CHARACTERIZATION OF POLY(NAPHTHALENESULFONATE) SALTS BY ION-PAIR CHROMATOGRAPHY AND ULTRAFILTRATION

The molecular mass distribution of naphthalenesulfonate condensation products (PNS) was investigated using ion-pair reversed-phase chromatography and ultrafiltration. The chromatograms obtained under an optimized solvent elution program yielded nearly 20 well resolved peaks corresponding to low and intermediate molecular mass species. A distinct broad peak was also resolved and attributed to polymeric species with relative molecular mass in excess of 5000. Under isocratic elution conditions, a linear relationship was obtained between the peak number and the log of the retention time for the first 17 peaks, thus indicating a homologous series of linear oligomers. The fractionation of the PNS mixtures by ultrafiltration enabled further resolution of the high molecular mass species; the latter also exhibited a broad distribution of molecular mass. Significant differences were also found amongst different commercial PNS products with similar average chemical composition.