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 prepar e 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-py rrolidone and N,N-dimethylformamide. The wholly flexible polyamides ar e completely amorphous whereas those prepared from 1,4-phenylenediamin e or terephthalic acid are partially crystalline and melt in the tempe rature range from 276 to 330 degrees C. Thermal analysis shows T-g's i n the range from 204 to 216 degrees C for the wholly flexible polyamid es and in the range from 239 to 257 degrees C for the semirigid ones. Both classes of aromatic polyamides show excellent thermal resistance which is comparable with that of rigid-rod aramides.