Probing Vitrimer Network Dynamics Across Length Scales: From Chain Conformation to Thin-Film Topology Transitions

Author

• Yuming WangFollow

Date of Award

8-2026

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

School

Polymer Science and Engineering

Committee Chair

Zhe Qiang

Committee Chair School

Polymer Science and Engineering

Committee Member 2

Xiaodan Gu

Committee Member 2 School

Polymer Science and Engineering

Committee Member 3

Sergei Nazarenko

Committee Member 3 School

Polymer Science and Engineering

Committee Member 4

Derek Patton

Committee Member 4 School

Polymer Science and Engineering

Committee Member 5

Yoan Simon

Abstract

Vitrimers are an emerging class of covalent adaptable networks that combine the dimensional stability of thermosets with the reprocessability of thermoplastics through associative bond exchange reactions. However, microscopically characterizing vitrimer network dynamics remains challenging, because conventional techniques such as creep, stress relaxation, and rheology often rely on external forces and macroscopic response. These measurements can obscure the intrinsic onset of topology rearrangement and become difficult to interpret in confined, phase-separated, or porous materials. This dissertation addresses this challenge by developing and applying temperature-dependent spectroscopic ellipsometry as a stress-free method to probe vitrimer thermal transitions in thin-film geometries, while also introducing a Forster resonance energy transfer (FRET)-based molecular ruler for measuring polymer chain conformation. The first study establishes ellipsometry as a method for identifying the apparent topology freezing transition temperature (T_v) of vitrimer films by tracking changes in film thickness and apparent thermal expansion behavior as a function of temperature. This approach was validated across catalyst-free disulfide vitrimers, TBD-catalyzed DGEBA-sebacic acid vitrimers, and internally catalyzed benzoxazine-based vitrimers, demonstrating that the apparent changes in thermal expansion behavior of vitrimer films arise from relaxation kinetics instead of thermodynamic free volume variations. The second study expands this ellipsometric approach to confined vitrimer thin films, phase-separated vitrimer/polystyrene blends, and porous vitrimer networks. In both DGEBA-sebacic acid and 4-AFD/PEGDGE vitrimer films, decreasing film thickness significantly shifts the glass transition temperature (T_g), while the apparent T_v remains nearly unchanged, indicating that segmental mobility is more sensitive to confinement than bond-exchange-mediated topology rearrangement. In phase-separated vitrimer blends, ellipsometry resolves phase-specific T_g values and a distinct apparent T_v within a single heating-cooling cycle, while porous vitrimer films show densification above T_v due to dynamic network rearrangement. Finally, this dissertation develops a FRET-based method using an anthracene-functionalized Reversible Addition Fragmentation Chain Transfer (RAFT) chain-transfer agent to directly synthesize donor-acceptor-labeled polystyrene and poly (methyl methacrylate). The resulting FRET-derived chain-end-to-end distances agree well with molecular dynamics simulations, confirming the accuracy of this approach. Together, these studies establish ellipsometry and FRET as complementary tools for probing vitrimer network dynamics and chain conformation across length scales.

Copyright

Yuming Wang

Recommended Citation

Wang, Yuming, "Probing Vitrimer Network Dynamics Across Length Scales: From Chain Conformation to Thin-Film Topology Transitions" (2026). Dissertations. 2489.
https://aquila.usm.edu/dissertations/2489