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The characteristics of structural and properties of four sodium lignosulfonate (LS) fractions with narrow molecular weight (Mw) distribution isolated by gel column chromatography were investigated with infrared spectroscopy, elemental analysis, 13C NMR analysis, fluorescence spectroscopy and thermogravimetric analysis. LS with higher Mw possesses more aryl ring structural units and the side-chain of the structural unit is mostly composed of propanol rather than propane. With the increase of Mw of LS, the contents of sulfonic group and methoxy group decrease. The critical aggregation concentration (CAC) of LS aqueous solution was determined by fluorescence spectroscopy, which shows that the CAC of LS with higher Mw is lower, indicating that the LS molecule with low Mw is easier to aggregate. TGA results indicate that the weight loss of LS tends to be slow and the thermal stability enhances with the increase in Mw. The dispersive effect of LS with different Mw to dimethomorph suspension shows that the sediment layer thickness and index of dispersity and stability both decease with increasing Mw of LS, which indicates that LS with higher Mw has a better dispersion performance.
Li et al. (Sun,) studied this question.