Paper Number
SM2 

Session
Polymers Solutions, Melts, and Blends

Title
Rouse model with fluctuating internal friction

Presentation Date and Time
October 11, 2021 (Monday) 10:15

Track / Room
Track 1 / Ballroom 5

Authors (Click on name to view author profile)

  1. Kailasham, Ramalingam (IITB-Monash Research Academy)
  2. Chakrabarti, Rajarshi (Indian Institute of Technology Bombay, Department of Chemistry)
  3. Prakash, J. Ravi (Monash University, Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
Ramalingam Kailasham1, Rajarshi Chakrabarti2 and J. Ravi Prakash3
1IITB-Monash Research Academy, Mumbai, Maharashtra 400076, India; 2Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Maharashtra 400076, India; 3Chemical Engineering, Monash University, Clayton, Victoria 3800, Australia

Speaker / Presenter 
Kailasham, Ramalingam

Keywords
theoretical methods; computational methods; non-Newtonian fluids; polymer solutions

Text of Abstract
Macromolecules in solution experience an additional mode of dissipation due to intramolecular interactions, over and above the solvent drag, which resists their conformational reconfiguration. This additional mode of dissipation termed as internal friction [1], has been known to significantly affect the conformational dynamics of chains [2] and the rheology of polymer solutions [3]. Coarse-grained polymer models for internal friction include a dashpot, in parallel with the spring, which captures the resistive force proportional to the time-rate of change of the connector vector between the beads. An exact solution to this model has so far been unavailable, except for the simplest case of a dumbbell, due to the coupling of bead velocities. By expanding the scope of an existing methodology [3] for velocity-decoupling, the exact set of governing stochastic differential equations for a bead-spring-dashpot chain with more than two beads, and its numerical solution using Brownian dynamics, is presented for the first time. This solution is used to: (a) obtain predictions for material functions in simple and oscillatory shear-flow, and (b) address the importance of fluctuations in modeling internal friction, given that the most widely used theoretical framework [4] for interpreting the effects of internal friction in biomolecules relies on a preaveraged treatment of the phenomenon. The inclusion of internal friction results in a non-monotonous variation of the viscosity with shear rate, with the occurrence of continuous shear-thickening following an initial shear-thinning regime. Furthermore, the neglect of fluctuations in internal friction is found to have consequences both at equilibrium and in the presence of a flow-field.

[1] C. W. Manke and M. C. Williams, Macromolecules 18, 2045 (1985).
[2] A. Soranno et al., Proc. Natl. Acad. Sci. U.S.A. 109, 17800 (2012).
[3] C. W. Manke and M. C. Williams, J. Rheol. 31, 495 (1988).
[4] B. S. Khatri and T. C. B. McLeish, Macromolecules 40, 6770 (2007).