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Colloidal gels: 
Multiscale approaches to their structure and rheology Time and schedule Instructor Suggested course references COURSE OUTLINE Lecture 1 Lecture 2 Lecture 3 Lecture 4 Lecture 5 Lecture 6 Other topics of interest: List of attached files

Colloidal gels: 
Multiscale approaches to their structure and rheology

September 2022, École des Ponts

Particulate gels occur in numerous chemical technologies and products composed of colloids and soft particles. These arrested, non-equilibrium states are found in consumer care products, agrochemicals, coatings, pigments and inks–potentially any product or material in which particles are suspended in a fluid phase. Gels occur in part because of the ubiquity of attractive interactions between particles, which can be due to van der Waals interactions, or induced by a non-adsorbing polymer, for example. In industrial and product formulations, the gel yield stress is often sufficiently weak so that that materials may be processed or used effectively—they can flow, be diluted, or redispersed—but otherwise remain stable against gravitational consolidation. However, gels are also prone to unusual and highly unpredictable forms of failure, such as catastrophic delayed gravitational sedimentation, a behavior that threatens the shelf life and spoilage of billions of dollars of products each year. Because of this, colloidal gels have been of long-standing interest to the engineering and scientific community.

Why and how do gels form? What are their properties? What is the relationship between glasses, gels, and equilibrium phases? This course will present an overview of gel structure and rheology from the standpoint of a multiscale description of particle interactions, microstructure, microrheology, and macroscopic rheology. Multiscale models have recently expanded beyond early efforts focused on fractal models of dilute, aggregating suspensions. We will discuss recent advances toward understanding these regimes and highlight emerging methods of micromanipulation and microrheology.

Below is a course outline of the topics that will be covered. A total of 15 hours of lectures will be presented over a three-week period at Université Gustave Eiffel / École des Ponts, Laboratoire Navier in the fall of 2022.

Time and schedule

Meets Tuesday / Thursday, 1430-1700 on
September 8, 13, 15, 20, 22, 27

Instructor

Eric M. Furst, furst@udel.edu
William H. Severns Jr. Distinguished Chair of Chemical Engineering
Department of Chemical and Biomolecular Engineering
University of Delaware

Suggested course references

  • J. N. Israelachvili. Intermolecular and Surface Forces, 3rd edition, 2011. Academic Press: New York.
  • E. M. Furst and T. M. Squires, Microrheology, 2017. Oxford University Press: New York.

 

COURSE OUTLINE

Lecture 1

  1. Colloidal suspensions and characteristics of the colloidal domain
  2. Colloidal interactions:
    1. van der Waals interactions
    2. Electrostatic interactions: polar liquids, non-polar liquids
    3. Grafted and adsorbed polymers and surfactants
    4. Model interactions
  • Download lecture slides (PDF)
  • Supplemental slides - NEW! (PDF)

Reading:

  • Notes on Colloids (PDF)
  • Furst and Squires, chapter 1 (PDF)

Lecture 2

  1. Colloid motion
    1. Mobility and resistance
    2. Hydrodynamic interactions
    3. Brownian motion
  2. Equilibrium
    1. Equilibrium phases of repulsive colloids
    2. Equilibrium phases of attractive colloids
    3. Non-equilibrium states – glasses and gels
  • Download lecture slides (PDF)
  • More on van der Waals forces (PDF)
  • Swan Group Stokesian Dynamics, Live! (LINK)

Reading:

  • Furst and Squires, chapter 2 (PDF)
  • Furst and Squires, chapter 3 (PDF)
  • Furst and Squires, Appendix A (PDF)

Lecture 3

  1. Strongly flocculated suspensions
    1. Colloidal interactions of strongly flocculated suspensions
    2. Kinetics of flocculation
    3. Quiescent structure of flocculated suspensions – fractal gels
  2. Gel rheology
    1. Elastic modulus
    2. Yielding
  • Download lecture slides (PDF)
  • Also download part 1 of lecture 4 below

Reading

  • Furst and Squires, chapter 1 (PDF) has a short section on rheometry and material rheology

Lecture 4

  1. Sedimentation, settling, and redispersion
    1. Delayed collapse
    2. Poroelastic compaction
  2. Methods for characterizing micro-scale structure and dynamics
    1. Scattering
    2. Microscopy
    3. Dynamics of fractal gels
  • Download lecture slides part 1 (PDF)
  • Download lecture slides part 2 - (PDF)

Reading:

  • Slides for now

Lecture 5

  1. Micromanipulation and particle interaction measurements
    1. Surface and colloidal force measurements
    2. Laser tweezers
    3. Mechanics of colloidal bond rupture
  2. Combining direct imaging and micromechanics
    1. Depletion gels
    2. Failure of fractal models and motivation for new multiscale models
    3. Cluster gels
  • Download lecture slides (PDF)

Reading:

  • Slides for now, but Israelachvili chapter 12 is an excellent reference.

Lecture 6

  1. Gel structure under shear
    1. Compaction
    2. Startup of steady shear
    3. Thixotropy
  2. Gels at interfaces
    1. Structure
    2. Interactions
  • Download lecture slides (PDF)

Reading:

  • Slides for now.

Other topics of interest:

  1. Microrheology
    1. Probe-based methods
    2. Continuum and non-continuum limits
    3. Local mechanics of gels
  2. Electrokinetics
    1. zeta-potential
    2. dielectric spectroscopy

List of attached files