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Productive utilization of lignocellulosic biomass is critical to the continued advancement of human civilization. Whereas the cellulose component can be efficiently upconverted to automotive fuel-grade ethanol, the lack of upconversion methods for the lignin component constitutes one of the grand challenges facing science. Lignin is an attractive feedstock for structural applications, in which its highly-crosslinked architecture can endow composite structures with high strengths. Prior work suggests that high-strength composites can be prepared by the reaction of olefin-modified lignin with sulfur. Those studies were limited to ≤5 wt% lignin, due to phase-separation of hydrophilic lignin from hydrophobic sulfur matrices. Herein we report a protocol to increase lignin hydrophobicity and thus its incorporation into sulfur-rich materials. This improvement is affected by esterifying lignin with oleic acid prior to its reaction with sulfur. This approach allowed preparation of esterified lignin–sulfur (ELS) composites comprising up to 20 wt% lignin. Two reaction temperatures were employed such that the reaction of ELS with sulfur at 180 °C would only produce S–C bonds at olefinic sites, whereas the reaction at 230 °C would produce C–S bonds at both olefin and aryl sites. Mechanistic analyses and microstructural characterization elucidated two ELS composites having compressive strength values (>20 MPa), exceeding the values observed with ordinary Portland cements. Consequently, this new method represents a way to improve lignin utilization to produce durable composites that represent sustainable alternatives to Portland cements.
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This content will become publicly available on February 15, 2026
Thermal and Mechanical Properties of Lignin Derivative–Sulfur Composites
ABSTRACT Lignin, comprising 20%–35% of lignocellulosic biomass, is the second most abundant biopolymer after cellulose. As the bioethanol industry expands, the accumulation of lignin by‐products necessitates innovative valorization strategies. This study explores the synthesis and characterization of lignin‐derived composites. Specifically, the reaction of 20 wt. % lignin‐derived guaiacol or syringol with 80 wt. % elemental sulfur gives composites GS80and SS80, respectively. The chemical structures of composites were elucidated using GC–MS,1H NMR, and UV–Vis spectroscopy, revealing the formation of both SCaryland SCalkylbonds. Thermal and morphological analysis (via TGA, DSC, PXRD, and SEM‐EDS) indicated SS80has higher crystallinity and thermal stability than GS80, attributed to a higher degree of crosslinking and a greater content of dark sulfur. Mechanical testing showed SS80exhibits superior compressional and flexural strengths, and enhanced Young's modulus and Shore hardness, compared to GS80. Notably, the mechanical strength parameters for SS80are comparable to those of C62 class bricks used in construction applications. These findings suggest that lignin‐derived composites, particularly those incorporating syringol, can provide viable alternatives to traditional materials in various applications, contributing to both waste valorization and sustainable materials science.
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- Award ID(s):
- 2203669
- PAR ID:
- 10650095
- Publisher / Repository:
- wiley
- Date Published:
- Journal Name:
- Journal of Polymer Science
- Volume:
- 63
- Issue:
- 4
- ISSN:
- 2642-4150
- Page Range / eLocation ID:
- 789 to 799
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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