The present work focuses on modifying a non-steroid anti-inflammatory drug (NSAID) into an ionic liquid and evaluating the resulting thermal behavior and structural changes of the drug. Naproxen was chosen as the NSAID molecule due to thermal stability and limited examples of its use as an ionic liquid in current literature. Lidocaine was chosen as the counterion based on a screening study of potential ionic liquid formers. The screening included both potential protic and aprotic formation and counterions were included with consideration to pKa, hydrogen bonding ability, molecular size, diffuse charge distribution and functional groups. Analytical techniques used to evaluate the counterions included high performance liquid chromatography (HPLC), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Naproxen and lidocaine were then combined in varying molar ratios to determine the thermal behavior of the mixtures. The samples with equimolar, or higher, ratio of naproxen showed a phase which had a melting point of 82–85 °C. The DSC data was analyzed using a modified Tamman plot, resulting in the unexpected and previously unreported behavior of ionic liquid formation at a 2:1 molar ratio of naproxen to lidocaine, referred to as IL1 in this research. This stoichiometry was confirmed through Fourier Transformed Infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy methods. The samples that contained a higher molar ratio of lidocaine than naproxen, resulted in material more consistent with higher-order complex clusters. Further characterization of IL1 found that the material demonstrated behaviors of an ionic liquid, including weak intermolecular forces and at least partial ionization of the drug and counterion.
|Advisor:||Gupta, Pardeep K.|
|Commitee:||Wigent, Rod, Jonnalagadda, Sriramakamal, Dalwadi, Gautam, McQueen, Lisa|
|School:||University of the Sciences in Philadelphia|
|School Location:||United States -- Pennsylvania|
|Source:||DAI-B 81/4(E), Dissertation Abstracts International|
|Keywords:||Ionic liquid formation, Non-steroid anti-inflammatory drug|
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