Nitrogen-doped carbon is a promising metalfree catalyst for oxygen reduction reaction in fuel cells and metal-air batteries. However, its practical application necessitates a significant cost reduction, which can be achieved in part by using new synthetic methods and improvement of catalytic activity by increasing the density of redox active centers. This can be modulated by using polymer as the carbon and nitrogen sources. Although, superior catalytic activity of such N-doped C has been investigated in details, the electrochemical long-term stability of polymer-derived doped-carbon is still unclear. Herein, in this study we generated N-doped carbon from the most recommended polymer that is comparable to the state-of-the-art materials with porosity as high as 2,086 m 2 g -1 and a nitrogen doping level of 3-4 at.%, of which 56 % is pyrrolic N, 36.1 % pyridinic and *8 % graphitic. The electrochemical characterization shows that N-doped carbon is catalytic toward oxygen reduction in an alkaline electrolyte via a favorable four-electron process, however, not stable under long-term potential scanning. The irreversible electrochemical oxidation of this material is associated with the presence of a significant content or pyrrolic and pyridinic N close to the edge of the carbon network originating from the polypyrrole precursor. These structures are less stable under operating electrochemical potential. The role of polypyrrole as the precursor of N-doped carbons has to be carefully revised since it supplies sufficient number of catalytic sites, but also generates unstable functionalities on the carbon surface.

This work demonstrates a rapid and scalable route for the preparation of N‐doped carbon spheres of 80–120 nm via pyrolysis of polypyrrole as the only carbon and nitrogen source. The resulting porous catalyst has a nitrogen doping level of 6–8 at%. Electrochemical studies show that N‐doped C is very active toward oxygen reduction in alkaline electrolyte and the mechanism of ORR process is controlled by the surface concentration of catalytic active sites that promote either a direct four‐electron or two‐electron process. An interesting observation is that we can generate precursors for the N‐doped carbon with desirable particle size, shape and with the preferential structure (linear polypyrrole from the αα coupling during slow polymerization or cross‐linked polypyrrole from αβ coupling during fast polymerization) that promotes the formation of favorable catalytic sites for O2 reduction. The XPS analysis in conjunction with RDE voltammetry highlights the effect of polymer precursor synthesis on the chemical structure and a resulting electrochemical activity of the N‐doped carbon materials.

Alkynyl-terminated polyethylene oxide−tetrahydrofuran (ATPET) and glycidyl azide polymer (GAP) could be linked through click-chemistry between the alkynyl and azide, and the product may serve a binder for solid propellants. The effects of the energetic plasticizers A3 [1:1 mixture of bis-(2,2-dinitropropy) acetal (BDNPA) and bis-(2,2-dinitropropyl) formal(BDNPN)] and Bu-NENA [N-butyl-N-(2nitroxyethyl) nitramine] on the curing reaction between ATPET and GAP have been studied. A diffusion-ordered nuclear magnetic resonance spectroscopy (DOSY-NMR) approach has been used to monitor the change in the diffusion coefficient of cross-linked polytriazole polyethylene oxide−tetrahydrofuran (PTPET). The change in the diffusion coefficient of PTPET with A3 plasticizer is significantly higher than that of PTPET with Bu-NENA. Viscosity analysis further highlighted the difference between A3 and Bu-NENA in the curing process—the curing curve of PTPET (A3) with time can be divided into two stages, with an inflection point being observed on the fourth day. For PTPET (Bu-NENA), in contrast, only one stage is seen. The above methods, together with gel permeation chromatography (GPC) analysis, revealed distinct effects of A3 and Bu-NENA on the curing process of PTPET. X-ray Photoelectron Spectroscopy (XPS) analysis showed that Bu-NENA has little effect on the valence oxidation of copper in the catalyst. Thermogravimetric (TG) analysis indicated that Bu-NENA helps to improve the thermal stability of the catalyst. After analysis of several possible factors by means of XPS, modeling with Material Studio and TG, the formation of molecular cages between Bu-NENA and copper is considered to be the reason for the above differences. In this article, GAP (Mn = 4000 g/mol) was used to replace GAP (Mn = 427 g/mol) to successfully synthesize the PTPET elastomer with Bu-NENA plasticizer. Mechanical data measured for the PTPET (Bu-NENA) sample included ε = 34.26 ± 2.98%, and σ = 0.198 ± 0.015 MPa.

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The ladder phenyl/vinyl polysilsesquioxane (PhVPOSS) was used to improve the flame-retardancy performances of ethylene-vinyl acetate copolymer (EVA)/aluminum hydroxide (ATH) composites due to the reactivity of its vinyl groups. FTIR, XPS, 1H NMR, and SEM-EDS data demonstrated the PhVPOSS grafting onto EVA molecular chains. The PhVPOSS improved the thermal stability of EVA/ATH composites, as shown by the thermogravimetric analysis (TGA). Furthermore, with the cone calorimeter (CONE) experiments, EVA/ATH/PhVPOSS showed better fire safety than the EVA/ATH composites, with the PHRR, PSPR, and PCOP reduced by 7.89%, 57.4%, and 90.9%, respectively. The mechanism investigations of flame retardancy revealed that the charring behaviors of the EVA/ATH/PhVPOSS composites were improved by the formation of Si-C bonds and Si-O bonds, and a more compact and denser char layer can contribute more to the barrier effect.

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Polyether polyurethane elastomers prepared by polyisocyanate N100 and ethylene oxide‐tetrahydrofuran copolymer (PET) were compared to that polytriazole polyethylene oxide‐tetrahydrofuran (PTPET) elastomers prepared by alkynyl‐terminated polyethylene oxide‐tetrahydrofuran (ATPET) and glycidyl azide polymer (GAP) at a comparative molecular weight. The polyether polyurethane (PET‐N100) elastomers turned out to have better mechanical properties than that of PTPET/GAP elastomer. In order to explore the effectiveness of nitrogen‐enriched structures in the field of flame‐retardancy, PET‐N100 and PTPET/GAP elastomers were tested by cone calorimetry. The PET‐N100 elastomer exhibited an inferior performance of flame‐retardancy to that of PTPET/GAP elastomer. Therefore, a modification of the terminal hydroxyl group in GAP with 4,4′‐methylene‐bisphenyl‐isocyanate (MDI) and flame‐retardant diethyl bis(2‐hydroxyethyl) amino methyl phosphonate (DBMAP) was attempted and characterized by FT‐IR, NMR, and gel permeation chromatography. It was found that the synthesized GAP‐MDI‐DBAMP could serve as a novel curing agent for ATPET, which would endow the novel PTPET elastomer a combination of the advantageous properties, that is, the outstanding mechanical properties from PET‐N100 elastomer, favorable flame‐retardancy from PTPET/GAP elastomer and DBAMP. The thermogravimetry analysis/DTG, DSC, tensile strength test, and swelling analysis proved that PTPET/GAP‐MDI‐DBAMP elastomer had excellent thermal stability and mechanical strength.

TPU and flame‐retardant TPU (FR‐TPU) were prepared through a polyaddition reaction with polytetramethylene ether glycol (PTMEG) and 4,4′‐methylene‐bisphenyl‐isocyanate (MDI) by reactive extruding. 1,4‐Butanediol (BDO) and diethyl bis(2‐hydroxyethyl) amino methyl phosphonate (DBAMP) were used as the chain extender in different ratios, respectively, to obtain TPU and flame‐retardant TPU (FR‐TPU)with adjusted molecular weight and mechanical properties. The resulting TPU and FR‐TPU were characterized by FTIR, DSC, TGA, and NMR. A kinetic model based on the data from extrusion process was used to depict the polymerization of TPU. These reactions carried out without any solvent and the residual water showed that the polymerization with BDO could be achieved in 20 minutes, instead, that with DBAMP in 55 minutes while with a similar molecular weight. These results point out that Twin Screw Extrusion Reaction (TSER) is a suitable and convenient way to produce a variety of polymers.