Characterization of colloidal polymer particles through stability ratio measurements

A Vaccaro, J Sefcik, M Morbidelli

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

We propose a general methodology for the estimation of the doublet formation rate constant (proportional to the stability ratio of primary particles) in colloidal dispersions from measurements obtained by common optical techniques, such as dynamic light scattering, static light scattering (nephelometry) or turbidimetry. In contrast to previous approaches relying on the initial slopes of the measured quantities, such as the mean hydrodynamic radius, scattered light intensity or turbidity, we introduce a transformation of the measurables to properly scaled quantities, which grow linearly in time with a slope proportional to the doublet formation rate. Analysis of systematic and random errors allows one to control the error in the estimated value of the aggregation rate. Using this approach, we measured the aggregation rate constant of colloidal polymer particles prepared by surfactant-free emulsion copolymerization of styrene and 2-hydroxyethyl methacrylate (HEMA). It was found that the stability ratio at constant ionic strength decreases with increasing dilution of the original polymer latex. This can be explained by the presence of non-reacted stabilizing species (most likely oxidized HEMA) that desorb from the particle surface upon latex dilution and thus diminish the repulsive interactions between particles. In order to check if the stability of latex particles is influenced by reversibly adsorbed species it is always necessary to perform aggregation experiments at various dilutions.

LanguageEnglish
Pages1157-1167
Number of pages11
JournalPolymer
Volume46
Issue number4
DOIs
Publication statusPublished - 7 Feb 2005

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Latex
Latexes
Dilution
Polymers
Agglomeration
Particles (particulate matter)
Rate constants
Styrene
Random errors
Particle interactions
Systematic errors
Dynamic light scattering
Turbidity
Ionic strength
Emulsions
Dispersions
Surface-Active Agents
Light scattering
Copolymerization
Surface active agents

Keywords

  • colloids
  • aggregation
  • kinetics

Cite this

Vaccaro, A ; Sefcik, J ; Morbidelli, M . / Characterization of colloidal polymer particles through stability ratio measurements. In: Polymer. 2005 ; Vol. 46, No. 4. pp. 1157-1167.
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Characterization of colloidal polymer particles through stability ratio measurements. / Vaccaro, A ; Sefcik, J ; Morbidelli, M .

In: Polymer, Vol. 46, No. 4, 07.02.2005, p. 1157-1167.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Characterization of colloidal polymer particles through stability ratio measurements

AU - Vaccaro, A

AU - Sefcik, J

AU - Morbidelli, M

PY - 2005/2/7

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N2 - We propose a general methodology for the estimation of the doublet formation rate constant (proportional to the stability ratio of primary particles) in colloidal dispersions from measurements obtained by common optical techniques, such as dynamic light scattering, static light scattering (nephelometry) or turbidimetry. In contrast to previous approaches relying on the initial slopes of the measured quantities, such as the mean hydrodynamic radius, scattered light intensity or turbidity, we introduce a transformation of the measurables to properly scaled quantities, which grow linearly in time with a slope proportional to the doublet formation rate. Analysis of systematic and random errors allows one to control the error in the estimated value of the aggregation rate. Using this approach, we measured the aggregation rate constant of colloidal polymer particles prepared by surfactant-free emulsion copolymerization of styrene and 2-hydroxyethyl methacrylate (HEMA). It was found that the stability ratio at constant ionic strength decreases with increasing dilution of the original polymer latex. This can be explained by the presence of non-reacted stabilizing species (most likely oxidized HEMA) that desorb from the particle surface upon latex dilution and thus diminish the repulsive interactions between particles. In order to check if the stability of latex particles is influenced by reversibly adsorbed species it is always necessary to perform aggregation experiments at various dilutions.

AB - We propose a general methodology for the estimation of the doublet formation rate constant (proportional to the stability ratio of primary particles) in colloidal dispersions from measurements obtained by common optical techniques, such as dynamic light scattering, static light scattering (nephelometry) or turbidimetry. In contrast to previous approaches relying on the initial slopes of the measured quantities, such as the mean hydrodynamic radius, scattered light intensity or turbidity, we introduce a transformation of the measurables to properly scaled quantities, which grow linearly in time with a slope proportional to the doublet formation rate. Analysis of systematic and random errors allows one to control the error in the estimated value of the aggregation rate. Using this approach, we measured the aggregation rate constant of colloidal polymer particles prepared by surfactant-free emulsion copolymerization of styrene and 2-hydroxyethyl methacrylate (HEMA). It was found that the stability ratio at constant ionic strength decreases with increasing dilution of the original polymer latex. This can be explained by the presence of non-reacted stabilizing species (most likely oxidized HEMA) that desorb from the particle surface upon latex dilution and thus diminish the repulsive interactions between particles. In order to check if the stability of latex particles is influenced by reversibly adsorbed species it is always necessary to perform aggregation experiments at various dilutions.

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