Durable Cellulose–Sulfur Composites Derived from Agricultural and Petrochemical Waste

Nature provides a rich panoply of structural motifs comprised of composites whose mechanical properties exceed those of their individual components. The human endeavor to likewise craft value‐added structural materials from underappreciated, sustainably sourced feedstocks remains a formidable challenge. Herein, efforts are made to achieve durable composites by synergistic combination of sulfur and cellulose. Composites are achieved in which bulk sulfur is reinforced by a network of 1–20% by mass cellulose cross‐linked with polysulfide chains. Composites described herein are remeltable and have flexural strength exceeding that of Portland cement. A thorough analysis of these materials has been undertaken through nuclear magnetic resonance, infrared spectroscopy, Raman spectroscopy, elemental analysis, thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. These analyses of both as‐prepared composites and fractionated materials unequivocally validate the formulation of these composites and the separability of the bulk sulfur from the reinforcing polysulfide‐cross‐linked cellulose network. The thermomechanical properties of these recyclable composites portend their tantalizing potential to supplant inherently unsustainable structural elements in numerous commercial applications. Further applications to improve the environmental resistance and flexural strength of Portland cement by treatment with the sulfur–cellulose composites are also discussed. Cellulose and sulfur are the two most‐produced waste products of agriculture and petroleum refining, respectively. Here, the two waste materials are combined to form composites having flexural strength and resilience on par with those of Portland cement. These composites can also protect Portland cement from water uptake and degradation by acid.