Paper Number
SM3
Session
Polymers Solutions, Melts and Blends
Title
Dynamics of entangled liquid coacervates made from oppositely charged polyelectrolytes
Presentation Date and Time
October 21, 2019 (Monday) 10:40
Track / Room
Track 3 / Room 201
Authors
- Aponte-Rivera, Christian (Duke University, Mechanical Engineering and Materials Science)
- Rubinstein, Michael (Duke University)
Author and Affiliation Lines
Christian Aponte-Rivera and Michael Rubinstein
Mechanical Engineering and Materials Science, Duke University, Durham, NC 27705
Speaker / Presenter
Aponte-Rivera, Christian
Text of Abstract
Mixtures of oppositely charged polyelectrolytes can phase separate to form a polymer rich phase, called a coacervate, and a polymer depleted phase. Much effort has been devoted to understanding the charge-driven phase separation of coacervates made from oppositely charged polyelectrolytes, leading to models that are able to predict the coacervate phase diagram and structure. However, development of models to predict the dynamic properties of coacervates and how these depend on experimentally controllable parameters lags behind. We develop a scaling theory to predict viscoelasticity of and diffusion in entangled charge asymmetric liquid coacervates made from oppositely charged polyelectrolyte solutions. In this work, charge asymmetry results from making a coacervate from polyanions and polycations that have a different line density of charges along their backbones, e.g. a high charge density polyanion and a low charge density polycation. The resulting coacervate has a double-semidilute structure with two correlations lengths – one of the polycation and another of the polyanion. Coacervates can have entangled either only the polyanions, only the polycations or they can have entangled both types of chains. We model entangled coacervates by considering reptation of polymer chains along confining tubes. In unentangled asymmetric coacervates, the different correlation lengths result in a dynamic coupling between the polycation and polyanion, which alters viscosity and diffusion. We predict this dynamic coupling also alters viscosity and diffusion in entangled asymmetric coacervates. Furthermore, we find that the concentration dependence of viscosity and diffusion changes depending on whether the polymer chains are confined to tubes formed by chains of equal or opposite charge in the entangled asymmetric coacervate.