Main chain modification of aromatic polyamides by incorporation of kinked, flexible monomers

Multiring diamines and diacids containing ether and isopropylidene or hexafluoroisopropylidene bridges between phenyl groups were used alone or together with 1,4‐phenylenediamine and terephthalic acid to prepare flexible or semirigid aromatic polyamides by direct polycondensation using triphenyl phosphite and pyridine as condensing agents. All the polyamides are readily soluble in N,N‐dimethylacetamide, N‐methyl‐2‐pyrrolidone and N,N‐dimethylformamide. The wholly flexible polyamides are completely amorphous whereas those prepared from 1,4‐phenylenediamine or terephthalic acid are partially crystalline and melt in the temperature range from 276 to 330°C. Thermal analysis shows Tg's in the range from 204 to 216°C for the wholly flexible polyamides and in the range from 239 to 257°C for the semirigid ones. Both classes of aromatic polyamides show excellent thermal resistance which is comparable with that of rigid‐rod aramides.