Scaling of the kinetics of slow aggregation and gel formation for a fluorinated polymer colloid

P Sandkuhler, J Sefcik, M Morbidelli

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

The aggregation and gelation kinetics in moderately concentrated (0.004 less than or equal to phi(0) less than or equal to 0.1) colloidal dispersions of fluorinated polymer particles has been studied. The aggregation was adjusted to proceed slowly enough to allow a convenient characterization of the kinetics through static and dynamic light scattering on quenched and diluted samples. A population balance model based on second-order aggregation rates is developed to compute the time evolution of the cluster mass distribution, from which we calculate the values of the average radii and structure factor measured by light scattering, so as to allow a direct comparison between measured and calculated quantities. The model suggests the introduction of a dimensionless time which allows the scaling of all the aggregation data on unique master curves defined by only two parameters: the exponent of the power-law aggregation kernel, lambda, and the aggregate fractal dimension, d(f). The predicted master curves were observed experimentally, which confirms the validity of the aggregation model and allows the unique determination of the kinetic and structural parameters of the aggregation process. The cluster growth behaviour, although significantly slower than DLCA, shows power-law kinetics rather than the exponential one typical of RLCA and the cluster structure is characterized by an unexpectedly small fractal dimension, d(f) = 1.7. The occurrence of gelation has been characterized using small amplitude oscillatory shearing to monitor the time evolution of the elastic modulus. It is found that also these curves, together with the gel time value, scale with the stability ratio of primary particles for a given solid volume fraction. We further use the model to calculate the cumulative occupied volume fraction of the growing aggregates and quantify in this way the increasing space filling, which is solid volume fraction dependent. The experimentally determined dimensionless gel times, which are also solid volume fraction dependent, scale then directly with the dimensionless time to reach a certain degree of the space filling in the model. This finding suggests that, like the aggregation kinetics, the gelation kinetics is governed by a second-order rate process.

LanguageEnglish
Pages2062-2077
Number of pages16
JournalLangmuir
Volume21
Issue number5
DOIs
Publication statusPublished - 1 Mar 2005

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Fluorocarbon Polymers
Colloids
colloids
Agglomeration
Gels
gels
scaling
Kinetics
kinetics
polymers
gelation
Polymers
Volume fraction
Gelation
fractals
light scattering
Fractal dimension
curves
shearing
mass distribution

Keywords

  • gelation kinetics
  • aggregation
  • gel formation

Cite this

Sandkuhler, P ; Sefcik, J ; Morbidelli, M . / Scaling of the kinetics of slow aggregation and gel formation for a fluorinated polymer colloid. In: Langmuir. 2005 ; Vol. 21, No. 5. pp. 2062-2077.
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Scaling of the kinetics of slow aggregation and gel formation for a fluorinated polymer colloid. / Sandkuhler, P ; Sefcik, J ; Morbidelli, M .

In: Langmuir, Vol. 21, No. 5, 01.03.2005, p. 2062-2077.

Research output: Contribution to journalArticle

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