Mechanically interlocked polymers (MIPs) are a novel class of polymer structures in which the components are connected by mechanical bonds instead of traditional covalent bonds. We investigate the rheological properties of polyrotaxanes, daisy chains, and polycatenanes under steady shear and extensional flow using coarse-grained Brownian dynamics simulations with hydrodynamic interactions. We study key polymer behaviors, including tumbling dynamics, molecular extension, and viscosity. Our results show that topological bonds significantly influence polymer dynamics. Compared with linear polymers, all three MIPs exhibit enhanced tumbling in shear flow. While polyrotaxanes show higher viscosity and normal stress differences, polycatenanes and daisy chains have lower viscosities and normal stress differences than a linear chain. In extensional flow, polyrotaxanes and polycatenanes extend earlier than linear polymers. We show that the key properties of these MIPs stem from the mechanically bonded rings in their structure, which expand the polymer profile in gradient direction and increase backbone stiffness due to repulsive interactions. This study provides key insights into MIP flow properties, paving the way for their development in advanced materials/novel applications.
