Slow dynamics in dense oil-water emulsions studied using dynamic light scattering

Area of Science:

• Colloid and surface science
• Soft matter physics
• Materials science

Background:

• Turbid and concentrated colloidal systems exhibit complex dynamics, including slow dynamics and ageing.
• Traditional light scattering techniques struggle with multiple scattering and slow dynamics in such systems.
• The flat cell geometry offers advantages in transmission and reduced multiple scattering.

Purpose of the Study:

• To introduce and characterize the novel 3D-echo-dynamic light scattering flat cell instrument (3D-echo-DLS-FCLSI).
• To investigate the ageing behavior and confinement effects in dense fluids within a flat cell.
• To compare glass transition measurements using the 3D-echo-DLS-FCLSI with complementary methods.

Main Methods:

• Combines modified 3D-dynamic light scattering (3D-DLS) for multiple scattering suppression with echo-DLS for slow dynamics measurement.
• Utilizes a flat cell light scattering instrument (FCLSI) to enhance transmission and minimize multiple scattering.
• Employs complementary methods, such as multispeckle light scattering, for specific property measurements like heterogeneity.

Main Results:

• The 3D-echo-DLS-FCLSI successfully measures slow dynamics in turbid and concentrated colloidal systems.
• Ageing behavior in dense fluids is significantly influenced by the cell filling process.
• Comparison with multispeckle instrument confirms alpha-relaxation in the glassy state of an index-matched emulsion.

Conclusions:

• The 3D-echo-DLS-FCLSI is a powerful tool for studying slow dynamics and ageing in dense colloidal systems.
• Confinement effects and filling procedures play crucial roles in the observed ageing phenomena.
• The instrument provides valuable insights into the glass transition and relaxation dynamics in complex fluids.