Tuning particle aspect ratio and surface roughness to modulate properties in colloidal gels

Area of Science:

• Colloid and Polymer Science
• Materials Science
• Soft Matter Physics

Background:

• Particle shape and surface roughness influence colloidal gel network formation.
• Non-spherical particles exhibit orientation-dependent interactions, sensitive to rotational dynamics.
• Surface roughness can introduce non-central forces, potentially constraining particle rotation and enhancing network stability.

Purpose of the Study:

• To investigate the synergistic effects of particle shape (aspect ratio) and surface roughness on colloidal gel formation and properties.
• To determine how surface roughness impacts particle network homogeneity, stability, and mechanical response.
• To elucidate the role of constrained rotation in the behavior of anisotropic colloidal gels.

Main Methods:

• Synthesis of smooth and rough particles with varying aspect ratios.
• Grafting particles with an octadecyl layer to form thermoreversible gels in tetradecane.
• Characterization of gel properties using rheological and optical techniques.

Main Results:

• Surface roughness reduced the percolation threshold and improved sedimentation stability of colloidal gels.
• The effect of surface roughness on stability diminished with increasing particle aspect ratio.
• Rough particles yielded more homogeneous networks by restricting excluded-volume-driven alignment.
• Elasticity and yielding behavior were more sensitive to aspect ratio in smooth rod gels compared to rough rod gels.

Conclusions:

• Surface roughness significantly enhances colloidal gel stability and homogeneity, particularly for lower aspect ratio particles.
• Constrained particle rotation due to surface roughness alters network formation and mechanical properties.
• The interplay between particle shape and surface texture is crucial for designing robust colloidal materials.