Synthesis and characterization of new inherent photoimageable polyimides based on fluorinated tetramethyl-substituted diphenylmethanediamines

A novel fluorinated tetramethyl-substituted diphenylmethanediamine, α,α-bis(4-amino-3,5-dimethylphenyl)-3′-trifluoromethylphenylmethane (TFPM) was synthesized via a straightforward two-step procedure with high yield, which was then employed to react with 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) to afford soluble and inherent photoimageable polyimide BTDA–TFPM [PI(BTDA–TFPM)]. Experimental results indicated that PI(BTDA–TFPM) possesses good combined chemical and physical properties, of which thermal stability with initial thermal decomposition temperature of 526 °C and glass transition temperature of 298 °C. The polyimide has excellent solubility both in strong bipolar solvents, such as NMP and DMAc, and in common organic solvents, such as THF and dioxane, etc. Strong and flexible polymer coatings or films could be prepared by just casting the polymer solution on glass substrate, followed by thermal baking at a temperature lower than 200 °C. The novel polyimide has good electric insulating properties and low dielectric constant and dissipation factor. Fine photopattern could be processed by directly exposing the polyimide coating upon UV i-line, followed by developing with an organic solution developer.