Polyimides are often found in aeronautic and aerospace applications due to their ability to retain their physical and mechanical properties over a wide range of temperatures and in chemically demanding environments. Cross-linked polyimide aerogels retain these same characteristics with added attributes of very low thermal conductivities (~14 mW/m-K under ambient pressure and 4mW/m-K under vacuum), high specific surface areas (~850 m2/g), low dielectric constant (~ 1.1), low densities (0.005-0.15 g/cm3), and high porosities (&gt;85%). Incorporating fluorine moieties into polymers can lead to dramatic improvements to material properties such as increased solubility in organic solvents, lower dielectric constant, increased hydrophobicity, higher thermal stability, and improved optical transparencies. The characteristic properties of the 3-dimensional structures of the polyimide aerogel, formed through gelation of dianhydrides and diamines in polar aprotic solvents, show a wide range of dependence on polymer concentration, monomeric structure, and crosslink density. The polyimide aerogels in this study were synthesized following formulations derived to vary the length of the repeat unit (n), dianhydride fraction (Pyromellitic dianhydride (PMDA) and 4, 4’-Hexafluoroisopropylidene dipthalic anhydride (6FDA)), and the weight percent of total polymer in solution. Previous studies have shown that the use of PMDA in the polymer backbone results in highly transparent aerogels while 6FDA incorporation enhances flexibility. Herein we examine and report the effect on thermal, mechanical, and optical properties via incorporation of fluorinated monomers into the backbone of polyimide aerogels.

Effect of fluorinated monomer incorporation on backbone of polyimide aerogel matrix

2019 Fall National Meeting

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