Synthesis and characterization of halogen-containing polyisophthalamides

Two series of aromatic polyamides were prepared from m-phenylenediamine (MPD) and 4,4′-diaminodiphenyl sulfone (DDS) in combination with a set of new halogenated diacyl chlorides, namely, 5-fluoroisophthaloyl chloride, 5-chloroisophthaloyl chloride, 5-bromoisophthaloyl chloride and 5-iodoisophthaloyl chloride. The polymers were synthesized in high yields and in high molecular weight (as determined by gel permeation chromatography) by means of the low temperature condensation method. Noticeable changes in the spectral characteristics of the halogen-modified polyisophthalamides were observed compared to those of the corresponding unmodified polyisophthalamides. Slight improvements were observed for the glass transition temperatures, which increased 5–30°C relative to those of the conventional polyisophthalamides. Moreover, a correlation was found between the size of the halogen substituents and the increase in T_g values. Thermogravimetric analysis showed that the new polymers are almost as thermally resistant as the unmodified ones, while solubility in organic solvents was some-what poorer.