In-Situ Rheological Studies of Cationic Lignin Polymerization in an Acidic Aqueous System

Abstract

The chemistry of lignin polymerization was studied in the past. Insights into the rheological behavior of the lignin polymerization system would provide crucial information required for tailoring lignin polymers with desired properties. The in-situ rheological attributes of lignin polymerization with a cationic monomer, [2-(methacryloyloxy)ethyl] trimethylammonium chloride (METAC), were studied in detail in this work. The influences of process conditions, e.g., temperature, component concentrations, and shear rates, on the viscosity variations of the reaction systems during the polymerization were studied in detail. Temperature, METAC/lignin molar ratio, and shear rate increases led to the enhanced viscosity of the reaction medium and lignin polymer with a higher degree of polymerization. The extended reaction time enhanced the viscosity attributing to the larger molecular weight of the lignin polymer. Additionally, the size of particles in the reaction system dropped as reaction time was extended. The lignin polymer with a larger molecular weight and Rg behaved mainly as a viscose (tan δ > 1 or G″ > G′) material, while the lignin polymer generated with smaller molecular weight and shorter Rg demonstrated strong elastic characteristics with a tan (δ) lower than unity over the frequency range of 0.1−10 rad/s.

Improving Properties of Starch-Based Adhesives with Carboxylic Acids and Enzymatically Polymerized Lignosulfonates

“…MtL8 was used to polymerize a 20% solid content LS solution, while monitoring the changes in molecular weights (MW) and viscosities. As previously reported, the viscosity of lignin increases while it is being polymerized [ 23 , 27 , 36 ]. Polymerization of LS, with a phenolic content of 247.01 mmol/mL, using the laccase led to an increase in MW from an initial average of 53.74 kDa to 750 kDa in 90 min.…”