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A number of mixed aromatic/cycloaliphatic as well as fully nonaromatic polyimides have been prepared. Whereas all the poly(amic acids) derived from nonaromatic diamines involved salt-formation during the initial stages of the polymerization, the majority of these eventually formed homogeneous, highly viscous polymer solutions. Only in a few select cases involving all nonaromatic monomers traditional solution polymerization was unsuccessful. The polyimide derived from hexafluoroisopropylidene diphthalic anhydride (6FDA) and trans- 1,4-diaminocyclohexane (DACH) yielded films with tough mechanical properties, a glass transition temperature of ∼360°C, good solvent resistance, and a low dielectric constant of 2.6. Thermal stability of this polyimide as determined by thermal gravimetric analysis in both air and nitrogen was quite good, exhibiting a weight loss of only 0.07 wt%/h at 350°C under isothermal …