Paper Number
SR8 

Session
Sustainable and Recyclable Polymers

Title
Effects of crosslinking density and salt addition on viscoelasticity and conductivity of vinylogous urethane (VU)-based ionic dynamic polymer network

Presentation Date and Time
October 10, 2022 (Monday) 1:50

Track / Room
Track 4 / Michigan AB

Authors (Click on name to view author profile)

  1. Jang, Seongon (University of Illinois at Urbana-Champaign, Materials Science and Engineering)
  2. Schroeder, Charles M. (University of Illinois at Urbana-Champaign, Chemical and Biomolecular Engineering)
  3. Evans, Christopher M. (University of Illinois Urbana Champaign, Materials Science and Engineering)

Author and Affiliation Lines (in printed abstract book)
Seongon Jang1, Charles M. Schroeder2 and Christopher M. Evans1
1Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana-Champaign, IL 61801; 2Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801

Speaker / Presenter 
Jang, Seongon

Keywords
polymer sustainability; recyclable polymers

Text of Abstract
Dynamic covalent polymer networks with a topology-conserving bond exchange mechanism (known as vitrimers) are emerging materials replacing conventional polymers due to their recyclability and self-healing properties. Vitrimers are of key interest in applications such as electrolytes where the self-healing and conductivity are controlled by salt addition. In this work, vinylogous urethane (VU)-based vitrimers containing Li salts were prepared with different crosslinking densities using precise linker lengths of ethylene glycol (EG). Stress relaxation experiments show that the ionic dynamic networks exhibited substantially faster relaxation (i.e., smaller relaxation times) compared to neutral networks. Moreover, these materials exhibited an Arrhenius temperature dependence as expected for vitrimers where flow is controlled by bond exchange reactions that obey an Arrhenius temperature dependence. In addition, relaxation times and shear moduli were found to decrease as the crosslinking density decreases. Electrochemical impedance spectroscopy was performed to investigate ionic charge transport depending on mesh sizes of the network. As expected, ionic conductivity increases as the linker length increases. The conductivity was normalized by glass transition temperature (Tg) revealing a universal plot as a function of Tg/T, indicating that ionic charge transport is primarily controlled by the segmental dynamics of EG chains. 7Li ssNMR suggests that dynamic networks with longer linker lengths prefer Li-EO coordination rather than Li-VU coordination based on chemical shifts. Overall, this work provides an improved understanding of ionic dynamic polymer networks, which is essential for applications involving solid polymer electrolytes.