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AlessandroPerego_Thesis_Final_2022.pdf (9.46 MB)

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Microscopic dynamics and rheology of vitrimers using hybrid molecular dynamics and Monte Carlo simulations

Perego, Alessandro
http://orcid.org/0000-0002-0570-3210
http://rave.ohiolink.edu/etdc/view?acc_num=akron1659650694358559

Abstract Details

, Doctor of Philosophy, University of Akron, Polymer Engineering.
In contrast to conventional thermosets, vitrimers represent a new class of polymer networks that can exchange covalent bonds and adjust their topology without risking structural damage or permanent loss of material properties above a characteristic topology freezing temperature. This unique feature makes vitrimers perfect candidates to design self-healing polymer materials and improve the lifetime and circularity of plastics. However, due to their novelty, this unique dynamic behavior is not yet fully understood on a molecular level, and there is still a lack of theoretical research on the impact of the lifetime of the exchangeable bonds on the rheology and dynamics of vitrimers. In this study, a combination of coarse-grained molecular dynamics (MD) and Monte Carlo (MC) simulations are used to mimic the thermodynamic, microstructural, and rheological properties of vitrimers. The model captures the two characteristic transition temperatures of vitrimers: conventional glass transition temperature, Tg, and the topology freezing temperature, Tv, used to capture the thermoset-thermoplastic transition. The rheological data accurately describe the main feature of vitrimers, which is the terminal regime of the elastic modulus at low frequencies. Simulations reveal that the lifetime of the exchangeable bonds determines the rheology and dynamics of these networks. When the rate of the deformation is higher than the rate of the bond exchange, the system behaves as a typical thermoset, while at lower rates, the vitrimer behaves as a viscous liquid. The linkage between the microscopic dynamics and the linear rheology of vitrimers is established using the generalized Stokes-Einstein relationship, which efficiently extends the timescale of simulations and predicts the viscoelasticity. Additionally, the values of the shift factors are related to the characteristic decay time of the intermediate scattering function which is accessible in scattering experiments. This work provides a novel simulation methodology to study the linear and nonlinear rheology and mechanics of vitrimers under different operating conditions and with different topologies. The research presented in this work delivers the quantitative means to inverse design these novel materials, which in turn can positively affect the recycling and re-use of the thermosets to create a more circular economy.
Fardin Khabaz (Advisor)
Sadhan Jana (Committee Chair)
Yalin Dong (Committee Member)
Mesfin Tsige (Committee Member)
Kevin Cavicchi (Committee Member)
191 p.
Physics; Political Science
vitrimers, rheology, polymer physics, sustainable polymers

Recommended Citations

Citations

  • Perego, A. (2022). Microscopic dynamics and rheology of vitrimers using hybrid molecular dynamics and Monte Carlo simulations [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1659650694358559

    APA Style (7th edition)

  • Perego, Alessandro. Microscopic dynamics and rheology of vitrimers using hybrid molecular dynamics and Monte Carlo simulations . 2022. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1659650694358559.

    MLA Style (8th edition)

  • Perego, Alessandro. "Microscopic dynamics and rheology of vitrimers using hybrid molecular dynamics and Monte Carlo simulations ." Doctoral dissertation, University of Akron, 2022. http://rave.ohiolink.edu/etdc/view?acc_num=akron1659650694358559

    Chicago Manual of Style (17th edition)

akron1659650694358559
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This open access ETD is published by University of Akron and OhioLINK.