(257e) Linear Viscoelasticity of Nanocolloidal Suspensions from Rotating Probe Rheology Simulations

Probe rheology technique gives the ability to determine the local viscoelastic properties of materials which is useful for highly heterogeneous systems. Typical implementation of probe rheology involves inferring the viscoelastic modulus values by tracking the translational motion of the probe particles. Rotational motion of the probe particle is even more localized and causes less disturbance than the translational motion of the probe particles. In this work, rotating probe rheology method is implemented in conjunction with molecular dynamics (MD) simulations to measure the linear viscoelastic properties of nanocolloidal suspensions. Rotating probe rheology molecular simulations are performed on two colloidal suspensions with volume fractions of 0.35 and 0.40 to determine the linear viscoelastic properties of these systems. By using continuum theory to analyze the oscillatory rotational motion of the probe particle, the viscoelastic modulus of the suspensions is obtained. In the linear regime, distribution of colloidal particles around the probe is symmetric. The dynamic modulus values obtained from simulations are in good agreement with the results from the oscillatory nonequilibrium MD (NEMD) technique and previous probe rheology simulations that involved translational motion of the probe particles [D. Sundaravadivelu Devarajan and R. Khare, J. Rheol. 66, 837–852 (2022)]. At higher volume fractions, rotational probe rheology simulation results are in good agreement with those from NEMD results only when the probe particle is much larger than the colloidal particles.