NEW POLYMER SYNTHESES .67. KEVLAR-TYPE POLYARAMIDES OF MONOSUBSTITUTED TEREPHTHALIC ACIDS

Polyaramides were prepared from 1,4-diaminobenzene and terephthalic acids with aromatic substituents of various lengths. Using phenoxyterephthalic acid as starting material, the synthetic approach was varied and the polycondensation of silylated 1,4-diaminobenzene with terephthaloyl chlorides was found to be the most satisfactory one. In addition to homopolyamides several copolyamides were prepared. Furthermore, the molecular weight and the end groups were varied. The polyaramides were characterized by elemental analyses, inherent viscosities, WAXS and DSC measurements, IR and NMR spectroscopies, optical microscopy, and thermogravimetric analyses. Despite relatively long substituents, meltable polyaramides were never obtained. However, two homo- and two copolyamides showed a good solubility in pure N-methylpyrrolidone and compatibility with poly(vinylpyrrolidone). Up to concentrations of 20 wt % in concentrated H2SO4, lyotropic solutions were not found.