Paper Number
SM48 

Session
Polymer Solutions and Melts

Title
Size, shape and diffusivity of a single Debye-Hückel polyelectrolyte chain in solution

Presentation Date and Time
October 15, 2015 (Thursday) 9:30

Track / Room
Track 2 / Constellation D

Authors (Click on name to view author profile)

1. Soysa, W. Chamath (Monash University, Chemical Engineering)
2. Duenweg, Burkhard (Max Planck Institute for Polymer Research)
3. Prakash, J. Ravi (Monash University, Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
W. Chamath Soysa¹, Burkhard Duenweg², and J. Ravi Prakash^1
1Chemical Engineering, Monash University, Melbourne, Victoria 3150, Australia; ²Max Planck Institute for Polymer Research, Mainz, Germany

Speaker / Presenter 
Prakash, J. Ravi

Text of Abstract
Brownian dynamics simulations of a coarse-grained bead-spring chain model, with Debye-Hückel electrostatic interactions between the beads, are used to determine the root-mean-square end-to-end vector, the radius of gyration, and various shape functions (defined in terms of eigenvalues of the radius of gyration tensor) of a weakly-charged polyelectrolyte chain in solution, in the limit of low polymer concentration. The long-time diffusivity is calculated from the mean square displacement of the centre of mass of the chain, with hydrodynamic interactions taken into account through the incorporation of the Rotne-Prager-Yamakawa tensor. Simulation results are interpreted in the light of the OSFKK blob scaling theory which predicts that all solution properties are determined by just two scaling variables—the number of electrostatic blobs X, and the reduced Debye screening length, Y. We identify three broad regimes, the ideal chain regime at small values of Y, the blob-pole regime at large values of Y, and the crossover regime at intermediate values of Y, within which the mean size, shape, and diffusivity exhibit characteristic behaviours. In particular, when simulation results are recast in terms of blob scaling variables, universal behaviour independent of the choice of bead-spring chain parameters, and the number of blobs X, is observed in the ideal chain regime and in much of the crossover regime, while the existence of logarithmic corrections to scaling in the blob-pole regime leads to non-universal behaviour. With the inclusion of the characteristic shear rate β􏰉 as the additional scaling variable in shear flow, the equilibrium blob model provides a framework to obtain parameter free data collapse, even for rheological properties.