Journal of Polymer Science Part A: Polymer Chemistry, Vol.35, No.12, 2421-2429, 1997
Preparation and Characterization of Aromatic Polyamides Based on Ether-Sulfone-Dicarboxylic Acids
Two ether-sulfone-dicarboxylic acids, 4,4’-[sulfonylbis(2,6-dimethyl-1,4-phenylene)dioxy]dibenzoic acid (Me-III) and 4,4’-[sulfonylbis(1,4-phenylene)dioxy]dibenzoic acid (III), were prepared by the fluorodisplacement of 4,4’-sulfonylbis(2,6-dimethylphenol) and 4,4’-sulfonyldiphenol with p-fluorobenzonitrile, and subsequent alkaline hydrolysis of intermediate dinitriles. Using triphenyl phosphite (TPP) and pyridine as condensing agents, aromatic polyamides containing ether and sulfone links were prepared by the direct polycondensation of the dicarboxylic acids with various aromatic diamines in the N-methyl-2-pyrrolidone (NMP) solution containing dissolved calcium chloride. The inherent viscosities of the resulting polymers were above 0.4 dL/g and up to 1.01 dL/g. Most of the polyamides were readily soluble in polar solvents such as NMP, N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO), and afforded tough and transparent films by solution-casting. Most of the polymers showed distinct glass transition on their differential scanning calorimetry(DSC) curves, and their glass transition temperatures (T-g) were recorded between 212-272 degrees C. The methyl-substituted polyamides showed slightly higher T(g)s than the corresponding unsubstituted ones. The results of the thermogravimetry analysis (TGA) revealed that all the polyamides showed no significant weight loss before 400 degrees C, and the methyl-substituted polymers showed lower initial decomposition temperatures than the unsubstituted ones.
Keywords:DIRECT POLYCONDENSATION;POLYIMIDES