Low Tc Thiolactone Monomers for Chemically Recyclable Polythioesters
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Stellmach, Kellie Anne
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Abstract
The growing demand for sustainable materials has led to increased interest in monomers that can undergo chemical recycling to monomer (CRM), enabling the full depolymerization and remanufacturing of plastics with no loss in material properties. This thesis investigates thiolactone monomers as promising candidates for CRM due to their favorable polymerization thermodynamics and efficient depolymerization pathways. Structural modifications, including methyl substitution and sulfur incorporation, were explored to modulate the enthalpy (ΔHp) and entropy (ΔSp) of polymerization, and ceiling temperatures (Tc). Variable-temperature NMR and computational studies revealed how ring strain and conformation influence the polymerization thermodynamics. Additionally, a comprehensive analysis of thermodynamic pitfalls was performed using Me₂-DTN as a model system, leading to improved best practices for accurately determining Tc. Finally, this work demonstrates the synthesis of chemically recyclable crosslinked polythioester networks, including those formed from cyclic polymers, which offer enhanced swelling and elasticity relative to linear analogues. These findings establish a framework for designing low Tc monomers and recyclable network polymers, advancing the development of closed-loop materials for a circular plastics economy.
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2025-05-27
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Dissertation