Date of Award

Spring 3-28-2022

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor

William Gramlich

Second Committee Member

Barbara Cole

Third Committee Member

Carl P. Tripp

Additional Committee Members

Matthew Brichacek

Thomas J. Schwartz

Abstract

Most thermoplastics are made from limited fossil-fuel sources and these plastics have very deleterious impacts on the environment. Finding a renewable source to synthesize new thermoplastic polymers with tunable properties like biodegradability, heat resistance, and moisture resistance are ongoing research interests. Lignocellulosic biomass is a promising renewable feedstock for biobased monomers and polymers production. In this work, functionalized 𝛿-hexalactone (FDHL) monomers are hypothesized to be synthesizable from lignocellulosic sourced hydroxymethyl furfural (HMF) and lignin-derived pendant groups, generating a variety of aliphatic polyesters and potentially overcome current polymer challenges. Achieving a higher glass transition temperature (Tg) is one of the main obstacles for the current bio-based thermoplastics. A successful FDHL monomer synthesis used commercially available methyl cyclopentanone-2-carboxylate as a starting material. Different bulky, lignin derivatives were incorporated as pendant groups (aromatic: phenol, 1-naphthol, and 2-phenyl phenol; alkyl: cyclohexanol) in the monomer to increase the glass transition temperature (Tg) beyond that possible from poly(δ-valerolactone). Different acidic to super basic organocatalysts were screened to polymerize these novel monomers in a controlled manner. The polymerizations were carried out at room temperature via ring-opening polymerization technique using benzyl alcohol (BnOH) as an initiator. Different aliphatic polyester polymers with higher molecular weight and low dispersity were synthesized in a controlled manner. Typical equilibrium polymerization behavior was observed at room temperature due to the low ring strain of monomers, and the reaction was observed to be pseudo-first-order to monomer concentration in solution. By adding one phenyl group at the δ-position we found the Tg about +6 °C, and additional phenyl groups at the δ-position yielded the Tg about 39.5 °C which is a 105 °C increase from the unsubstituted poly(δ-valerolactone).

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