Solvent-Resistant Lignin-Epoxy Hybrid Nanoparticles for Covalent Surface Modification and High-Strength Particulate Adhesives
Fabrication of spherical lignin nanoparticles (LNPs) is opening more application opportunities for lignin. However, dissolution of LNPs at a strongly alkaline pH or in common organic solvent systems has prevented their surface functionalization in a dispersion state as well as processing and applica...
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Veröffentlicht in: | ACS nano 2021-03, Vol.15 (3), p.4811-4823 |
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Sprache: | eng |
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Zusammenfassung: | Fabrication of spherical lignin nanoparticles (LNPs) is opening more application opportunities for lignin. However, dissolution of LNPs at a strongly alkaline pH or in common organic solvent systems has prevented their surface functionalization in a dispersion state as well as processing and applications that require maintaining the particle morphology under harsh conditions. Here, we report a simple method to stabilize LNPs through intraparticle cross-linking. Bisphenol A diglycidyl ether (BADGE), a cross-linker that, like lignin, contains substituted benzene rings, is coprecipitated with softwood Kraft lignin to form hybrid LNPs (hy-LNPs). The hy-LNPs with a BADGE content ≤20 wt % could be intraparticle cross-linked in the dispersion state without altering their colloidal stability. Atomic force microscopy and quartz crystal microbalance with dissipation monitoring were used to show that the internally cross-linked particles were resistant to dissolution under strongly alkaline conditions and in acetone-water binary solvent that dissolved unmodified LNPs entirely. We further demonstrated covalent surface functionalization of the internally cross-linked particles at pH 12 through an epoxy ring-opening reaction to obtain particles with pH-switchable surface charge. Moreover, the hy-LNPs with BADGE content ≥30% allowed both inter- and intraparticle cross-linking at >150 °C, which enabled their application as waterborne wood adhesives with competitive dry/wet adhesive strength (5.4/3.5 MPa). |
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ISSN: | 1936-0851 1936-086X 1936-086X |
DOI: | 10.1021/acsnano.0c09500 |