Lignin-derived precursors were used in the synthesis of bio-based high-performance polymers. The project consisted of synthesizing a series of poly(ester amide)s (PEAs) from lignin building blocks and natural amino acids. In particular, the amino acid moieties were incorporated into the PEAs’ architecture to explore the effect of the side-chain size on the thermal properties and the crystallinity of the resulting materials. The polymers, which were prepared by melt polycondensation, all possessed high thermal stability in nitrogen and air with onsets of thermal degradation (Td onset) exceeding 330 °C and glass transition temperatures (Tg) ranging from 136 °C – 238 °C. It is worth noting that the Tg greatly depended on the size of the pendant R-group on the amino acid. Remarkably, the thermal stability was mostly maintained even after subjecting the polymers to various pH media (pH 1, 4 and 8) for 1 week at 50 °C. Furthermore, wide-angle X-ray scattering experiments revealed semi-crystalline polymers with identical diffraction patterns and percent crystallinity ranging from 21 – 37%. To probe the impact of chirality on the thermal properties, a meso polymer of DL-alanine was prepared and compared to the chiral version. A slight drop in the Td onset and Tg of the DL-alanine-containing polymer relative to the L-alanine counterpart occurred, signifying moderate thermal stability resulting from the chiral group. Overall, these characteristics make these bio-based PEAs potential candidates for further investigation as alternatives to petrochemical-derived thermoplastics for high-performance materials.
| Identifer | oai:union.ndltd.org:MSSTATE/oai:scholarsjunction.msstate.edu:td-5184 |
| Date | 07 August 2020 |
| Creators | Munyaneza, Nuwayo Eric |
| Publisher | Scholars Junction |
| Source Sets | Mississippi State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
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