Evolution of Fluorinated Polyimide Properties

Many interesting structures have been synthesized and studied while we will not chronicle this history in depth here, it is useful to point out how the structures have evolved as knowledge of structure-property relationships has grown. 

Some of the earliest work on fluorine-containing polyimides was done by Dine-Hart et al., who measured the thcrrnooxidativc stability of an extensive series of polyimides including several in which fluorine was attached directly to the aromatic ring 2.93,94 gnj critchley ei a/., who studied perfluoroalkylene- 

A new and important generation of fluorine-containing polyimides began with the introduction of dianhydrides incorporating the hexafluoroisopropylidene (6F) chemical moiety. Hexafluoroisopropylidenc-containing polymers were 

Perusal of the property and chemical structure tables will demonstrate the astonishing range of diamines that are paired with the 6F dianhydride. The 6F group in the dianhydride imparts good solubility and nearly precludes significant molecular ordering. For these and other reasons, it is an ideal monomer to be paired with diamines burdened by specialized functional tasks. 

Hougham et al. reported that, on average, the decrease in dielectric constant in a polyimide series that was attributable to the change in fractional free volume that accompanied fluorine substitution was greater than 50% Recently, these authors have further refined these estimates.  

Recently two other trifluoromethyl-containing monomers have been introduced—OBABTF and DABTF— that have been shown to decrease the dielectric constant and moisture absorption. Polyimides made from OBABTF had a lower dielectric constant than materials made from the unfluorinated analogue ODA in every case with PMDA, BPDA, and ODPA 

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