Sulfur-Polymer Nanoparticles: Preparation and Antibacterial Activity.

High sulfur content polymers prepared by inverse vulcanization have many reported potential applications, including as novel antimicrobial materials. High sulfur content polymers usually have limited water-solubility and dispersibility due to their hydrophobic nature, which could limit the development of their applications. Herein, we report the formulation of high sulfur content polymeric nanoparticles by a nanoprecipitation and emulsion-based method. High sulfur content polymeric nanoparticles were found to have an inhibitory effect against important bacterial pathogens, including Gram-positive methicillin-resistant Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa. Salt-stable particles were formulated with the addition of a surfactant, which did not inhibit the antibacterial activity of the polymeric particles. Furthermore, the polymeric nanoparticles were found to inhibit S. aureus biofilm formation and exhibited low cytotoxicity against mammalian liver cells. Interaction of the polymeric particles with cellular thiols could be a potential mechanism of action against bacterial cells, as demonstrated by reaction with cysteine as a model thiol. The findings presented demonstrate methods of preparing aqueous dispersions of high sulfur content polymeric nanoparticles that could have useful biological applications

Selective Hydrogenation of Lignin-derived Aromatics to Give Cyclohexanes with a Rhodium-Pincer Precatalyst

Catalytic hydrogenation of aromatic rings represents an essential industrial chemical process for the synthesis of commodity chemicals and intermediates in pharmaceuticals, polymers, and fine chemicals. Herein, we report an air-stable rhodium complex bearing a pincer bis(oxazolinyl)phenyl ligand that shows good catalytic activity for the hydrogenation of lignin-derived acetophenones, benzoic acids as well as other functionalised aromatics to the corresponding alicyclic products by reducing the aryl groups. The rhodium complex is a precatalyst, offering easy access to active rhodium species, which appears to be heterogeneous in the hydrogenation

Polydopamine-Coated Polymer Nanofibers for In Situ Protein Loading and Controlled Release.

Nanofibrous polymeric materials, combined with protein therapeutics, play a significant role in biomedical and pharmaceutical applications. However, the upload of proteins into nanofibers with a high yield and controlled release has been a challenging issue. Here, we report the in situ loading of a model protein (bovine serum albumin) into hydrophilic poly(vinyl alcohol) nanofibers via ice-templating, with a 100% protein drug loading efficiency. These protein-loaded nanofibers were further coated by polydopamine in order to improve the nanofiber stability and achieve a controlled protein release. The mass ratio between poly(vinyl alcohol) and bovine serum albumin influenced the percentage of proteins in composite nanofibers and fiber morphology. More particles and less nanofibers were formed with an increasing percentage of bovine serum albumin. By varying the coating conditions, it was possible to produce a uniform polydopamine coating with tunable thickness, which acted as an additional barrier to reduce burst release and achieve a more sustained release profile

Antibacterial Activity of Inverse Vulcanized Polymers.

Inverse vulcanization is a bulk polymerization method for synthesizing high sulfur content polymers from elemental sulfur, a byproduct of the petrochemical industry, with vinylic comonomers. There is growing interest in polysulfides as novel antimicrobial agents due to the antimicrobial activity of natural polysulfides found in garlic and onions (Tsao et al. J. Antimicrob. Chemother. 2001, 47, 665-670). Herein, we report the antibacterial properties of several inverse vulcanized polymers against Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa, two common causes of nosocomial infection and pathogens identified by the World Health Organization as priorities for antimicrobial development. High sulfur content polymers were synthesized with different divinyl comonomers and at different sulfur/comonomer ratios, to determine the effect of such variables on the antibacterial properties of the resulting materials. Furthermore, polymers were tested for their potential as antibacterial materials at different temperatures. It was found that the test temperature influenced the antibacterial efficacy of the polymers and could be related to the glass transition temperature of the polymer. These findings provide further understanding of the antibacterial properties of inverse vulcanized polymers and show that such polymers have the potential to be used as antibacterial surfaces

Water-Soluble Ionic Liquid-Containing Sulfur Polymers for Mercury Capture, Demulsification, and Antibacterial Activity

Sulfur polymers, prepared by inverse vulcanization using elemental sulfur and vinylic monomers, are emerging functional materials of current research interest; however, sulfur polymers suffer from limited water solubility due to the hydrophobic nature of conventional comonomers and sulfur. Herein, the preparation of ionic liquid (IL)-containing sulfur polymers are reported using the hydrophilic ionic liquid, 1-allyl-3-vinylimidazolium chloride (AVImCl) as a comonomer. The introduction of IL significantly enhances the hydrophilicity of sulfur polymers, enabling them to dissolve in water. Benefiting from the thorough contact with aqueous mercury ions, the resultant sulfur polymer possesses high uptake capacity (436 mg g−1). After binding mercury, a coordination complex is formed and precipitated. The charged sulfur polymers gain a new application in demulsification. The polymer quickly breaks oil-in-water (O/W) emulsions through anion exchange between Cl− of the polymer and dodecylbenzenesulfonate (DBS−) of the surfactant. In addition, the polymer has a growth inhibitory effect against Staphylococcus aureus. The integration of IL and elemental sulfur provides a novel approach to modifying the wettability of sulfur polymers. Also, this novel water-soluble IL-containing sulfur polymer, with mercury capture, demulsification, and antibacterial activity, can be considered as a multifunctional material in practical water purification.</p

Inverse vulcanisation of self-activating amine and alkyne crosslinkers

Inverse Vulcanisation is a versatile route to the synthesis of high sulfur content polymers. Developments to the field include expanding the variety of organic crosslinker molecules that can be used in the reaction, and the application of catalysis, which lowers the reaction time and the required temperature, as well as improving the yield and properties of the resultant polymers. However, concerns remain that the polymers may have a residual metal content from the catalysts, which is undesirable when considering environmental ramifications. There is also the question of whether the catalyst should be extracted from the polymer, which adds another processing step. Presented here is a study on crosslinkers that contain a non-metallic activating moiety built into their structure, thereby eliminating the aforementioned concerns whilst still providing several benefits. Also explored is the relatively untouched field of using alkynes, rather than alkenes, as crosslinkers, which have the potential to provide much higher crosslink densities in the resultant polymers, which may give favourable properties. The work presented here demonstrates the capability of the self-activating crosslinkers to be used as the sole crosslinker, where they can polymerise below the melting point of sulfur, or as a secondary crosslinker in another reaction, bringing the aforementioned benefits of catalysis.</p