Full title: Solvent-Resistant Lignin-Epoxy Hybrid Nanoparticles for Covalent Surface Modification and High-Strength Particulate Adhesives
Tao Zou, Mika H. Sipponen, Alexander Henn, and Monika Österberg
Conclusions of the work: In this work, we systematically studied the coprecipitation of softwood Kraft lignin (SKL) and bisphenol A diglycidyl ether (BADGE) with the objective to develop a robust and simple method to stabilize spherical lignin nanoparticles via intraparticle cross-linking. Overall, the mass ratio of BADGE to SKL determines the properties of the hybrid lignin nanoparticles (hy-LNPs) in both particle formation and curing steps. With a well-tuned mass ratio of 1:4 of BADGE to SKL, the hy-LNPs can be efficiently structurally stabilized by intraparticle cross-linking while retaining their surface charge and colloidal stability in aqueous media. The internally cross-linked particles exhibited a strong resistance to dissolution at high pH (e.g., pH 12) and in acetone-water (3:1, w/w) binary solvent as well as improved thermal stability. Covalent cationization was successfully applied to the cross-linked particles via epoxy chemistry under strongly alkaline conditions, resulting in a pH-switchable surface charge of the particles. Furthermore, the hy-LNPs with BADGE content ≥30 wt% demonstrated a high potential as a bio-based waterborne adhesive for wood. We envision that such a design of the waterborne adhesive formulation, that is, encapsulation of the water-insoluble epoxy by lignin in aqueous media and release of the epoxy upon heating or applied pressure could trigger opportunities in the controlled release applications and design of many other resin formulations.
Keywords: hybrid lignin nanoparticle, intraparticle cross-linking, interparticle cross-linking, covalent surface functionalization, lignin-epoxy adhesive, colloidal lignin particle
Reprinted with permission from Solvent-Resistant Lignin-Epoxy Hybrid Nanoparticles for Covalent Surface Modification and High-Strength Particulate Adhesives, Tao Zou, Mika Henrikki Sipponen, Alexander Henn, and Monika Österberg, ACS Nano Article ASAP, DOI: 10.1021/acsnano.0c09500. Copyright 2021 American Chemical Society.