(519h) Resolving the Discrepancies in the True Molecular Weight of Lignins with the Assistance of the ALPHA Process

Lignin constitutes nearly 30% of all renewable carbons in the biosphere and hold tremendous potential value as a source material for a wide breadth of downstream applications. However, the complexity and heterogeneity of lignin streams, as a result of the delignification process and natural variety in source materials, make it exceptionally difficult to develop. Advancement of lignin technologies hinges on the ability to clean and purify technical lignins into well-defined and fractionated streams. Here we employ a patented process titled “Aqueous Lignin Purification with Hot Agents” (ALPHA). The characterization of complex polymers is a bottleneck for sustainable material development, with lignin being no exception. Currently, there are enormous discrepancies in literature regarding the true molecular weights of lignin and presents a notable obstacle for improving purification, fractionation, and material models. One promising technique for calculating the absolute molecular weight and distribution of lignins is size-exclusion chromatography (SEC) coupled with multi-angle light scattering equipped with an infrared laser (MALS_IR) and bandwidth filters. This approach both suppresses and blocks fluorescence, respectively, which has led to overestimation of molecular weight of previous MALS experiments. We demonstrate how SEC-MALS_IR can be used to accurately calculate the molecular weight distributions of a variety of lignin sources and ALPHA-processed fractions. A universal-calibration style technique is applied to compensate for lingering non-SEC interactions, fluorescent, and absorption related phenomena that cause erroneous and poorly reproducible measurements. In doing so, we decouple discrepancies discovered between mobile phases, lignin fractions and the individual contributions of non-ideal behavior during liquid chromatography and light scattering. Moving forward, this work presents an improved methodology of using a SEC-MAL_IR technique to help bridge the characterization gap that inhibits meaningful lignin development across the field.