Synthesis and characterization of new soluble polyamides containing phthalimide pendent group

A dicarboxylic acid monomer, 5-phthalimidoisophthalic acid, containing a ph thalimide pendent group was prepared by the condensation of 6-aminoisophtha lic acid and phthalic anhydride in glacial acetic anhydride. The monomer wa s reacted with various aromatic diamines to produce polyamides using triphe nyl phosphite and pyridine as condensing agents. These polyamides were prod uced with inherent viscosities of 0.64-1.14 dL g(-1). All the polymers, cha racterized by wide-angle X-ray diffraction, revealed an amorphous nature re sulting from the presence of the bulky pendent group. These polyamides exhi bited excellent solubility in a variety of solvents such as N-methyl-2-pyrr olidinone, N,N-dimethylacetamide (DMAc), N,N-dimethylformamide, dimethyl su lfoxide, pyridine, and cyclohexanone. These polyamides showed glass-transit ion temperatures (T-g's) between 247 and 273 degreesC (by DSC) and 248 and 337 degreesC (by a dynamic mechanical analyzer). The thermogravimetric anal ytic measurement revealed the decomposition temperature at 10% weight-loss temperatures (Td(10)) ranging from 442 to 530 degreesC in nitrogen. The pol yamides containing phthalimide groups exhibited higher T-g and Td(10) value s than those having no phthalimide groups. Transparent, tough, and flexible films of these polyamides could be cast from the DMAc solutions. These cas ting films had tensile strengths ranging from 81 to 126 MPa, elongations at break ranging from 7 to 13%, and tensile moduli ranging from 2.0 to 2.9 GP a. (C) 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1557-1563 , 2001