Lignins isolated from woody biomass have drawn much attention as an aromatic natural polymer, and the researches on their applications are markedly being advanced. Molecular structure and size of isolated lignins have not been clear yet, although such lignin characters are very important for lignin utilization. In this study, we attempted to measure absolute molar masses of technical lignins (hardwood and softwood kraft lignins; HKL and SKL, respectively) and polymeric lignin models that were comprised only of 8-O-4’ interunitary linkage with a size-exclusion chromatograph equipped with a multi-angle laser light scattering detector (SEC-MALLS).<br/>The SEC-MALLS measurement gave us interesting information on molar mass as compared to conventional SEC measurement with a calibration curve of polystyrene standards. Weight-average molar masses (Mw) of HKL and SKL obtained by the MALLS detector were about 5 times larger than those obtained from the conventional SEC method. By contrast, Mw of polymeric lignin models obtained by MALLS were almost comparable to those obtained from the conventional method. This difference in Mn between the technical lignins and the polymeric models implied that technical lignins had denser and more compact structure than the models at the same hydrodynamic radius in the measurement solvent. The dense structure must be attributed to branched structure, because the polymeric lignin models did not have branched structure. Thus, we elucidated molecular size of technical lignins, and predicted molecular structure through SEC-MALLS measurements.<br/>

Comparison of molar mass between technical lignins and <i>8-O-4' </i>type of polymeric lignin models

2019 Spring National Meeting

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Comparison of molar mass between technical lignins and 8-O-4' type of polymeric lignin models