Date/Time
Date(s) - 09/24/2024
3:00 pm - 4:00 pm
Location
Rhines 125
Categories
Abstract
A vitrimer is a polymer network with dynamic covalent cross-links that engage in an associative exchange, i.e., new bonds form before old linkages break. The associative cross-links maintain network connectivity while allowing topology changes, making vitrimers insoluble yet processable at high temperatures. While these paradoxical traits make vitrimers potentially useful for enhancing polymer sustainability, the relationship between their molecular structure and macroscopic viscoelasticity remains an open question.
Here, we use a combination of theory and experiment to illuminate structure-viscoelasticity relationships for unentangled vitrimer melts. First, we develop a generalized inhomogeneous Rouse model (IHR) that accounts for interactions between relaxation modes of the regular backbone monomers and associative cross-links. Using the IHR to evaluate the effect of molecular structure and temperature, two distinct relaxation regimes are identified: (I) segmental motions of the backbone at short times and (II) network strand relaxation and cross-link exchange at long times. Next, we experimentally evaluate the viscoelasticity of polybutadiene vitrimers with dioxaborolane cross-links (glass transition temperature Tg < 0 °C) and polystyrene vitrimers with imine cross-links (Tg > 100 °C). The rheological behaviors are compared to the IHR predictions to gauge the impact of molecular structure and temperature on vitrimer relaxation.
Bio
Ralm Ricarte, Ph.D.
Assistant Professor
Florida A&M – Florida State University College of Engineering
Dr. Ralm Ricarte is an Assistant Professor at the Florida A&M University-Florida State University College of Engineering. He earned a BS in Chemical Engineering from The University of Texas at Austin and a Ph.D. in Chemical Engineering from the University of Minnesota. After his doctorate, he served as a Marie Curie and PRESTIGE Postdoctoral Fellow at ESPCI Paris. His laboratory investigates the influence of molecular structure on dynamic polymer networks, with a specific focus on vitrimers and polymerization-induced self-assembly. To study these complex systems, his laboratory employs a combination of synthesis, characterization, and theoretical modeling techniques.
Dr. Ricarte has earned several honors throughout his career, including the NSF CAREER Award, 3M Non-Tenured Faculty Award, and Florida State University Honors Thesis Mentor Award.