No abstract

Trapping lithium polysulfides of a Li–S battery has been successfully demonstrated by forming lithium bonds in a polymer matrix.

Plastic pollution is one of the most pressing global environmental issues we face today, in part due to the continued rise in production and use of disposable plastic products. Polyolefins and polyesters are two of the most prevalent polymers in the world accounting for ∼80% of total nonfiber plastic production. Recycling, despite being intrinsically environmentally friendly and sometimes economically viable, remains at a surprisingly low level (<9% in the U.S.) with most plastic waste ending up in landfills. One reason for this low rate of recycling stems from the challenge of recycling mixed waste streams and multicomponent plastics. In mixed waste streams, physical presorting of components prior to recycling requires significant effort, which translates to added cost. For multicomponent plastics (e.g., multilayer films such as food wrappers), the individual plastic components cannot be efficiently physically separated, and they are immiscible with poor interfacial adhesion when melt reprocessed. Thus, direct recycling of mixed plastics by melt reprocessing results in products that lack desired end-use properties. In this study, we describe the synthesis of novel poly(ethylene terephthalate)−polyethylene multiblock copolymers (PET−PE MBCPs) and evaluate their utility as adhesive tie layers in multilayer films and compatibilizer additives for melt reprocessed blends. PET and PE are targeted because they are two of the most prevalent commercial polymers in the world and are high volume waste streams. The work described here demonstrates two key findings. First, the PET−PE MBCPs serve as effective adhesive tie layers between neat PET/PE films with adhesive strength comparable to that of commercially available adhesives. Second, PET/PE (80/20 wt %) blends containing ∼0.5 wt % PET−PE MBCP were melt mixed to mimic recycling mixed plastic waste, and they were found to exhibit mechanical properties better than neat PET. Overall, this study demonstrates that PET−PE MBCPs could significantly enhance the ability to recycle PET/PE mixed waste streams by serving the role as both an adhesive promoting layer and a compatibilizer additive.

Conventional free radical polymerization with subsequent postpolymerization modification afforded imidazolium copolymers with controlled charge density and side chain hydroxyl number. Novel imidazolium-containing copolymers where each permanent cation contained one or two adjacent hydroxyls allowed precise structure-transfection efficiency studies. The degree of polymerization was identical for all copolymers to eliminate the influence of molecular weight on transfection efficiency. DNA binding, cytotoxicity, and in vitro gene transfection in African green monkey COS-7 cells revealed structure-property-transfection relationships for the copolymers. DNA gel shift assays indicated that higher charge densities and hydroxyl concentrations increased DNA binding. As the charge density of the copolymers increased, toxicity of the copolymers also increased; however, as hydroxyl concentration increased, cytotoxicity remained constant. Changing both charge density and hydroxyl levels in a systematic fashion revealed a dramatic influence on transfection efficiency. Dynamic light scattering of the polyplexes, which were composed of copolymer concentrations required for the highest luciferase expression, showed an intermediate DNA-copolymer binding affinity. Our studies supported the conclusion that cationic copolymer binding affinity significantly impacts overall transfection efficiency of DNA delivery vehicles, and the incorporation of hydroxyl sites offers a less toxic and effective alternative to more conventional highly charged copolymers.

A series of imidazolium-based bis(trifluoromethylsulfonyl)imide [NTf 2 ] poly(ionic liquid)s (PILs) were prepared by conducting the solventless thiol-ene 'click' photopolymerization of bisallylimidazolium [NTf 2 ] and pentaerythritol tetrakis(3-mercaptopropionate) (PTMP). The thiol:ene molar ratio was varied in order to examine changes in the thermal, mechanical and conductive properties of the resulting polymer networks. The 1.0:2.0 thiol-ene PIL network exhibited the highest glass transition temperature (T g of-5.0 °C) and storage modulus (E′ of 9.24 MPa at 100 °C) values. Temperature-dependent ionic conductivities were found to rely on both the T g /crosslink density as well as the IL content, with the highest ionic conductivity observed for the 1.0:3.0 thiol-ene PIL network (1.42 x 10-5 S/cm at 25 °C). Application of Vogel-Fulcher-Tammann and Williams-Landel-Ferry theories revealed the impact of both T g /crosslink density and free ion concentration on temperature-dependent conductivity data, and indicated lower free volumes and fragilities for the thiol-ene networks relative to other non-network PILs.