*3.8. Molecular Weights of Lignins*

The SEC analysis on the lignin samples (Figure 6) was used to evaluate its molecular size distribution. Table 4 shows the most important parameters calculated from the chromatograms. Compared with MWL, the molar mass distribution of PFL showed a lower M<sup>n</sup> but a higher Mw. In order to explain this, in PFL a larger number of small and big molecules should be present in relation to MWL; that is, a much higher polydispersity than that of MWL. In fact, it is almost five times higher (2.5 vs. 12.4), according to the SEC data. This points out that there was a concurrent depolymerization and recondensation of lignin in the reaction medium. Taking as reference the simple C9 formulas (Table 4) to calculate the molecular mass of each C9 unit and the value of M<sup>w</sup> as an average representative of the lignin molecular size, values of 116.5 and 246.2 units C9/lignin molecule for MWL and PFL, respectively, were calculated.

**Figure 6.** SEC chromatograms of MWL and PFL (the molecular weight is estimated relative to polystyrene standards).
