Computational study on the impact of linkage sequence on the structure and dynamics of lignin

Abstract

Lignin, one of the most abundant biopolymers on Earth, is of great research interest due to its industrial applications including biofuel production and materials science. The structural composition of lignin plays an important role in shaping its properties and functionalities. Notably, lignin exhibits substantial compositional diversity, which varies not only between different plant species but even within the same plant. Currently, it is unclear to what extent this compositional diversity plays on the overall structure and dynamics of lignin. To address this question, this paper reports on the development of two models of lignin containing all guaiacyl (G) subunits with varied linkage sequences and makes use of all-atom molecular dynamics simulations to examine the impact of linkage sequence alone on the lignin’s structure and dynamics. This work demonstrates that the structure of the lignin polymer depends on its linkage sequence at temperatures above and below the glass transition temperature (\(T_\textrm{g}\)), but the polymers exhibit similar structural properties as it is approaching the viscous flow state (480 K). At low temperatures, both of lignin models have a local dynamics confined in a cage, but the size of cages varies depending on structural differences. Interestingly, at temperatures higher than \(T_\textrm{g}\), the different linkage sequence leads to the subtle dynamical difference which diminishes at 480 K.