Viscoelasticity of vitrimers: tunability and applications of dynamic networks

Porath, Laura Elizabeth Gowlovech

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

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

Copyright and License Information

Copyright 2022, Laura Porath

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