Determining the forces between polystyrene latex spheres using differential electrophoresis

Darrell Velegol, John L. Anderson, Stephen Garoff

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

The attractive force holding two polystyrene latex spheres in a doublet was measured by the method of differential electrophoresis. The two spheres of each doublet had different surface chemistries (e.g., sulfate and carboxylate) and different ζ potentials ζ1 and ζ2. The doublet acted as a dipole, and an applied electric field (E) caused the doublet to rotate such that the less negative sphere pointed in the direction of the field. Once the doublet was aligned, the tendency of the spheres to translate at different velocities produced a tension, the "electrophoretic displacement force". This force, proportional to ζ2 - ζ1 and the applied electric field E, is calculated from solutions to the electrostatic and hydrodynamic equations. For our systems (5 μm diameter spheres, ζ2 - ζ1 ≈ 40 mV, E ≈ 200 V/cm) the electrophoretic displacement force was 20-50 pN, which is more than a factor of 10 greater than the maximum attractive force predicted by DLVO theory for doublets in a secondary minimum. In no case could we break the doublets with the electrophoretic displacement force. We conclude that DLVO theory is inadequate for our colloidal system, either because the doublets were in a primary minimum (even though DLVO theory predicted an insurmountable energy barrier) or because the depth of the secondary minimum was more than a factor of 10 greater than predicted.

Original languageEnglish (US)
Pages (from-to)4103-4110
Number of pages8
JournalLangmuir
Volume12
Issue number17
StatePublished - Aug 21 1996

Fingerprint

electrophoresis
latex
Electrophoresis
Latexes
Polystyrenes
polystyrene
Electric fields
Energy barriers
Surface chemistry
electric fields
hydrodynamic equations
Sulfates
Electrostatics
Hydrodynamics
carboxylates
styrofoam
sulfates
tendencies
chemistry
electrostatics

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

Cite this

Velegol, Darrell ; Anderson, John L. ; Garoff, Stephen. / Determining the forces between polystyrene latex spheres using differential electrophoresis. In: Langmuir. 1996 ; Vol. 12, No. 17. pp. 4103-4110.
@article{2f666294f98d4721b2b868bb6946d05a,
title = "Determining the forces between polystyrene latex spheres using differential electrophoresis",
abstract = "The attractive force holding two polystyrene latex spheres in a doublet was measured by the method of differential electrophoresis. The two spheres of each doublet had different surface chemistries (e.g., sulfate and carboxylate) and different ζ potentials ζ1 and ζ2. The doublet acted as a dipole, and an applied electric field (E∞) caused the doublet to rotate such that the less negative sphere pointed in the direction of the field. Once the doublet was aligned, the tendency of the spheres to translate at different velocities produced a tension, the {"}electrophoretic displacement force{"}. This force, proportional to ζ2 - ζ1 and the applied electric field E∞, is calculated from solutions to the electrostatic and hydrodynamic equations. For our systems (5 μm diameter spheres, ζ2 - ζ1 ≈ 40 mV, E∞ ≈ 200 V/cm) the electrophoretic displacement force was 20-50 pN, which is more than a factor of 10 greater than the maximum attractive force predicted by DLVO theory for doublets in a secondary minimum. In no case could we break the doublets with the electrophoretic displacement force. We conclude that DLVO theory is inadequate for our colloidal system, either because the doublets were in a primary minimum (even though DLVO theory predicted an insurmountable energy barrier) or because the depth of the secondary minimum was more than a factor of 10 greater than predicted.",
author = "Darrell Velegol and Anderson, {John L.} and Stephen Garoff",
year = "1996",
month = "8",
day = "21",
language = "English (US)",
volume = "12",
pages = "4103--4110",
journal = "Langmuir",
issn = "0743-7463",
publisher = "American Chemical Society",
number = "17",

}

Determining the forces between polystyrene latex spheres using differential electrophoresis. / Velegol, Darrell; Anderson, John L.; Garoff, Stephen.

In: Langmuir, Vol. 12, No. 17, 21.08.1996, p. 4103-4110.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Determining the forces between polystyrene latex spheres using differential electrophoresis

AU - Velegol, Darrell

AU - Anderson, John L.

AU - Garoff, Stephen

PY - 1996/8/21

Y1 - 1996/8/21

N2 - The attractive force holding two polystyrene latex spheres in a doublet was measured by the method of differential electrophoresis. The two spheres of each doublet had different surface chemistries (e.g., sulfate and carboxylate) and different ζ potentials ζ1 and ζ2. The doublet acted as a dipole, and an applied electric field (E∞) caused the doublet to rotate such that the less negative sphere pointed in the direction of the field. Once the doublet was aligned, the tendency of the spheres to translate at different velocities produced a tension, the "electrophoretic displacement force". This force, proportional to ζ2 - ζ1 and the applied electric field E∞, is calculated from solutions to the electrostatic and hydrodynamic equations. For our systems (5 μm diameter spheres, ζ2 - ζ1 ≈ 40 mV, E∞ ≈ 200 V/cm) the electrophoretic displacement force was 20-50 pN, which is more than a factor of 10 greater than the maximum attractive force predicted by DLVO theory for doublets in a secondary minimum. In no case could we break the doublets with the electrophoretic displacement force. We conclude that DLVO theory is inadequate for our colloidal system, either because the doublets were in a primary minimum (even though DLVO theory predicted an insurmountable energy barrier) or because the depth of the secondary minimum was more than a factor of 10 greater than predicted.

AB - The attractive force holding two polystyrene latex spheres in a doublet was measured by the method of differential electrophoresis. The two spheres of each doublet had different surface chemistries (e.g., sulfate and carboxylate) and different ζ potentials ζ1 and ζ2. The doublet acted as a dipole, and an applied electric field (E∞) caused the doublet to rotate such that the less negative sphere pointed in the direction of the field. Once the doublet was aligned, the tendency of the spheres to translate at different velocities produced a tension, the "electrophoretic displacement force". This force, proportional to ζ2 - ζ1 and the applied electric field E∞, is calculated from solutions to the electrostatic and hydrodynamic equations. For our systems (5 μm diameter spheres, ζ2 - ζ1 ≈ 40 mV, E∞ ≈ 200 V/cm) the electrophoretic displacement force was 20-50 pN, which is more than a factor of 10 greater than the maximum attractive force predicted by DLVO theory for doublets in a secondary minimum. In no case could we break the doublets with the electrophoretic displacement force. We conclude that DLVO theory is inadequate for our colloidal system, either because the doublets were in a primary minimum (even though DLVO theory predicted an insurmountable energy barrier) or because the depth of the secondary minimum was more than a factor of 10 greater than predicted.

UR - http://www.scopus.com/inward/record.url?scp=5244346843&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=5244346843&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:5244346843

VL - 12

SP - 4103

EP - 4110

JO - Langmuir

JF - Langmuir

SN - 0743-7463

IS - 17

ER -