Date of Award

Spring 5-16-2025

Document Type

Thesis

Degree Name

Master of Science in Chemistry (MSChem)

Department

Chemistry

First Advisor

Dr. Ram K. Gupta, [email protected]

Second Advisor

Dr. Timothy Dawsey, [email protected]

Third Advisor

Dr. Alessandro Martins, [email protected]

Keywords

Covalent Adaptable Network, Smart Thermoset, Epoxy Resin, GME, Dynamic covalent bonds, Bio-based Polymer

Abstract

Covalent Adaptable Networks (CANs) are a pioneering family of polymers that have garnered significant attention in recent years and are characterized by covalent crosslinks that exhibit reversible dynamic alterations by external stimuli. Additionally, unlike traditional thermosets, CAN’s especially vitrimers, offer a range of properties such as self-healing, reprocessability, shape-memory, and recycling capabilities due to the dynamic feature of covalent crosslinks. Recently, an increasing trend in the global production of thermosets involves rapid consumption of petroleum-based resources, which has become a growing environmental concern. From this perspective, the development of eco-friendly thermosets from bio-based feedstocks is a possible way to overcome these drawbacks. In this context, geraniol is one of the monoterpenoid alcohols, a primary component of several plant oils that become a valuable replacement for petroleum-based resources. In this study, for the first time, a geraniol-derived epoxy vitrimer has been developed by a thermally triggered “thiol-epoxy click” reaction between the geraniol-based epoxy resin and dynamic diboronic ester dithiol (DBDT) cross-linker. The resulting vitrimer exhibits excellent self-healing properties driven by the topology alteration through the dynamic transesterification of boronic ester bonds. The fabricated epoxy vitrimers possess superior thermal stability and significant mechanical properties with the absolute value of glass transition temperature (Tg) of 38.43°C determined from DMA analysis. Incorporating dynamic boronic ester linkages imparts an enhanced tensile strength of ~19 MPa, enabling the vitrimer to recover its original shape after deformation (shape memory), solvent recycling ability, and excellent reprocessability with the maximum restoration of mechanical strength. Moreover, the vitrimer was further characterized by a remarkably short relaxation time of 9 s at 140°C and an activation energy of 22.44 kJ/mol. In a nutshell, the developed vitrimer demonstrates significant potential for use in various commercial sectors, and its reversible bond-breaking-making ability under specific conditions offers new opportunities for developing sustainable, high-performance materials.

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