Fluorine substituted aromatic polyamides have been prepared by polycondensation of fluorinated m-phenylenediamines and isophthaloyl chlorides in dimethyl acetamide. In this experiment, 5-fluoro-, 2, 4- and 4, 6-difluoro- and non-substituted 1, 3-phenylenediamines as amine component, and 5-fluoro-, 4, 6-difluoro- and non-substituted isophthalic acids as acid component were used. The thermostability of these fluorine substituted aromatic polymers was evaluated by the thermogravimetric and the differential thermal analysis, and the results were compared with those of the fluorine-free poly(1, 3-phenylene-isophthalamide). It was found that the polyamides substituted ortho- or/and pa.ra-positions especially 4, 6-position on 1, 3-phenylenediamino group with fluorine increased the thermostability considerably. On the contrary, the polyamides containing 4, 6-difluoroisophthaloyi group. decreased the thermosta-bility. On the other hand, almost no effect on thermostability was found from the polyamide having a fluorine atom at the meta-position to amido or carbonyl groups on either phenylene-diamino- or isophthaloyl-group.
Further, two other kinds of fluorine-containing polyamides prepared from 2, 5-difluoro-1, 4- phenylenediamine and terephthalic acid, or 2, 2'-difluoro-4, 4'-diaminodiphenyl ether and terephthalic acid have been studied. It was found the former polyamide in which fluorine occupied the ortho-positions to NH brought a favorable thermostability, but in the latter in which fluorines substituted meta positions to NH, had no influence on the thermostability.