Lignin-based Thermosets: From Structure-Reactivity Relationships to Degradable Material Design
Time: Thu 2026-09-17 10.00
Location: F3, Lindstedtvägen 26
Language: English
Subject area: Fibre and Polymer Science
Doctoral student: Fika Andriani , Träkemi och massateknologi
Opponent: Professor Orlando Rojas, The University of British Columbia, Canada
Supervisor: Professor Martin Lawoko, Träkemi och massateknologi, Wallenberg Wood Science Center, Wallenberg Wood Science Center; Professor Mats Johansson, Ytbehandlingsteknik, Wallenberg Wood Science Center, Wallenberg Wood Science Center, KTH
QC 20260821
Abstract
Carboxymethylation and oxidative carboxylation of four available lignins were investigated as routes to introduce carboxylic acid functionality for crosslinking with epoxidized linseed oil. Hardwood lignins showed consistently higher reactivity toward both routes, explained with DFT calculations and conformational modeling linking the molecular conformation of syringyl-rich lignin to greater hydroxy group accessibility. WAXS analysis showed that oxidative carboxylation disrupted supramolecular packing more extensively than carboxymethylation, correlating with the complete solubility of oxidized lignins and homogeneous mixing with the epoxide matrix.
A feasibility study confirmed crosslinked network formation but revealed phase separation and brittleness as key limitations. Incorporating oxidized lignin with PEG-400 yielded thermosets with approximately 90% bio-based content, gel contents of 88–90%, glass transition temperatures of 93–109 °C, and hydrophobic surfaces. Both thermosets degraded completely within 48 hours under alkaline conditions, while remaining stable under near-physiological conditions for 14 days, consistent with a surface-initiated erosion mechanism.
These findings establish a structure-property framework linking lignin molecular architecture to modification efficiency, thermoset performance, and controlled end-of-life degradation.