Mechanochemical synthesis of inverse vulcanized polymers

Sulfur Conversion to Donor-Acceptor Ladder Polymer Networks through Mechanochemical Nucleophilic Aromatic Substitution for Efficient CO2 Photoreduction

The development of synthetic methods capable of converting elemental sulfur into conjugated porous sulfur-rich polymers remains a great challenge, although direct utilization of this readily available feedstock can significantly enrich its uses and circumvent environmental problems during sulfur storage. We report herein mechanochemical (MC) nucleophilic aromatic substitution (SNAr) that enables sulfur conversion into thianthrene-bridged porous ladder polymer networks with dense donor-acceptor (D-A) molecular junctions. We demonstrate that the key lies in the generation of bent thianthrene units through a solid-state ball-milling condensation reaction between 1,2-dihaloarenes and elemental sulfur. We also show that the assembling of D-A structural motifs into porous networks affords efficient visible-light-driven photocatalytic reduction of carbon dioxide (CO2) with water (H2O) vapor, in the absence of any additional photosensitizer, sacrificial agents or cocatalysts. Exceptional photoinduced charge separation along with boosted exciton dissociation results in a high-performance of carbon monoxide (CO) production rate of 306.1 μmol g-1 h-1 with near 100 % CO selectivity, which is accompanied by H2O oxidation to O2, as confirmed by both experimental and theoretical results. We anticipate this novel MC SNAr approach will advance processing techniques for direct sulfur utilization and facilitate new possibilities for the synthesis of D-A ladder polymer networks with promising potential in photocatalysis.

Metal-ligand interface effect in the chirality transfer from l- and d-glutathione to gold, silver and copper nanoparticles

Glutathione (GSH) plays a pivotal role in numerous physiological and metabolic processes, including the defense of cells against free radicals and metal toxicity. This tripeptide has been combined with several metal nanoparticles to form a metal-organic interface with unique properties. Here, we implement a one-step, high-yield synthesis method to produce ultrasmall gold, silver, and copper nanoparticles in the intermediate size regime between size-selected nanoclusters and plasmonic nanoparticles to be functionalized with l- and d-glutathione, and study the chirality transfer evidenced by the emergent optical activity observed for each case. The distinctive interactions that take place at the metal-ligand interface for each metal are primarily accountable for establishing the properties of this system. In its protonated state, glutathione anchors only by its thiol group to the surface of gold and copper nanoparticles, whilst for silver nanoparticles an additional binding site through the nitrogen atom of the amide group was indicated by XPS data, albeit with a relatively low proportion. This may contribute to the higher anisotropy factor observed in silver-glutathione nanoparticles. Such slight variations in adsorption configuration generate different chiroptical activity, which has been analyzed per energy region using time-dependent DFT calculations, revealing that metal-to-ligand transitions dominate most of the spectra while ligand-to-ligand are also present in the higher energy regime. Moreover, FTIR and CD data together suggest that those dissimilarities also propitiate particular peptide self-assemblies through intermolecular GSH interactions for each metal, which result in supramolecular structures with properties of beta-sheet arrays. This study offers a parallel examination of the chirality of glutathione-functionalized coinage metals, allowing to establish decisive differences that can be tailored to benefit developments in chiral biomedicine and other diverse applications.

Cyclization Polymerization of Elemental Sulfur and Diisocyanate: New Polymerization Toward High-Performance Polymer

The development of polymer materials heavily relies on new polymerization reactions. Herein, we report the discovery of cyclization polymerization of element sulfur (S8) and aliphatic diisocyanate at room temperature with 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) organic base as the catalyst, where the two monomers are covalently linked via the formation of thiadiazolidinone (TDZD) or a cyclic isocyanurate ring. The polymer of S8 and 1,6-diisocyanatohexane (HDI) exhibits remarkable thermal stability and mechanical properties. Particularly, it has exceptionally high adhesion to various substrates in air or under water, e.g., the underwater adhesion strength is as high as ∼26.5 MPa for poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG) and ∼2.3 MPa for poly(tetrafluoroethylene) (Teflon). The cyclization polymerization provides the basis for the synthesis of high-performance polymers with elemental sulfur.

Adding Value into Elementary Sulfur for Sustainable Materials

Sulfur-rich copolymers, characterized by high sulfur contents and dynamic disulfide bonds, show significant promise as sustainable alternatives to conventional carbon-based plastics. Since the advent of inverse vulcanization in 2013, numerous synthesis strategies have emerged - ranging from thermopolymerization and photoinduced polymerization to the use of crosslinkers such as mercaptans, episulfides, benzoxazines, and cyclic disulfides. These advancements coupled with the rising demand for degradable plastics have driven research for diverse applications, including optical windows, metal uptake, and adhesives. Due to the unique electronic properties of sulfur-rich materials, they are promising candidates for cathodes in Li-S batteries and triboelectric nanogenerators. This review highlight the latest exciting ways of synthesis strategy in which sulfur and sulfur-based reactions are bing utilized to produce sustainable materials in energy, optics, engeneering material, environemtal, and triboelectric nanogenerators. Finally, this review provides a forward-looking perspective on the opportunities and challenges shaping this rapidly evolving field.

Dynamic Covalent Sulfur-Selenium Rich Polymers via Inverse Vulcanization for High Refractive Index, High Transmittance, and UV Shielding Materials

Recent advancements in inverse vulcanization have led to the development of sulfur-rich polymers with diverse applications. However, progress is constrained by the harsh high-temperature reaction conditions, limited applicability, and the generation of hazardous H2S gas. This study presents an induced IV method utilizing selenium octanoic acid, yielding sulfur-selenium rich polymers with full atom economy, even at a low-temperatures of 100-120 °C. The resultant sulfur-selenium rich polymers exhibit exceptional optical properties: 1) A high refractive index, reaching 1.89 when the total sulfur-selenium content is 65%; 2) Excellent UV shielding capabilities, blocking ultraviolet rays while permitting 95.1-98.6% transmission of visible light; 3) Notable transparency, with polymer films of 0.94 mm thickness exhibiting good transparency under natural light. The materials also demonstrate environmental stability under prolonged exposure to hot or cold conditions. Additionally, the polymers display adhesive strength as evidenced by two adhered glass slides with the material lifting weights of up to 20 kg without any displacement in their glued area. These properties provide a new avenue for sulfur-selenium rich materials to be implemented in high-precision optical instruments with unique characteristics.

Sodium Thiophenolate Initiated Polymerization of Methacrylate with Sulfur (S8): High-Refractive-Index and -Transparency Polymers for Lithography

A simple and effective strategy for introducing sulfur into a polymethacrylate matrix at room temperature has been developed, allowing for the polymerization of a variety of methacrylate derivatives with sulfur. The resulting S-containing polymers exhibited a high refractive index of up to 1.72 while retaining over 90% transmittance in the visible region. Additionally, when mixed with 3% photo acid generator (PAG) as photoresist, the formulation demonstrated excellent patterning capabilities. Furthermore, the scalable preparation of high-refractive-index polymers (HRIPs) indicates significant potential for fabrication.

Inverse Vulcanization of Aziridines: Enhancing Polysulfides for Superior Mechanical Strength and Adhesive Performance

This study introduces a novel approach to inverse vulcanization by utilizing a commercially available triaziridine crosslinker as an alternative to conventional olefin-based crosslinkers. The model reactions reveal a self-catalyzed ring-opening of "unactivated" aziridine with elemental sulfur, forming oligosulfide-functionalized diamines. The triaziridine-derived polysulfides exhibit impressive mechanical properties, achieving a maximum stress of ~8.3 MPa and an elongation at break of ~107 %. The incorporation of silicon dioxide (20 wt %) enhances the composite's rigidity, yielding a Young's modulus of ~0.94 GPa. Furthermore, these polysulfides display excellent adhesion strength on various substrates, such as aluminum (~7.0 MPa), walnut (~9.6 MPa), and steel (~11.0 MPa), with substantial retention of adhesion strength (~3.3 MPa on steel) at -196 °C. The straightforward synthetic process, combined with the accessibility of the triaziridine crosslinker, emphasizes the potential for further innovations in sulfur polymer chemistry.

Transforming Element Sulfur to High Performance Closed-Loop Recyclable Polymer via Proton Transfer Enabled Anionic Hybrid Copolymerization

The utilization of sulfur has been a global issue. Copolymerization of element sulfur (S8) with other monomers is a promising route to convert it to useful materials but is limited by the comonomers. Here, we report anionic hybrid copolymerization of S8 with acrylate and epoxide at room temperature, where S8 does not copolymerize with epoxide in the absence of acrylate. Yet, the proton transfer from the methyne in acrylate to the oxygen anion enables the ring-opening of the cyclic comonomer and hence the copolymerization. The cyclic comonomers can be expanded to lactone and cyclic carbonate. Specifically, the copolymer of S8 with bisphenl A diglycidyl ether and diacrylate displays mechanical properties comparable to those of most common plastics, namely, it has ultimate tensile strength as high as 60.8 MPa and Young's modulus up to 680 MPa. It also exhibits high UV resistance and good transparency. Particularly, it has excellent UV-induced self-healing, reprocessability and closed-loop recyclability due to the abundant dynamic S-S bonds and ester groups. This study provides an efficient strategy to turn element sulfur into closed-loop recyclable polymer with high mechanical and optical performances.

Investigating the Effect of UV Irradiation and TiO2 Addition on Heavy Metal Adsorption by Inverse Vulcanized Sulfur Polymers

Organomercury contamination in wastewater is a longstanding global concern, prompting the establishment of the Mi-namata Convention in 2013, following the tragic Minamata Bay incident in Japan. Despite numerous proposed solutions, the development of an affordable and convenient adsorbent remains a challenge. Sulfur, being one of the most abundant elements globally, has shown promise in mercury adsorption in previous research. This study delves into the influence of light exposure on the process of mercury adsorption. Our findings reveal that exposure to UV-A wavelengths (315 nm-400 nm), in combination with the addition of titanium dioxide (TiO2), enhances the adsorption capacity of a sulfur-rich polymer. The maximum observed adsorption capacity reached 47 mg/g under these conditions. Notably, the presence of TiO2 and UV exposure did not significantly impact the adsorption of inorganic mercury and gold.

Monomer centred selectivity guidelines for sulfurated ring-opening copolymerisations

Sulfur-containing polymers, such as thioesters and thiocarbonates, offer sustainability advantages, including enhanced degradability and chemical recyclability. However, their synthesis remains underdeveloped compared to that of their oxygen-containing counterparts. Although catalytic ring-opening copolymerization (ROCOP) can provide access to sulfur-containing polymers, these materials often exhibit uncontrolled microstructures and unpredictable properties. A comprehensive model that elucidates the factors determining selectivity in these catalytic reactions is still lacking, despite its central importance for advancing these polymerizations into widely applicable methodologies. In this study, we investigate the factors that lead to selectivity in sulfurated ROCOP across various monomer combinations, including thioanhydrides or carbon disulfide with epoxides, thiiranes, and oxetanes. We find that unwanted by-products primarily arise from backbiting reactions of catalyst-bound alkoxide chain ends, which can be mitigated by (i) selecting monomers that form primary alkoxide of thiolate chain ends, (ii) maximizing ring strain in the backbiting step, and (iii) timely termination of the polymerization. By applying these strategies, the selectivity of the catalytic ROCOP can be controlled and we successfully synthesized perfectly alternating poly(esters-alt-thioesters) from various oxetanes and the highly industrially relevant ethylene oxide. Our study thereby shifts the focus for achieving selectivity from catalyst to monomer choice providing valuable mechanistic insights for the development of future selective polymerizations, paving the way for sulfurated polymers as potential alternatives to current commodity materials.

Productive chemistry induced by mechanochemically generated macroradicals

Large or repeated mechanical loads degrade polymeric materials by accelerating chain fragmentation. This mechanochemical backbone fracture usually occurs by homolysis of otherwise inert C-C, C-O and C-S bonds, generating highly reactive macroradicals. Because backbone fracture is detrimental on its own and the resulting macroradicals can initiate damaging reaction cascades, a major thrust in contemporary polymer mechanochemistry is to suppress it, usually by mechanochemical release of "hidden length" that dissipates local molecular strain. Here we summarize an emerging complementary strategy of channelling mechanochemically generated macroradicals in reaction cascades to form new load-bearing chemical bonds, which enables local self-healing or self-strengthening, and/or to generate mechanofluorescence, which could yield detailed quantitative molecular understanding of how material-failure-inducing macroscopic mechanical loads distribute across the network. We aim to identify generalizable lessons derivable from the reported implementations of this strategy and outline the key challenges in adapting it to diverse polymeric materials and loading scenarios.

The Influence of the Comonomer Ratio and Reaction Temperature on the Mechanical, Thermal, and Morphological Properties of Lignin Oil-Sulfur Composites

Although lignin is a plentiful biomass resource, it continually exists as an underutilized component of biomass material. Elemental sulfur is another abundant yet underutilized commodity produced as a by-product resulting from the refining of fossil fuels. The current study presents a strategy for preparing five durable composites via a simple one-pot synthesis involving the reaction of lignin oil and elemental sulfur. These lignin oil-sulfur composites LOSx@T (where x = wt. % sulfur, ranging from 80 to 90, and T represents the reaction temperature in °C) were prepared via the reaction of elemental sulfur and lignin oil (LO) with elemental sulfur. The resulting composites could be remelted and reshaped several times without the loss of mechanical strength. Mechanical, thermal, and morphological studies showed that LOSx@T possesses properties competitive with some mechanical properties of commercial building materials, exhibiting favorable compressive strengths (22.1-35.9 MPa) and flexural strengths (5.7-6.5 MPa) exceeding the values required for many construction applications of ordinary Portland cement (OPC) and brick formulations. While varying the amount of organic material did not result in a notable difference in mechanical strength, increasing the reaction temperature from 230 to 300 °C resulted in a significant increase in compressive strength. The results reported herein reveal potential applications of both lignin and waste sulfur during the ongoing effort toward developing recyclable and sustainable building materials.

Size Control and Antioxidant Properties of Sulfur-Rich Polymer Colloids from Interfacial Polymerization

High sulfur content polymeric materials, known for their intriguing properties such as high refractive indices and high electrochemical capacities, have garnered significant interest in recent years for their applications in optics, antifouling surfaces, triboelectrics, and electrochemistry. Despite the high interest, most high sulfur-content polymers reported to date are either bulk materials or thin films, and there is a general lack of research into sulfur-rich polymer colloids. Water-dispersed, sulfur-rich particles are anticipated to broaden the range of applications for sulfur-containing materials. In this study, the preparation and size control parameters are presented of an aqueous dispersion of sulfur-rich polymers with the sulfur content of dispersed particles exceeding 75 wt%. Employing polymeric stabilizers with varying hydrophilic-lipophilic balance (HLB), along with changing the rank of inorganic polysulfides, allow for the control of particle size in the range of 360 nm - 1.8 µm. The sulfur-rich colloid demonstrates antioxidant properties in water, demonstrating the potential for the use of sulfur-rich polymeric materials readily removable, heterogeneous radical scavengers.

Structural evolution during inverse vulcanization

Inverse vulcanization exploits S8 to synthesize polysulfides. However, evolution of products and its mechanism during inverse vulcanization remains elusive. Herein, inverse vulcanization curves are obtained to describe the inverse vulcanization process in terms of three stages: induction, curing and over-cure. The typical curves exhibit a moduli increment before declining or plateauing, reflecting the process of polysulfide network formation and loosing depending on monomers. For aromatic alkenes, in the over-cure, the crosslinked polysulfide evolves significantly into a sparse network with accelerated relaxation, due to the degradation of alkenyl moieties into thiocarbonyls. The inverse vulcanization product of olefins degrades slowly with fluctuated relaxation time and modulus because of the generation of thiophene moieties, while the inverse vulcanization curve of dicyclopentadiene has a plateau following curing stage. Confirmed by calculations, the mechanisms reveal the alkenyl groups react spontaneously into thiocarbonyls or thiophenes via similar sulfur-substituted alkenyl intermediates but with different energy barriers.

Modification of Polysulfide Surfaces with Low-Power Lasers

The modification of polymer surfaces using laser light is important for many applications in the nano-, bio- and chemical sciences. Such capabilities have supported advances in biomedical devices, electronics, information storage, microfluidics, and other applications. In most cases, these modifications require high power lasers that are expensive and require specialized equipment and facilities to minimize risk of hazardous radiation. Additionally, polymer systems that can be easily modified by lasers are often complex and costly to prepare. In this report, these challenges are addressed with the discovery of low-cost sulfur copolymers that can be rapidly modified with lasers emitting low-power infrared and visible light. The featured copolymers are made from elemental sulfur and either cyclopentadiene or dicyclopentadiene. Using a suite of lasers with discreet wavelengths (532, 638 and 786 nm) and powers, a variety of surface modifications could be made on the polymers such as controlled swelling or etching via ablation. The facile synthesis and laser modification of these polymer systems were exploited in applications such as direct laser lithography and erasable information storage.

Converting inorganic sulfur into degradable thermoplastics and adhesives by copolymerization with cyclic disulfides

Converting elementary sulfur into sulfur-rich polymers provides a sustainable strategy to replace fossil-fuel-based plastics. However, the low ring strain of eight-membered rings, i.e., S8 monomers, compromises their ring-opening polymerization (ROP) due to lack of an enthalpic driving force and as a consequence, poly(sulfur) is inherently unstable. Here we report that copolymerization with cyclic disulfides, e.g., 1,2-dithiolanes, can enable a simple and energy-saving way to convert elementary sulfur into sulfur-rich thermoplastics. The key strategy is to combine two types of ROP-both mediated by disulfide bond exchange-to tackle the thermodynamic instability of poly(sulfur). Meanwhile, the readily modifiable sidechain of the cyclic disulfides provides chemical space to engineer the mechanical properties and dynamic functions over a large range, e.g., self-repairing ability and degradability. Thus, this simple and robust system is expected to be a starting point for the organic transformation of inorganic sulfur toward sulfur-rich functional and green plastics.

Ring-Opening Terpolymerisation of Elemental Sulfur Waste with Propylene Oxide and Carbon Disulfide via Lithium Catalysis

Elemental sulfur, a waste product of the oil refinement process, represents a promising raw material for the synthesis of degradable polymers. We show that simple lithium alkoxides facilitate the polymerisation of elemental sulfur S8 with industrially relevant propylene oxide (PO) and CS2 (a base chemical sourced from waste S8 itself) to give poly(monothiocarbonate-alt-Sx) in which x can be controlled by the amount of supplied sulfur. The in situ generation of thiolate intermediates obtained by a rearrangement, which follows CS2 and PO incorporation, allows to combine S8 and epoxides into one polymer sequence that would otherwise not be possible. Mechanistic investigations reveal that alkyl oligosulfide intermediates from S8 ring opening and sulfur chain length equilibration represent the better nucleophiles for inserting the next PO if compared to the trithiocarbonates obtained from the competing CS2 addition, which causes the sequence selectivity. The polymers can be crosslinked in situ with multifunctional thiols to yield reprocessable and degradable networks. Our report demonstrates how mechanistic understanding allows to combine intrinsically incompatible building blocks for sulfur waste utilisation.

The key role of unsaturated olefin content on polysulfides prepared via inverse vulcanization of waste plant oils for mercury removal from wastewater

Three waste plant oils (olive oil, coconut oil, and soybean oil) were utilized as monomer crosslinking agents to synthesize polysulfides by inverse vulcanization with elemental sulfur, for mercury removal from wastewater. NMR analysis showed that 92.1% of the olefins participated in the inverse vulcanization reaction, indicating that the quantity of unsaturated olefins in plant oil mainly affects the ring-opening ratio of sulfur for the formation of sulfur-based polymers. The experimental results showed that olive oil polysulfide (S-r-olive) achieved 100% Hg2+ removal within 2 h at a pH of 6. The S-r-olive, S-r-soybean, and S-r-coconut exhibited adsorption capacities of 130.23, 42.72, and 28.08 mg/g, respectively. The kinetic and adsorption isotherm illustrated that the Hg2+ adsorption by polysulfides conformed to the pseudo-second-order and Freundlich models, showing that the reaction rate constant of S-r-olive is approximately 14 times and 4.6 times greater than that of S-r-soybean and S-r-coconut, respectively. The adsorption mechanism is concluded that Hg2+ first enters the suspended S-r-olive by physical adsorption, then combined with sulfur to form HgS by chemical action and fixed in the S-r-olive adsorbent. This study demonstrates that utilizing waste plant oils as monomer crosslinking agents to synthesize adsorbents for Hg2+ removal is feasible and effective.

Step-growth Polymerization of Aziridines with Elemental Sulfur: Easy Access to Linear Polysulfides and Their Use as Recyclable Adhesives

The bulk radical polymerization of bis(aziridine) with molten elemental sulfur resulted in brittle, cross-linked polymers. However, when the bis(aziridine) was treated with elemental sulfur in the presence of an organobase, the ring-opening reaction of aziridine with oligosulfide anions occurred, leading to the formation of linear polymers by step-growth polymerization. These newly synthesized polymers possess repeating units containing a sulfonamide or amide functional moiety and oligosulfide bonds with an average sulfur segment of about two. A small molecular model reaction confirmed the nucleophilic addition reaction of elemental sulfur to aziridine. It was verified that S-S dynamic bond exchange takes place in the presence of an organic base within the linear chains. The mixture of the synthesized polysulfides with pyridine exhibits exceptional adhesive properties when applied to steel, and aluminum substrates. Notably, these prepared adhesives displayed good reusability due to the dynamic S-S exchange and complete recyclability due to their solution processability. This elemental sulfur-involved polymerization approach represents an innovative method for the synthesis of advanced sulfur-containing polymers, demonstrating the potential for various applications in adhesives and beyond.

Mechanochemical Synthesis of Stimuli Responsive Microgels

Mechanochemical approaches are widely used for the efficient, solvent-free synthesis of organic molecules, however their applicability to the synthesis of functional polymers has remained underexplored. Herein, we demonstrate for the first time that mechanochemically triggered free-radical polymerization allows solvent- and initiator-free syntheses of structurally and morphologically well-defined complex functional macromolecular architectures, namely stimuliresponsive microgels. The developed mechanochemical polymerization approach is applicable to a variety of monomers and allows synthesizing microgels with tunable chemical structure, variable size, controlled number of crosslinks and reactive functional end-groups.

Electrochemical Synthesis of Poly(trisulfides)

With increasing interest in high sulfur content polymers, there is a need to develop new methods for their synthesis that feature improved safety and control of structure. In this report, electrochemically initiated ring-opening polymerization of norbornene-based cyclic trisulfide monomers delivered well-defined, linear poly(trisulfides), which were solution processable. Electrochemistry provided a controlled initiation step that obviates the need for hazardous chemical initiators. The high temperatures required for inverse vulcanization are also avoided resulting in an improved safety profile. Density functional theory calculations revealed a reversible "self-correcting" mechanism that ensures trisulfide linkages between monomer units. This control over sulfur rank is a new benchmark for high sulfur content polymers and creates opportunities to better understand the effects of sulfur rank on polymer properties. Thermogravimetric analysis coupled with mass spectrometry revealed the ability to recycle the polymer to the cyclic trisulfide monomer by thermal depolymerization. The featured poly(trisulfide) is an effective gold sorbent, with potential applications in mining and electronic waste recycling. A water-soluble poly(trisulfide) containing a carboxylic acid group was also produced and found to be effective in the binding and recovery of copper from aqueous media.

TM-Free and TM-Catalyzed Mechanosynthesis of Functional Polymers

Mechanochemically induced methods are commonly used for the depolymerization of polymers, including plastic and agricultural wastes. So far, these methods have rarely been used for polymer synthesis. Compared to conventional polymerization in solutions, mechanochemical polymerization offers numerous advantages such as less or no solvent consumption, the accessibility of novel structures, the inclusion of co-polymers and post-modified polymers, and, most importantly, the avoidance of problems posed by low monomer/oligomer solubility and fast precipitation during polymerization. Consequently, the development of new functional polymers and materials, including those based on mechanochemically synthesized polymers, has drawn much interest, particularly from the perspective of green chemistry. In this review, we tried to highlight the most representative examples of transition-metal (TM)-free and TM-catalyzed mechanosynthesis of some functional polymers, such as semiconductive polymers, porous polymeric materials, sensory materials, materials for photovoltaics, etc.

Durable composites by vulcanization of oleyl-esterified lignin

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.