Cluster mode-coupling approach to weak gelation in attractive colloids

Area of Science:

• Colloid science
• Soft matter physics
• Theoretical chemistry

Background:

• Mode-coupling theory (MCT) is a key framework for understanding the dynamics and arrest of colloidal systems.
• Colloid aggregation and gelation phenomena present complex dynamics not fully captured by basic MCT.

Purpose of the Study:

• To investigate how cluster aggregation modifies the parameters governing colloid arrest predicted by MCT.
• To model weak gelation as a two-stage ergodicity breaking process.
• To explore the interplay between colloidal arrest and phase separation.

Main Methods:

• Applying MCT to effective parameters that evolve with cluster aggregation.
• Idealizing weak gelation as a two-stage ergodicity breaking process.
• Comparing theoretical predictions with experimental observations.

Main Results:

• Effective MCT parameters evolve under cluster aggregation, influencing colloid arrest.
• Weak gelation is described as a two-stage ergodicity breaking: short-scale (bare MCT) and large-scale (cluster-based MCT).
• A long-lived "semiergodic" phase of mobile clusters with logarithmic relaxation near the gel line is predicted.

Conclusions:

• Cluster aggregation significantly alters colloid dynamics and arrest conditions.
• The two-stage ergodicity breaking model provides a refined understanding of weak gelation.
• The predicted semiergodic phase offers new avenues for experimental investigation in colloidal systems.