TUHH Open Research
 

Lignin coating of alginate aerogels

Journal
Progress in organic coatings  
Volume
222
Article Number
110609
Citation
Progress in Organic Coatings 22: 110609 (2026)
Publisher DOI
10.1016/j.porgcoat.2026.110609
Publisher
Elsevier
This study introduces an integrated and scalable strategy for lignin coating of biopolymer aerogels by embedding the coating step directly into the solvent-exchange stage, thereby enabling in situ coating without additional post-processing. This integration represents a fundamental process innovation, converting a mandatory pro¬ cessing step into a scalable route for functionalization. Millimeter-sized alginate aerogel beads, used as a model polysaccharide system, retained their microstructure upon coating. Lignins with different molecular-weight (Mw) fractions were applied as single or multilayer coatings to study layer formation and surface morphology, while coating functionality was evaluated by dynamic vapor sorption (DVS) using two distinct lignin types. Surface properties were analyzed by scanning electron microscopy (SEM), 3D profilometry, and time-of-flight secondary ion mass spectrometry (ToF-SIMS). ToF-SIMS revealed Mw as the key factor controlling penetration: low-Mw lignins diffused deeper, whereas higher-Mw fractions formed compact outer layers. DVS showed that optimized lignin coatings reduced moisture uptake from ~42 wt% for pristine alginate to ~26 wt% at 90% relative humidity. Covalent post-coating cross-linking further improved dimensional stability, limiting shrinkage to 21% at 70% relative humidity. Thus, the present coatings are intended to improve resistance to water-vapor uptake and dimensional collapse under high-humidity conditions rather than to provide liquidwater repellency or waterproofing. Once layer formation is achieved, lignin molecular structure, especially when highly condensed, may become more decisive for barrier performance than Mw alone.
Subjects
Aerogels
Alginate
Lignin
Bio-based coating
ToF-SIMS
Supercritical CO2 drying
DDC Class
540: Chemistry
600: Technology