Researcher ORCID Identifier

0009-0009-6971-4304

Graduation Year

2025

Document Type

Open Access Senior Thesis

Degree Name

Bachelor of Arts

Department

Chemistry

Reader 1

Dan O'Leary

Reader 2

Rebecca Dipucchio

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© 2025 Charise D Young

Abstract

Polyurethanes are widely used polymers synthesized from diisocyanate and diol molecules. They are ubiquitous polymeric materials with important industrial applications. Their increasing market value prompts the need for selective and efficient production which can be achieved through N-Heterocyclic carbene (NHC) catalysis. N-heterocyclic carbenes are heterocyclic molecules containing a carbene atom and at least one nitrogen adjacent to the carbene center. The nitrogen substituents on the adjacent nitrogen play an important role in influencing their steric and electronic properties and resultant reactivity.1,2 There is a lack of a comprehensive understanding of the steric and electronic properties of NHCs and how these affect polyurethane reactions. This thesis seeks to fill the gap in understanding how the interplay of steric and electronic modifications to N-substitutions affects NHC catalysis for polyurethane synthesis.

First, I propose to synthesize 16 target NHCs with different steric and electronic properties, specifically examining factors such as alkyl chain length, steric hindrance, and variations in electron-donating or electron-withdrawing groups. Structural analysis of the NHCs will be carried out via Fourier Transforrm Infrared (FTIR), 1H Nuclear Magnetic Resonance (NMR), and 13C NMR. I will then perform steric analysis of the NHCs using buried volume calculations, evaluate electronic effects through Tolman’s Electronic Parameter (TEP), and assess basicity by analyzing the acidity of the protonated NHC species using DFT calculations. The polyurethane products will be analyzed by 1H NMR and Size Exclusion Chromatography (SEC). Parameters such as the number average molecular weight (Mn), weight average molecular weight (Mw), conversion, dispersity (D), degree of polymerization will be determined. Thermal analysis of the polyurethanes will also be carried out using Differential Scanning Calorimetry (DSC) and Thermogravimetric analysis (TGA). These data will allow for a comparative analysis of how NHC structure influences polymerization behavior and catalytic efficiency.

Overall, this research will investigate functionalized catalysis for applications in polyurethane synthesis by examining the effects of NHCs with varying electronic and steric properties.

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