Novel ortho-linked and CF3-substituted poly(amide-imide)s: Optical and thermal behavior

A new ortho-linked dicarboxylic acid monomer, 1,5-bis(4-trifluoromethyl-2-trimellitimidophenoxy)naphthalene (BFTPN), bearing two preformed imide rings, two trifluoromethyl groups, and two ether linkages was synthesized by the condensation reaction between 1,5-bis(2-amino-4-trifluoromethylphenoxy)naphthalene (BAFPN) and trimellitic anhydride in refluxing glacial acetic acid. Monomer BFTPN was then utilized to prepare a series of novel trifluoromethyl-containing poly(amide-imide)s via a direct phosphorylation polycondensation with various aromatic diamines. Weight and number-average molecular weights (M¯w and M¯n) of the resulting polymers were determined using gel-permeation chromatography (GPC). The polymeric samples were readily soluble in a variety of organic solvents and formed low-colored and flexible thin films via solution casting. The values of absorption edge wavelength (λ0) were determined by UV-vis spectroscopy, and all of the resulting poly(amide-imide)s films exhibited high optical transparency. From differential scanning calorimetry (DSC) thermograms, the polymers showed glass-transition temperatures between 305 and 323 °C. Thermal behaviors of the obtained polymers were characterized by thermogravimetric analysis (TGA), and the 10% weight loss temperatures of the poly(ester-ether-imide)s were found to be in excess of 520 °C in nitrogen.