Synthesis and properties of aliphatic‐aromatic poly(amide‐imide)s from sulfonyldianilines and N,N′‐bis(ω‐carboxyalkyl)pyromellitimides

Seven imide‐containing dicarboxylic acids IIa‐g were synthesized from pyromellitic dianhydride and amino acids of the formula HOOC—(CH₂)_m—NH₂, with m—1,2,3,4,5,10,11. These diacids were condensed directly with 3,3′‐ or 4,4′‐sulfonyldianiline using triphenyl phosphite in N‐methyl‐2‐pyrrolidone (NMP)‐pyridine solution containing calcium chloride and lithium chloride. The resulting poly(amide‐imide)s have moderate to high inherent viscosities ranging from 0.47 to 2.02 dL/g in dimethylacetamide. These polymers showed excellent solubility in polar solvents such as NMP, and most of them could be cast into transparent and tough films. Glass transition temperatures (T_gs) of these poly(amide‐imide)s were recorded in the range 116–258°C and increased with decreasing number of methylene groups in the repeated unit. The polymers with longer aliphatic chains (e.g., m = 10 and 11) exhibited higher crystallinity, higher initial decomposition temperature, and lower solubility in polar solvents.