Projection of atomistic simulation data for the dynamics of entangled polymers onto the tube theory: calculation of the segment survival probability function and comparison with modern tube models

作     者：Stephanou, Pavlos S. Baig, Chunggi Mavrantzas, Vlasis G. 

作者机构：Univ Patras Dept Chem Engn GR-26504 Patras Greece FORTH ICE HT GR-26504 Patras Greece 

出 版 物：《SOFT MATTER》 (软物质)

年 卷 期：2011年第7卷第2期

页      面：380-395页

核心收录：

学科分类：081704[工学-应用化学] 07[理学] 070304[理学-物理化学(含∶化学物理)] 08[工学] 0817[工学-化学工程与技术] 0805[工学-材料科学与工程（可授工学、理学学位）] 0703[理学-化学] 0702[理学-物理学] 

基　　金：European Commission [FP7-NMP-2008-SMALL-2] National Science Foundation (USA) [CBET-0742679] 

主　　题：flow field dynamics Polymer melts Probability functions simulated data Autocorrelation function 

摘      要：State-of-the-art tube models for the dynamics of entangled polymer melts are usually validated on the basis of the agreement of their predictions for the linear viscoelastic properties (LVE data) of the system against experimentally measured data. We present here a more direct and fundamental test of these models based on their comparison against molecular dynamics (MD) simulation data for the dynamics of primitive paths (PPs) in the system under study. More precisely, we show how one can take advantage of a recently developed computational methodology (P. S. Stephanou, C. Baig, G. Tsolou, V. G. Mavrantzas and M. Kroger, J. Chem. Phys., 2010, 132, 124904) for calculating the most important function of all tube models, the segment survival probability psi(s, t) and its average Psi(t) (the overall tube survival probability), by projecting MD data of atomistically detailed samples onto the level of the primitive paths, to directly probe mechanisms proposed for chain relaxation, such as contour length fluctuation (CLF) and constraint release (CR). The simulation data for psi(s, t) and Psi(t) can be used next to evaluate refinements of the original Doi-Edwards reptation theory based on a modified diffusion equation for psi(s, t) incorporating the terms proposed to account directly or indirectly for these effects (CLF and CR). The functions psi(s, t) and Psi(t) determined directly from the atomistic MD simulation data account automatically for all these relaxation mechanisms, as well as for any other mechanism present in the real melt. We present and discuss results from such an approach referring to model, strictly monodisperse cis- and trans-1,4-polybutadiene and polyethylene melts containing on average up to 6 entanglements per chain, simulated in full atomistic detail for times up to a few microseconds (that is, comparable to the chain disentanglement time tau(d)). From the same simulations we also present results for two other measures of the PP dynamics in the frame