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

The molecular mass distribution of naphthalenesulfonate condensation p roducts (PNS) was investigated using ion-pair reversed-phase chromatog raphy and ultrafiltration. The chromatograms obtained under an optimiz ed solvent elution program yielded nearly 20 well resolved peaks corre sponding to low and intermediate molecular mass species. A distinct br oad peak was also resolved and attributed to polymeric species with re lative molecular mass in excess of 5000. Under isocratic elution condi tions, 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 mol ecular mass species; the latter also exhibited a broad distribution of molecular mass. Significant differences were also found amongst diffe rent commercial PNS products with similar average chemical composition .