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1. 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. 

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2. 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. 

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3. Dithiophosphoric Acids for Polymer Functionalization

   https://doi.org/10.1002/anie.202315963  

   Bao, Jianhua ; Kang, Kyung‐Seok ; Molineux, Jake ; Bischoff, Derek J. ; Mackay, Michael E. ; Pyun, Jeffrey ; Njardarson, Jon T. ( January 2024 , Angewandte Chemie International Edition)

   Dithiophosphoric acids (DTPAs) are an intriguing class of compounds that are sourced from elemental sulfur and white phosphorus and are prepared from the reaction of phosphorus pentasulfide with alcohols. The electrophilic addition of DTPAs to alkenes and unsaturated olefinic substrates is a known reaction, but has not been applied to polymer synthesis and polymer functionalization. We report on the synthesis and application of DTPAs for the functionalization of challenging poly‐enes, namely polyisoprene (PI) and polynorbornene (pNB) prepared by ring‐opening metathesis polymerization (ROMP). The high heteroatom content within DTPA moieties impart intriguing bulk properties to poly‐ene materials after direct electrophilic addition reactions to the polymer backbone introducing DTPAs as side chain groups. The resulting materials possess both enhanced optical and flame retardant properties vs the poly‐ene starting materials. Finally, we demonstrate the ability to prepare crosslinked polydiene films with di‐functional DTPAs, where the crosslinking density and thermomechanical properties can be directly tuned by DTPA feed ratios.

    

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4. Dithiophosphoric Acids for Polymer Functionalization

   https://doi.org/10.1002/ange.202315963  

   Bao, Jianhua ; Kang, Kyung‐Seok ; Molineux, Jake ; Bischoff, Derek J. ; Mackay, Michael E. ; Pyun, Jeffrey ; Njardarson, Jon T. ( January 2024 , Angewandte Chemie)

   Dithiophosphoric acids (DTPAs) are an intriguing class of compounds that are sourced from elemental sulfur and white phosphorus and are prepared from the reaction of phosphorus pentasulfide with alcohols. The electrophilic addition of DTPAs to alkenes and unsaturated olefinic substrates is a known reaction, but has not been applied to polymer synthesis and polymer functionalization. We report on the synthesis and application of DTPAs for the functionalization of challenging poly‐enes, namely polyisoprene (PI) and polynorbornene (pNB) prepared by ring‐opening metathesis polymerization (ROMP). The high heteroatom content within DTPA moieties impart intriguing bulk properties to poly‐ene materials after direct electrophilic addition reactions to the polymer backbone introducing DTPAs as side chain groups. The resulting materials possess both enhanced optical and flame retardant properties vs the poly‐ene starting materials. Finally, we demonstrate the ability to prepare crosslinked polydiene films with di‐functional DTPAs, where the crosslinking density and thermomechanical properties can be directly tuned by DTPA feed ratios.

    

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5. One‐Step Synthesis of Lignin‐Based Triblock Copolymers as High‐Temperature and UV‐Blocking Thermoplastic Elastomers

   https://doi.org/10.1002/ange.202114946  

   Wan, Yi ; He, Jianghua ; Zhang, Yuetao ; Chen, Eugene Y. ‐X. ( December 2021 , Angewandte Chemie)

   This work utilizes frustrated Lewis pairs consisting of tethered bis‐organophosphorus superbases and a bulky organoaluminum to furnish the highly efficient synthesis of well‐defined triblock copolymers via one‐step block copolymerization of lignin‐based syringyl methacrylate andn‐butyl acrylate, through di‐initiation and compounded sequence control. The resulting thermoplastic elastomers (TPEs) exhibit microphase separation and much superior mechanical properties (elongation at break up to 2091 %, tensile strength up to 11.5 MPa, and elastic recovery up to 95 % after 10 cycles) to those of methyl methacrylate‐based TPEs. More impressively, lignin‐based tri‐BCPs can maintain TPEs properties up to 180 °C, exhibit high transparency and nearly 100 % UV shield, suggesting potential applications in temperature‐resistant and optical devices.

    

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