Paper Number
SM14 

Session
Polymer Solutions and Melts

Title
Stretch-relaxation of DNA molecules in semidilute solutions

Presentation Date and Time
October 12, 2015 (Monday) 5:15

Track / Room
Track 2 / Constellation D

Authors (Click on name to view author profile)

1. Sasmal, Chandi (Monash University, Chemical Engineering)
2. Kai-Wen, Hsiao (University of Illinois at Urbana-Champaign, Chemical & Biomolecular Engineering)
3. Schroeder, Charles M. (University of Illinois at Urbana-Champaign, Chemical & Biomolecular Engineering)
4. Prakash, J. Ravi (Monash University, Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
Chandi Sasmal¹, Hsiao Kai-Wen², Charles M. Schroeder², and J. Ravi Prakash^1
1Chemical Engineering, Monash University, Melbourne, Victoria 3150, Australia; ²Chemical & Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801

Speaker / Presenter 
Sasmal, Chandi

Text of Abstract
Single molecule techniques have been used to directly observe the dynamics of fluorescently labelled linear semi-flexible DNA molecules in the semidilute concentration regime, subjected to planar extensional flow in a microfluidic cross-slot cell. Until recently, these methods have largely been confined to observations of DNA molecules in the ultra dilute limit. We study the conformational and stretching dynamics of DNA chains, and the relaxation following cessation of flow, as a function of concentration and Weissenberg number. Experimental observations have been complemented with numerical simulations, carried out with a computationally efficient multi-chain Brownian dynamics algorithm, which is capable of simulating polymer solutions at finite concentrations, and in which Kraynik-Reinelt periodic boundary conditions have been implemented to simulate planar extensional flow. A worm-like bead-spring chain model, with excluded-volume and hydrodynamic interactions taken into account, is used to represent DNA molecules. The successive fine graining technique, in which simulation data is accumulated for chains with increasing numbers of beads, N, and then extrapolated to the limit N → N_K (where N_K is the number of Kuhn steps), has been used to carry out a parameter-free comparison of experimental observations with numerical simulations. We observe that polymers in the semidilute regime exhibit key differences in dynamics compared to dynamics in the dilute regime. This work extends the field of single polymer dynamics to semidilute solutions, and addresses important questions in classical polymer physics on chain dynamics at the molecular level in this concentration regime.