Synthesis and characterization of novel poly(amide-imide)s containing hexafluoroisopropylidene linkage

A series of novel soluble poly(amide-imide)s were prepared from the diimide-dicarboxylic acid, 2,2-bis [N-(4-carboxyphenyl)-phthalimidyl]hexafluoropropane, with various diamines by the direct polycondensation in N-methyl-2-pyrrolidinone containing CaCl2 using triphenyl phosphite and pyridine as condensing agents. All the polymers were obtained in quantitative yields with inherent viscosities of 0.78-1.63 dL g(-1). The polymers were amorphous and readily soluble in aprotic polar solvents such as N-methyl-2-pyrrolidinone, N,N- dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide as well as in less polar solvents such as pyridine and gamma-butyrolactone, and also in tetrahydrofuran. The polymer films had tensile strength of 84-129 MPa, an elongation at break range of 6-22%, and a tensile modulus range of 2.0-2.7 GPa. The glass transition temperatures of the polymers were determined by DSC method and they were in the range of 240-282 degrees C. These polymers were fairly stable up to a temperature around or above 400 degrees C, and lose 10% weight in the range of 450-514 degrees C and 440-506 degrees C in nitrogen and air, respectively. (C) 1999 John Wiley & Sons, Inc.