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

Particle shape and surface roughness may have synergistic effects on particle network formation in colloidal gels. Particles with an aspect ratio greater than one have orientation-dependent interactions with neighboring particles compared to spheres, making their interactions highly sensitive to rotational dynamics. By adding surface roughness, we add non-central surface forces and expect to further constrain particle rotation, potentially enhancing the stability and rigidity of networks formed by these particles.

To this end, smooth and rough particles of different aspect ratios were synthesized and grafted with an octadecyl layer to form a thermoreversible gel in tetradecane. The gels were characterized using rheological and optical methods.

Surface roughness was found to reduce the percolation threshold and improve sedimentation stability, though its impact diminishes with increasing aspect ratio. Rough particles formed more homogeneous networks, as surface roughness restricts the excluded-volume-driven local alignment in smooth systems. Consequently, elasticity and yielding behavior are more strongly influenced by aspect ratio in smooth rod gels than in rough rod gels.