| Abstract: | Methyl-substituted or unsubstituted aromatic dicarboxylic acids and diamines containing ether and sulfone linkages between phenylene units were used alone or in combination with p-phenylenediamine, m-phenylenediamine, terephthalic acid, and isophthalic acid to prepare flexible or semirigid aromatic polyamides by direct polycondensation activated by triphenyl phosphite and pyridine. The inherent viscosities of the obtained polymers ranged from 0.40 to 1.01 dL/g. The wholly flexible polyamides are amorphous, are readily soluble in N,N-dimethylacetamide, dimethyl sulfoxide, and m-cresol, and can afford transparent, flexible, and tough films by solution-casting. The polyamides prepared from p-phenylenediamine or terephthalic acid are partially crystalline and melt around 410°C. Differential scanning calorimetry shows glass transition temperature in the 202–255°C range for the wholly flexible polyamides. All the polyamides are thermally stable in excess of 400°C. The methyl-substituted polyamides had higher glass transition temperatures, but lower initial decomposition temperatures, than the corresponding unsubstituted polyamides. |
