Dynamics and rheology of cyclic polymer melts and solutions
Ring polymers is a special case of chain molecules since they have no ends; as a result they are topologically different than linear counterparts (and/or long chain branched polymers) for which their viscoelasticity is typically described by the reptation theory and variants of the tube model. In addition, it is experimentally believed that the presence of even a small percentage of linear polymers in the ring has a profound effect on their dynamics, causing a significant reduction in their relaxation, thus also on diffusion and viscosity. In an effort to understand the unique rheological properties of ring polymers, we have embarked on a new project involving three steps:
- generation and detailed atomistic molecular dynamics simulations of model polyethylene and polyethylene oxide ring melts (both short and long chain length)
- comparison of simulation results for the chain diffusivity, zero shear rate viscosity, and neutron scattering pattern against similar data from direct experimental measurements
- extension to blends of linear and ring PEO systems – dependence of dynamic properties on blend composition and chain length
- analysis of the simulation results and mapping onto recent theories for entangled rings
- development of methodologies for the topological analysis of ring polymers
- extension to beyond equilibrium conditions by use of non-equilibrium molecular dynamics (NEMD) simulations, in an effort to capture the flow behavior of polymer ring melts which at present is totally unknown