More Like this

1. Copolymerization of an aryl halide and elemental sulfur as a route to high sulfur content materials

   https://doi.org/10.1039/c9py01706b  

   Karunarathna, Menisha S.; Lauer, Moira K.; Tennyson, Andrew G.; Smith, Rhett C. (March 2020, Polymer Chemistry)

   null (Ed.)

   High sulfur-content materials (HSMs) have been investigated for a plethora of applications owing to a combination of desirable properties and the low cost of waste sulfur as a starting monomer. Whereas extended sulfur catenates are unstable with respect to orthorhombic sulfur (S 8 rings) at STP, oligomeric/polymeric sulfur chains can be stabilized when they are confined in a supporting matrix. The vast majority of reported HSMs have been made by inverse vulcanization of sulfur and olefins. In the current case, a radical aryl halide–sulfur polymerization (RASP) route was employed to form an HSM ( XS81 ) by copolymerizing elemental sulfur with the xylenol derivative 2,4-dimethyl-3,5-dichlorophenol (DDP). XS81 is a composite of which 81 wt% is sulfur, wherein the sulfur is distributed between cross-linking chains averaging four sulfur atoms in length and trapped sulfur that is not covalently attached to the network. XS81 (flexural strength = 2.0 MPa) exhibits mechanical properties on par with other HSMs prepared by inverse vulcanization. Notably, XS81 retains mechanical integrity over many heat-recast cycles, making it a candidate for facile recyclability. This is the first report of an HSM comprising stabilized polymeric sulfur that has been successfully prepared from a small molecular comonomer by RASP. Preparation of XS81 thus demonstrates a new route to access HSMs using small molecular aryl halides, a notable expansion beyond the olefins required for the well-studied inverse vulcanization route to HSMs from small molecular comonomers. 

   more » « less
2. Copolymerization of a Bisphenol a Derivative and Elemental Sulfur by the RASP Process

   https://doi.org/10.3390/suschem1020013  

   Thiounn, Timmy; Lauer, Moira K.; Karunarathna, Menisha S.; Tennyson, Andrew G.; Smith, Rhett C. (September 2020, Sustainable Chemistry)

   null (Ed.)

   Fossil fuel refining produces over 70 Mt of excess sulfur annually from for which there is currently no practical use. Recently, methods to convert waste sulfur to recyclable and biodegradable polymers have been delineated. In this report, a commercial bisphenol A (BPA) derivative, 2,2′,5,5′-tetrabromo(bisphenol A) (Br4BPA), is explored as a potential organic monomer for copolymerization with elemental sulfur by RASP (radical-induced aryl halide-sulfur polymerization). Resultant copolymers, BASx (x = wt% sulfur in the monomer feed, screened for values of 80, 85, 90, and 95) were characterized by thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. Analysis of early stage reaction products and depolymerization products support proposed S–Caryl bond formation and regiochemistry, while fractionation of BASx reveals a sulfur rank of 3–6. Copolymers having less organic cross-linker (5 or 10 wt%) in the monomer feed were thermoplastics, whereas thermosets were accomplished when 15 or 20 wt% of organic cross-linker was used. The flexural strengths of the thermally processable samples (>3.4 MPa and >4.7 for BAS95 and BAS90, respectively) were quite high compared to those of familiar building materials such as portland cement (3.7 MPa). Furthermore, copolymer BAS90 proved quite resistant to degradation by oxidizing organic acid, maintaining its full flexural strength after soaking in 0.5 M H2SO4 for 24 h. BAS90 could also be remelted and recast into shapes over many cycles without any loss of mechanical strength. This study on the effect of monomer ratio on properties of materials prepared by RASP of small molecular aryl halides confirms that highly cross-linked materials with varying physical and mechanical properties can be accessed by this protocol. This work is also an important step towards potentially upcycling BPA from plastic degradation and sulfur from fossil fuel refining. 

   more » « less
3. Facile new approach to high sulfur-content materials and preparation of sulfur–lignin copolymers

   https://doi.org/10.1039/c9ta10742h  

   Karunarathna, Menisha S.; Tennyson, Andrew G.; Smith, Rhett C. (January 2020, Journal of Materials Chemistry A)

   null (Ed.)

   This report introduces a new approach to high sulfur-content materials. This route, RASP (radical-induced aryl halide/sulfur polymerization), expands the substrate scope beyond olefins required for the traditional inverse vulcanization route to such materials. RASP allows direct reaction of two unmodified industrial waste products to give lignin–sulfur composites. 

   more » « less
4. Differential modes of crosslinking establish spatially distinct regions of peptidoglycan in Caulobacter crescentus

   https://doi.org/10.1111/mmi.14199  

   Stankeviciute, Gabriele; Miguel, Amanda V.; Radkov, Atanas; Chou, Seemay; Huang, Kerwyn Casey; Klein, Eric A. (February 2019, Molecular Microbiology)

   Summary The diversity of cell shapes across the bacterial kingdom reflects evolutionary pressures that have produced physiologically important morphologies. While efforts have been made to understand the regulation of some prototypical cell morphologies such as that of rod‐shapedEscherichia coli, little is known about most cell shapes. ForCaulobacter crescentus, polar stalk synthesis is tied to its dimorphic life cycle, and stalk elongation is regulated by phosphate availability. Based on the previous observation thatC. crescentusstalks are lysozyme‐resistant, we compared the composition of the peptidoglycan cell wall of stalks and cell bodies and identified key differences in peptidoglycan crosslinking. Cell body peptidoglycan contained primarily DD‐crosslinks betweenmeso‐diaminopimelic acid and D‐alanine residues, whereas stalk peptidoglycan had more LD‐transpeptidation (meso‐diaminopimelic acid‐meso‐diaminopimelic acid), mediated by LdtD. We determined thatldtDis dispensable for stalk elongation; rather, stalk LD‐transpeptidation reflects an aging process associated with low peptidoglycan turnover in the stalk. We also found that lysozyme resistance is a structural consequence of LD‐crosslinking. Despite no obvious selection pressure for LD‐crosslinking or lysozyme resistance inC. crescentus, the correlation between these two properties was maintained in other organisms, suggesting that DAP‐DAP crosslinking may be a general mechanism for regulating bacterial sensitivity to lysozyme. 

   more » « less
5. Reactivity of Biomass‐Derived Olefins with Elemental Sulfur: Mechanistic Insight

   https://doi.org/10.1002/ejoc.202301269  

   Kapuge_Dona, Nawoda_L; Maladeniya, Charini_P; Smith, Rhett_C (March 2024, European Journal of Organic Chemistry)

   Abstract Lignocellulosic biomass remains underutilized despite its annual production in gigaton quantities. Sulfur is another vastly underutilized waste product of fossil fuel refining. New mechanistic insight into the reactions of sulfur unveiled since 2020 suggest a rich and hitherto unexplored chemistry between biomass‐derived olefins and elemental sulfur. In this study, four biomass‐derived olefins (eugenol (1), 4‐allyl‐2,6‐dimethoxyphenol (2),o‐eugenol (3), and 2‐allyl‐6‐methylphenol(4)) were reacted with elemental sulfur to elucidate the S−C bond‐forming and other reactivity of these compounds. Each of the compounds was reacted with elemental sulfur in three sulfur : organic reactant ratios (2 : 1, 4 : 1 and 9 : 1) and at two temperatures (180 °C or 230 °C). Product mixtures were characterized using¹H NMR spectrometry and GC‐MS analysis. Products resulting from a range of mechanisms were unveiled, including inverse vulcanization, S−C_{allylic/benzylic}bond formation, S−C_arylbond formation, intramolecular cyclization, C−C σ‐bond scission, and C−O σ‐bond scission. It is anticipated that the insights from this study will support further synergy between the critical sustainability goals of biomass and sulfur utilization. 

   more » « less