University of Illinois Urbana-Champaign

Viscoelasticity of vitrimers: tunability and applications of dynamic networks

Porath, Laura Elizabeth Gowlovech

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PORATH-DISSERTATION-2022.pdf

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https://hdl.handle.net/2142/115464

Description

Title
Viscoelasticity of vitrimers: tunability and applications of dynamic networks
Author(s)
Porath, Laura Elizabeth Gowlovech
Issue Date
2022-04-21
Director of Research (if dissertation) or Advisor (if thesis)
Evans, Christopher M
Doctoral Committee Chair(s)
Evans, Christopher M
Committee Member(s)
  • Sottos, Nancy
  • Ewoldt, Randy H
  • Statt, Antonia
Department of Study
Materials Science & Engineerng
Discipline
Materials Science & Engr
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
  • vitrimers
  • dynamic polymer networks
  • rheology
  • viscoelasticity
  • vibration damping
  • ultra thin coating
  • self-healing
Abstract
Vitrimers are a type of self-healing polymer that have dynamic covalent associative bonds. Associative bonds, unlike dissociative bonds, do not break the network integrity during the exchange process, and therefore have no loss in network properties. Due to their dynamic nature, vitrimers experience viscoelasticity, or the ability to have both liquid (viscous) and solid (elastic) properties on different timescales. The rheology, which is the measure of how things flow, for these dynamic polymers is profoundly different from permanent polymers and melts. Vitrimers experience Arrhenius behavior of relaxation time or viscosity versus temperature, whereas typical polymers exhibit a steep increase in viscosity upon approaching the glass transition temperature. Due to their ability to self-heal and remain processable over a much wider temperature range, vitrimers are ideal for many applications including 3D printing, adhesives, battery electrolytes, energy dissipation, drug delivery carriers, and coatings. This work focuses on vitrimers of polydimethylsiloxane backbone crosslinked with various boronic esters. First, the rheological techniques for these materials are discussed with both oscillatory shear and step stress experiments providing similar relaxation times in vitrimers of sufficiently high molecular weight. Then, crosslinkers with different kinetics are studied independently and mixed in the PDMS vitrimers in an effort to design multi-modal relaxation spectra for vibration damping. The mixed networks follow the viscoelastic properties of their faster component and do not show multiple peaks. Due to the hydrophobic and dynamic behavior PDMS vitrimers, these materials were made into ultra-thin vitrimer coatings, which were able to self-heal abrasions and withstand condensation for weeks. Investigating the viscoelastic properties of the PDMS vitrimers while systematically tuning their chemistry has led to better understanding of dynamic materials and the design of successful materials for applications.
Graduation Semester
2022-05
Type of Resource
Thesis
Handle URL
https://hdl.handle.net/2142/115464
Copyright and License Information
Copyright 2022, Laura Porath

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