Synthesis, characterization, and properties of semifluorinated organo-soluble new aromatic polyamides

A series of organo-soluble new polyamides were synthesized by the direct polycondensation of different semifluorinated aromatic diamines, namely 4,4-bis[3'-trifluoromethyl-4'(4-amino benzoxy)benzyl]biphenyl; 4,4-bis(aminophenoxy)-3'3-trifluoromethyl terphenyl; 1,3-bis[3'-trifluoromethyl-4'(4-amino benzoxy)benzyl]benzene; 2,6-bis(3'-trifluoromethyl-p-aminobiphenyl ether)pyridine; and 2,5-bis(3'-trifluoromethyl-p-aminobiphenyl ether)thiophene with 5-t-butyl-isophthalic acid. The polymers were fully characterized by elemental analysis and IR, NMR spectroscopies. The synthesized polyamides were soluble in several organic solvents such as 1-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, and dimethyl sulfoxide at room temperature. They showed inherent viscosities of 0.420.63 dl/g. The polyamides exhibited weight-average molecular weights of up to 233,000, which depended on the exact repeating unit structure. The polyamides synthesized from 4,4-bis[3'-trifluoromethyl-4'(4-amino benzoxy)benzyl]biphenyl and 5-t-butyl isophthalic acid exhibited highest glass-transition temperatures 261 degrees C (evaluated by differential scanning calorimetry) in nitrogen. These polyamides showed good thermal stability up to 475 degrees C for a 10% weight loss in air. The polyamides films were clear and flexible in nature with tensile strengths of up to 88MPa, modulus of elasticity of up to 1.81GPa, and elongations at break of up to 25%, which depended on the exact repeating unit structure. X-ray diffraction measurements indicated that these polyamides were amorphous in nature. Copyright (C) 2010 John Wiley & Sons, Ltd.