Organo-Soluble Fluorinated Polyimides Derived from Bis-Trifluoromethyl-Substituted Aromatic Diamines and Various Aromatic Dianhydrides

A new diamine monomer with bis-trifluoromethyl-substituted phenyl in the side chain, α,α-bis (4-amino-3,5-dimethylphenyl)-3′,5′-bis(trifluoromethyl)phenyl methane (6FMA) was successfully synthesized. A series of fluorinated polyimides (PI-IIa-d) were prepared by reacting the diamine with various aromatic dianhydrides. For comparison, another series of polyimides (PI-Ia-d) derived from another diamine with single-trifluoromethyl-substituted phenyl in the side chain, α,α-bis(4-amino-3,5-dimethylphenyl)-3′-trifluoromethyl phenyl methane and the same dianhydrides were also synthesized. The polymers were characterized by inherent viscosity, elemental analysis, Fourier transform-infrared, X-ray, ultraviolet-visible analysis, moisture absorption, thermogravimetric analysis, and differential scanning calorimetry measurements. It was shown that PI-II polyimides exhibited good film formability, enhanced solubility, good thermal stability, superior optical transparency, and acceptable mechanical properties. In addition, the polyimides derived from 3,3′,4,4′-benzophenone tetracarboxylic dianhydride and 6FMA showed high sensitivity to i-line (365 nm) of a high-pressure mercury lamp. The combined properties of the polyimides make them good candidates for microelectronic fabrications.