Paper Number
GN5                         My Program 

Session
Self-assemblies, Gels and Networks

Title
Simulating surface brush interactions in colloidal gel assembly using angular rigidity

Presentation Date and Time
October 20, 2025 (Monday) 11:10

Track / Room
Track 2 / Sweeney Ballroom B

Authors (Click on name to view author profile)

1. Campbell, Robert (Northeastern University, Mechanical and Industrial Engineering)
2. Haghighi, Paniz (Northeastern University, Mechanical and Industrial Engineering)
3. Zhuang, Calvin (University of California, Irvine, Chemical and Biomolecular Engineering)
4. Mohraz, Ali (University of California, Chemical and Biomolecular Engineering)
5. Jamali, Safa (Northeastern University, Mechanical and Industrial Engineering)

Author and Affiliation Lines (in printed abstract book)
Robert Campbell¹, Paniz Haghighi¹, Calvin Zhuang², Ali Mohraz² and Safa Jamali^1
1Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115; ²Chemical and Biomolecular Engineering, University of California, Irvine, CA 92697

Speaker / Presenter 
Campbell, Robert

Keywords
theoretical methods; computational methods; colloids; gels; networks; selft-assemblies

Text of Abstract

In experiments, model colloidal depletion gels typically rely on a thin polymer brush coating for steric stabilization and the approximation of hard-sphere interactions dominated by depletion. These brush coatings also affect particle charge, changing how electrostatic repulsion can be tuned with added salt. Recent experiments have found that reducing the amount of monomer used to produce this coating not only changes the measured colloidal charge but can also produce unexpectedly fractal gels that arrest at an average contact number ~3 instead of 6. This allows the user to manipulate gel structure and its resulting rheological properties with a single simple change to particle brush synthesis.

We present a companion simulation model that mimics this brush effect with a three-body angular rigidity. Using Brownian dynamics and standard depletion interactions with added electrostatics we allow particles to freely aggregate. When three or more particles form a cluster where brush regions interact, we introduce a non-central angular rigidty to restrict their rearrangement. By adjusting the strength of this rigidity and the range at which it activates we are can tune the resulting gel’s average coordination number below 6. We also demonstrate how the effect of rigidity changes with different depletion and electrostatic conditions. The result is a relatively simple adjustment to traditional simulation methods that can mimic complex brush-brush interactions. We show how this method can represent experimental changes in brush synthesis with minimal information beyond the brushes’ effective charge and approximate length.