New organosoluble polyimides with low dielectric constants derived from bis[4-(2-trifluoromethyl-4-aminophenoxy)phenyl] diphenylmethylene

A new kink diamine with trifluoromethyl group on either side, bis[4‐(2‐trifluoromethyl‐4‐aminophenoxy)phenyl]diphenylmethane(BTFAPDM), was reacted with various aromatic dianhydrides to prepare polyimides via poly (amic acid) precursors followed by thermal or chemical imidization. Polyimides were prepared using 3,3′, 4,4′‐biphenyltetracarboxylic dianhydride(1), 4,4′‐oxydiphthalic anhydride(2), 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (3), 4,4′‐sulfonyldiphthalic anhydride(4), and 4,4′‐hexafluoroisopropylidene‐diphathalic anhydride(5). The fluoro‐polyimides exhibited low dielectric constants between 2.46 and 2.98, light color, and excellent high solubility. They exhibited glass transition temperatures between 227 and 253°C, and possessed a coefficient of thermal expansion (CTE) of 60‐88 ppm/°C. Polymers PI‐2, PI‐3, PI‐4, PI‐5 showed excellent solubility in the organic solvents: N‐methyl‐2‐pyrrolidinone (NMP), N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pyridkie and tetrahydrofuran (THF). Inherent viscosity of the polyimides were found to range between 0.58 and 0.72 dLg‐1. Thermogravimetric analysis of the polyimides revealed a high thermal stability decomposition temperature in excess of 500°C in nitrogen. Temperature at 10 % weight loss was found to be in the range 506‐563°C and 498‐557°C in nitrogen and air, respectively. The polyimide films had a tensile strength in the range 75‐87 MPa; tensile modulus, 1.5‐2.2 GPa; and elongation at break, 6‐7%.