Paper Number
SR7 

Session
Sustainable and Recyclable Polymers

Title
Design of multimodal relaxation in recyclable acrylate vitrimers with multiple dynamic bonds

Presentation Date and Time
October 10, 2022 (Monday) 1:30

Track / Room
Track 4 / Michigan AB

Authors (Click on name to view author profile)

  1. Porath, Laura E. (University of Illinois Urbana Champaign, Materials Science and Engineering)
  2. Ramlawi, Nabil (University of Illinois Urbana Champaign, Mechanical Science and Engineering)
  3. Ewoldt, Randy H. (University of Illinois at Urbana-Champaign, Mechanical Science and Engineering)
  4. Evans, Christopher M. (University of Illinois Urbana Champaign, Materials Science and Engineering)

Author and Affiliation Lines (in printed abstract book)
Laura E. Porath1, Nabil Ramlawi2, Randy H. Ewoldt2 and Christopher M. Evans1
1Materials Science and Engineering, University of Illinois Urbana Champaign, Urbana, IL 61802; 2Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801

Speaker / Presenter 
Porath, Laura E.

Keywords
polymer sustainability; recyclable polymers

Text of Abstract
Peaks in the relaxation spectrum of a polymer lead to damping behavior of sound and vibrations. By designing the placement, breadth, and height of the relaxation modes, ideal damping materials can be created. Dynamic bonds in polymer networks have shown promise for imparting peaks in the relaxation spectra, however the design rules are not well understood. Our previous work has shown that telechelic PDMS vitrimers (associative dynamic networks) end crosslinked with mixed boronic esters having four orders of magnitude different exchange rates do not exhibit multimodal relaxation. Here, statistically crosslinked acrylate polymers are synthesized with mixed dynamic crosslinks of the same boronic esters. Oscillatory shear rheology shows an acrylate network with one crosslinker exhibits Maxwell behavior typical of a rubbery network, including a crossover of G’ and G” from which we obtain the relaxation time. Acrylate networks with mixed fast and slow crosslinkers demonstrate a rubbery plateau, critical gel region (characterized by a power law of both G’ and G”), and a terminal regime in a single frequency sweep. The mixed network also shows two relaxation modes in the stress relaxation curve. The critical gel region grows in breadth and the two relaxation modes become further separated upon heating which is attributed to the distinct temperature dependences of the fast and slow bonds. While the relaxation times of the pure networks differ by 2-3 orders of magnitude, the moduli of all of the networks approach similar plateau values, providing independent control of viscoelastic properties. By systematically probing the chemical origins of multimodal behavior in dynamic networks and investigating with multiple rheological techniques, a highly tunable and recyclable material has been developed for many applications.