Effect of threading on static and dynamic properties of polymer chains in entangled linear-ring blend systems with different stiffness

Abstract

Threading is a unique topological state in linear/ring polymer blends (LRB), which is considered to be essential for evaluating both the static and dynamic properties of ring polymer (RP)-containing polymer melts. In the present work, we use molecular dynamics simulations with the Kremer-Grest model to systematically investigate the threading event and its effect on the properties of RP in linear polymer (LP) dominated LRB. The chain stiffness is also considered in the simulation to represent a wider range of polymer systems. To obtain the exact number of threads for each RP chain, the inner minimal surface (IMS) technique is applied. We find that for a wide range of chain lengths, the number of threads can be roughly estimated using the predetermined entanglement number for RP chains with different stiffness. The number of threads follows a Gaussian distribution, and the width increases monotonically for longer and stiffer chains. The effect of threading on both the size and shape of RP chains is investigated. We find that for RP chains of different chain lengths, the effect of threading on polymer size is more pronounced for more flexible chains. The effect of threading on shape of RP is also enhanced for longer chains, but the sensitivity of the shape to threading is indistinguishable for RP chains of different stiffness. The dynamics of threading is also studied in this work, and a much slower relaxation time is found for more flexible chains. In conclusion, we have developed a method that can directly detect the threading events in LRB, which allows us to quantitatively study the effect of threading. The result obtained by this method is also expected to be integrated into the viscoelastic theory to better estimate the rheological properties of LRB systems.