Fluoro-containing poly(amide-imide)s with sterically hindered pendants: Synthesis and characterization

A structurally kinked fluorinated diacid, 2,6-bis(N-trimellitimido)-4-trifluoromethyl-4′-phenoxydiphenyl ether (TFPDPE) was synthesized and then used for preparing a new class of fluoro-containing poly(amide-imide)s via phosphorylation polyamidation with four diamines including 4,4′-(oxidianiline, 2,6-diamino-4-trifluoromethyl)-4′-phenoxydiphenyl ether, 1,5-bis(2-amino4-trifluoromethylphenoxy)naphthalene, and 2,2′-bis(2-amino-4-trifluoromethylphenoxy)-1,1′-binaphthyl. Chemical structure of monomer TFPDPE as well as the resulted polymers was fully confirmed by IR and NMR spectroscopy. Limited viscosity numbers ([η]’s) of the resulting polymers at 25 °C were measured. The values of M ¯ w and M ¯ n were determined using gel-permeation chromatography (GPC). In addition, the absorption edge values (λ0) obtained from their UV curves were determined, and all the resulting poly(amide-imide)s exhibited high optical transparency. The crystallinity of the polymers was estimated by wide-angle X-ray diffraction (WXRD), and the resulted polymers exhibited nearly an amorphous nature. To study on the surface morphologies, the scanning electron microscopy (SEM) images of the poly(amide-imide)s were taken. Furthermore, solubility of the samples in various kinds of organic solvents was tested. From differential scanning calorimetric (DSC) analyses, the polymers showed Tgʹs between 304 and 328 °C. Thermo-stability of the polymers was determined by thermogravimetric analysis (TGA), and the 10% weight loss temperatures of the poly(amide-imide)s were found to be in the range of 548–553 °C.