Local swelling effect of flexible entangled polymer chains in athermal solvents

JY Wang and P Gao, PHYSICS OF FLUIDS, 36, 032024 (2024).

DOI: 10.1063/5.0194761

Solutions of flexible, entangled polymer chains dissolved in athermal solvents have been widely studied; however, the influence of the local swelling effects on the overall dynamics of such systems remains incompletely understood. In this study, we performed coarse-grained simulations to compute the concentration dependence of plateau modulus of such systems. Initially, we examined the concentration dependence of entanglement length, denoted as N-e, through simulations. Our findings revealed a concentration scaling relationship for Ne, demonstrating N-e = A Phi(-5/4) + B, where A and B are chain length independent constants, and Phi is polymer concentration. To account for the local swelling effects, we employed the concept of blobs to represent the chains confined in athermal solvents. Each blob was characterized by a diameter xi, a number of connected beads g, and a volume Omega(b) similar to xi(3). Our simulations showed that the blob diameter followed the excluded volume relationship, with xi similar to g(3/5). By combining the local swelling effect and the non-zero constant B, we derived a concentration scaling relationship for the plateau modulus G of solutions of flexible polymer chains in athermal solvents: G similar to Phi/(N-e/g)Omega(b) similar to Phi(2.30). This scaling exponent aligns with experimental observations ranging from dilute to highly concentrated systems, as well as our simulations, where values of 2.0-2.3 were observed.

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