTA(+)) ions in the presence of various counterions. Spherical CTA(+) surface micelles are adsorbed from solutions containingsalts of CH3CO2-, CO32-, SO42-, SO32-, and HSO32-, even at high salt concentrations (>100 mM). Cl- and Br- form slightly oblate micelles near their respective critical micelle concentrations. Addition of Br- causes a transformation to cylindrical micelles whereas addition of Cl- does not. The difference between Br- and Cl- is similar to the behavior observed previously inbulk solution. Addition of S2O32- or CS32- or HS-/S2- transforms sphericalmicelles to cylinders. We rationalize these effects on the basis of the hard/soft (unpolarizable/polarizabile) nature of the ions. The ability to effect the sphere-to-cylinder transformation correlates with the availability of a soft anionic atom in the counterion. Presumably, this soft anionic atom promotes partitioning of the ion from the water to the micelle surface, thereby lowering the electrostatic repulsion between headgroups and effecting the sphere-to-cylinder transformation. Surface micelles are observed at concentrations below the critical micelle concentration. For CTABr, AFM can detect surface micelles at concentrations greater than half the critical micelle concentration.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 30/03/20 alle ore 00:53:09