Synthesis and Characterization of New Organosoluble Polyamides and Polyimides Based on 2,2-Bis[4- (4-aminophenoxy)-3,5-dimethylphenyl]- hexafluoropropane

A new hexafluoro-containing diamine monomer, 2,2-bis[4-(4-aminophenoxy)-3,5-dimethylphenyl]-bexafluoropropane (TBAPHP), was synthesized in three steps, starting from hexafluoroacetone sesquihydrate and 2,6-xylenol. The monomer was reacted with various aromatic dicarboxylic acids and tetracarboxylic dianhydrides to produce a series of polyamides and polyimides, respectively. The polyamides were prepared under Yamazaki reaction conditions. The polyimides were prepared by a two-stage procedure that included a ring-opening polyaddition yielding poly(amic acid)s, followed by a cyclodehydration to polyimides. The obtained polymers had inherent viscosities of 0.52-0.82 dL.g -1 . All of the polymers dissolved in polar solvents, such as N-methyl-2-pyrrolidinone, N,N-dimethylacetamide, and N,N-dimethyl-formamide. The polyimides derived from 4,4'-oxydiphthalic anhydride and 3,3',4,4'-benzophenonetetracarboxylic dianhydride exhibited an excellent solubility and were dissolved in cyclohexanone, pyridine, tetrahydrofuran, and chloroform. These polymers showed glass transition temperatures of 231-301 °C and decomposition temperatures at 10% weight loss ranging from 470 to 495 °C in nitrogen and from 473 to 505 °C in air. The tough and flexible polymer films obtained from solution casting showed tensile strengths of 78-96 MPa and tensile moduli of 2,0-2,4 GPa. Polymers containing methyl substituents had higher solubilities and T g values than those without methyl substituents. In addition, the bexafluoroisopropylidene containing polymers exhibited a higher solubility and thermal stability than those containing isopropylidene units. UV-visible absorption spectra revealed that the polyimides showed a better transparency than the polyamides.