Structure-Property Relationships in Fluorinated Polyimides

The incorporation of fluorine into polyimide chemical structures affects many properties, and can impart superior performance to different properties simultaneously. Because of the great potential for dramatic advances in performance in many areas, fluorine-containing polyimides have been widely synthesized and studied. 

In the overview of structure-property relationships that follows, it should be borne in mind tliat these comparisons are (wherever possible) for those materials where hydrogen has been replaced with fluorine. Cases in the literature where dramatically different monomer structures are used for the fluorinated and unfluorinated polyimides cannot easily be interpreted for effects of fluorine, although such comparisons are often casually made in the literature anyway. For instance, to ascribe die property differences in PMDA-ODA and 6FDA-0DA to fluorine substitution is of little value toward understanding the effect of fluorine, though this is often die extent to which data are available. 

Dielectric Properfies Fluorine substitution often results in an overall decrease in the dielectric constant. However, it can also have the opposite effect, depending on the symmetry of substitution, frequency of measurement, and temperature 12,26,27,29,31-34,51-60 

Optical Properties Fluorine substitution generally results in a significant decrease in refractive index. It can also reduce optical loss 53,61-64 (see later section). 

Mechanical Behavior Fluorine substitution often, but not always, results in decreases in glass transition temperatures. There are counter 

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