The synthesis and solution properties of some rigid‐chain, water‐soluble polymers: Poly[N,N′‐(sulfo‐phenylene)phthalamide]s and poly[N,N′‐(sulfo‐p‐phenylene)pyromellitimide]

Abstract Poly[ N , N ′‐(sulfo‐phenylene)phthalamid]es and poly[ N , N ′‐(sulfo‐ p ‐phenylene)pyromellitimide] were prepared in water‐soluble form and were found to have unique solution properties, similar in some respects to xanthan. The polymer most investigated, poly[ N , N ′‐(sulfo‐ p ‐phenylene)terephthalamide] (PPT‐S), is produced as the dimethylacetamide (DMAC) salt by the solution polymerization of 2,5‐diaminobenzenesulfonic acid with terephthaloyl chloride in DMAC containing LiCl. The isolated polymer requires heating in water to dissolve; the resulting cooled solutions are viscous or gels at concentrations as low as 0.4%. They are highly birefringent, exhibit circular dichroism properties, and are viscosity‐sensitive to salt. Solutions of this polymer mixed with those of guar or hydroxyethyl cellulose give significantly enhanced viscosity. The polymer is relatively low molecular weight, ca. 5000 estimated from viscosity data. Some meta and para isomeric analogs of PPT‐S were prepared; these polymers have similar properties except they are more soluble in water, and higher concentrations are required to obtain significant viscosity. Poly[ N , N ′‐(sulfo‐ p ‐phenylene) pyromellitimide] (PIM‐S) was prepared similarly from 2,5‐diaminobenzenesulfonic acid and pyromellitic dianhydride. Its aqueous solution properties are similar to those of PPT‐S. It appears that these relatively low‐molecular‐weight rigid‐chain polymers associate in water to form a network that results in viscous solutions at low concentrations.