Spatially Correlated Dynamics in a Simulated Glass-Forming Polymer Melt: Analysis of Clustering Phenomena

Published

November 1, 2001

Author(s)

Y Gebremichael, T B. Schroder, Francis W. Starr, S C. Glotzer

Abstract

In recent years, experimental and computational studies have demonstrated that the dynamics of glass-forming liquids are spatially heterogeneous, exhibiting regions of temporarily enhanced or diminished mobility. Here we present a detailed analysis of dynamical heterogeneity in a simulated bead-spring'' model of a low molecular-weight polymer melt. We investigate the transient nature and size distribution of clusters of mobile'' chain segments (monomers) as the polymer melt is cooled towards its glass transition. We also explore the dependence of this clustering on the definition of mobility. We show that the mean cluster size is time dependent with a peak at intermediate time, and that the mean cluster size at the peak time grows with decreasing temperature. The growing size of the clusters demonstrates the growing range of correlated motion, previously reported for this same system. The distribution of cluster sizes approaches a power law near the mode coupling temperature, similar to behavior reported for a simulated binary mixture and a dense colloidal suspension, but with a different exponent. We calculate the correlation length of the clusters, and show that it exhibits similar temperature and time-dependent behavior as the mean cluster size, with a maximum at intermediate time.

Citation

Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)

Volume

64

Issue

No. 5

Pub Type

Journals

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Keywords

clustering, correlation length, glass transition, molecular dynamics, polymer melt, simulations

Citation

Gebremichael, Y. , Schroder, T. , Starr, F. and Glotzer, S. (2001), Spatially Correlated Dynamics in a Simulated Glass-Forming Polymer Melt: Analysis of Clustering Phenomena, Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851880 (Accessed December 21, 2024)