Paper Number
VP18 

Session
Pre-recorded Flash Presentations (virtual)

Title
Linear viscoelasticity of associating star polymer networks

Presentation Date and Time
All Week (Asynchronous) Any Time

Track / Room
Pre-recorded Presentation / Virtual

Authors (Click on name to view author profile)

  1. Robe, Dominic M. (Monash University, Department of Chemical Engineering)
  2. McKinley, Gareth H. (Massachusetts Institute of Technology, Mechanical Engineering)
  3. Prakash, J. Ravi (Monash University, Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
Dominic M. Robe1, Gareth H. McKinley2 and J. Ravi Prakash1
1Chemical Engineering, Monash University, Clayton, Victoria 3800, Australia; 2Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA

Speaker / Presenter 
Robe, Dominic M.

Keywords
computational methods; gels; polymer solutions

Text of Abstract
We present an analysis of the linear viscoelastic behaviour of associating star polymers using a multi-chain Brownian dynamics simulation algorithm that incorporates hydrodynamic interactions. By attaching functional groups that can reversibly bond at the end of each arm of a four-arm star polymer it is possible to create almost ideal viscoelastic gels. Experimental work by Parada & Zhao [1] has demonstrated that such a system can behave as a simple Maxwell material over a range of pH and temperatures. They propose a microscopic network theory model to explain this behaviour which our simulations can observe directly. Critical to the model is the concentration of elastically-active arms, which determines the instantaneous shear modulus. We analyse microscopic trajectories from Brownian dynamics simulations to independently measure the concentration of elastically-active arms and the resulting shear modulus. The model of Parada & Zhao also shows a dependence of the material’s relaxation time on the dissociation rate of the stars. Our algorithm allows us to set the well depth in the associative interactions and measure the bond dissociation rate independently from the relaxation time. Through these observations we validate the model of Parada & Zhao and determine the range of system parameters such as concentration and molecular weight over which the model holds. The linear viscoelastic storage and loss moduli of these networks of stars are also computed dynamically as functions of association strength and concentration and compared with results from experiment.
[1] G. A. Parada, X. Zhao, Soft Matter, 14, 5186-5196 (2018).