The Air Force has recently gained interest in using polyimines to synthesize Covalent Organic Frameworks (COFs) for electronic applications. However, COFs are difficult to process into the thin films and membranes that are needed for electronic devices due to their low solubility. 4MMCA-PDA is a novel linear polyimine with great solubility in common organic solvents that is currently being studied as part of a new method of COF synthesis. Our study investigates the synthesis of 4MMCA-PDA and ways to control the molecular weight (MW) of the polymer. High MW makes polymers stronger and stretchier while low MW polymers are more soluble and more brittle. Three aspects of the step-growth polycondensation (reaction time, temperature, and concentration) were adjusted to determine their effect on the MW of the product. Analysis was performed using 1H NMR, FT-IR, and Gel Permeation Chromatography (GPC). Overall, we found that MW remains constant around 20 kDa after heating the reaction mixture up to 4 hours, but increases after the mixture is left at room temperature for an additional 48 hours. Furthermore, MW increased slightly from 40 kDa to 59 kDa as temperature increased. Finally, MW increased from 20 kDa to 59 kDa as concentration was increased 0.064M, but remained constant around 55-60 kDa even as concentration was increased to 0.128M. Therefore, we conclude that low concentration and short reaction time will result in low MW polyimines while higher concentration and longer reaction time will result in high MW polyimines. This knowledge may be used to increase polymer solubility and aid in the efforts to process COFs into films and membranes.
Author(s): Morgan Loveday, Student Researcher UES Biological and Nanoscale Technologies Division
Advisor(s): Dr. Ly Tran, Dr. Nicholas Glavin
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