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[摘要]：Polymers undergo a sharp coil stretch transition in extension dominated flows when the strain rate exceeds a critical strain rate We investigate this transition in both Theta solvents and good solvents using Brownian dynamics simulations The polymer is represented by a bead spring chain model undergoing elongational flow and solvent mediated effects such as fluctuating hydrodynamic interactions (HI) and excluded volume (EV) are included rigorously A 1 D energy landscape theory with an activation energy for transition(1) is used to gain qualitative insights into the dynamics A key factor in determining the influence of solvent quality is the use of a proper measure of solvent quality (2 3) Contrary to earlier findings, it is observed that with improvement in solvent quality, the critical strain rate at which the coil to stretch transition takes place decreases Furthermore, the solvent quality has a profound effect on the scaling of the critical strain rate with molecular weight and on both the transient and steady state properties of the system Universal functions are shown to exist for the observed dynamic and static properties, which will prove useful in determining the operating parameters for experiments |
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