Incorporating fluorine moieties into polymers can lead to dramatic improvements to many of the characteristics of the material properties such as increased solubility in organic solvents, lower dielectric constant and water uptake, higher thermal and thermo-oxidative stability, better optical transparencies along with higher gas-permeability and flame resistance as compared to their non-fluorinated counterparts. Polymers such as polyimides are desirable materials for aeronautics and space applications due to their ability to retain their physical and mechanical properties over a wide range of temperatures. Cross-linked polyimide aerogels are three dimensional structures with added attributes such as high porosity, low density, extremely high surface areas, low dielectric constants and low thermal conductivity. A highly translucent polyimide aerogel was prepared by combining stoichiometric amounts of pyromellitic dianhydride (PMDA) and 4, 4’-hexafluoroisopropylidene dipthalic anhydride (6FDA)), and (2,2’-dimethylbenzidine (DMBZ) producing polyimide aerogels with optical properties that include high transmission, high clarity, and low haze. Herein we examine the optical property effect of incorporating fluorinated monomers into the backbone of polyimide aerogels as well as the effect on dielectric constant, surface areas, and thermal stabilities. The formulations used for fabrication consisted of combinations of dianhydride and diamine fractions with and without trifluoromethyl (-CF<sub>3</sub>) substituents. Three variables were used for fabrication: the length of the repeat unit (n), dianhydride and diamine fraction, and the weight percent of polymer. Structure property relationships of the resulting aerogels will be discussed.

Influence of trifluoromethyl substituents on optical properties of polyimide aerogels

255th National Meeting (2018)

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