Diacetylenes with Ionic‐Liquid‐Like Substituents: Associating a Polymerizing Cation with a Polymerizing Anion in a Single Precursor for the Synthesis of N‐Doped Carbon Materials

Abstract

Imidazolium- and benzimidazolium-substituted diacetylenes with bromide or nitrogen-rich dicyanamide and tricyanomethanide anions were synthesized and used as precursors for the preparation of N-doped carbon materials. On pyrolysis under argon at 800 °C both halide precursors afforded graphite-like structures with nitrogen contents of about 8.5%. When the dicyanamide and tricyanomethanide precursors were thermolyzed at the same temperature, graphite-like structures were obtained that exhibit nitrogen contents in the range 17-20 wt%; thereby, the benefit of associating a polymerizing cation with a polymerizing anion in a single precursor was demonstrated. On pyrolysis at 1100 °C the nitrogen contents of the latter pyrolysates remain high (ca. 6 wt%). Adsorption measurements with krypton at 77 K indicated that the materials are nonporous. The highest electrical conductivity was observed for a pyrolysate with one of the lowest nitrogen contents, which also has the highest degree of graphitization. Thus, the quest for N-rich carbons with high electrical conductivities should include both maximization of the nitrogen content and optimization of the degree of graphitization. Crystallographic investigation of the precursors and spectroscopic characterization of the pyrolysates prepared by heating at 220 °C indicate that construction of the final carbon framework does not involve the intermediate formation of a polydiacetylene.

Application of Ionic Liquids to Energy Storage and Conversion Materials and Devices

“…The intrinsic nitrogen-containing nature of most ILs offer the possibility to yield NDCs in situ without additional doping agents. Moreover, the structures and properties of the final carbon materials can be easily controlled at the molecular level through rational design of the ionic precursors by virtue of their structural diversity. − Since most conventional ILs under inert atmosphere and ambient pressure afford no suitable carbons due to the lack of stable intermediate polymeric structures and the eventual formation of volatile vapors during thermal decomposition, , the IL precursors being investigated in the early stage are mainly focused on specific ILs containing cross-linkable moieties. , As pioneered by Dai et al in 2009, various intrinsic NDCs were obtained by direct carbonization of aprotic ILs containing nitrile/cyano moieties in either cations or anions. ,,,− Nitrogen heteroatoms are believed to be homogeneously distributed in the obtained NDCs because of the one-step carbonization from a single precursor. The key to successful carbonization of these task-specific ILs in atmospheric pressure is that the nitrile groups undergo cross-linking reactions and form intermediate amorphous polytriazine networks through cyclotrimerization of nitrile groups (Figure ).…”

Symmetrical Diacetylenes Outfitted with Ionic Liquid-like Groups: Structural, Polymerization, and Carbonization Studies

“…This situation is similar to that previously observed for cationic DAs with imidazolium and benzimidazolium substituents. 26,27 Iodide anions are located in channels formed by three DA stacks. The distance between two successive DA cations in these stacks is 6.819 Å, and this distance is the same between iodide anions.…”

“…These results thus show that a temperature of 220 °C is high enough to initiate the formation of a graphitic structure, and this observation is in line with previous results obtained with other diacetylenes. 26,64 Narrowing of the D and G bands is observed with an increase in the thermolysis temperature (Figure 9), which is suggestive of a better crystallinity of the samples due to a decrease in the amounts of defects and/or an increase in the size of the graphitic domains. 77,78,83−86 Also, it is remarkable to note that the degree of graphitization of the materials increases with increasing thermolysis temperature and reaches 2.37 at 1200 °C (Table 2).…”

“…In particular, we reported recently the syntheses of imidazoliumand benzimidazolium-appended diacetylenes with dicyanamide and tricyanomethanide counterions and showed that these compounds did not polymerize in the solid state. 26 Unfortunately, these salts were not meltable, so their polymerization could not be studied in the molten state. However, by replacement of the dicyanamide and tricyanomethanide anions with bromide, it is possible to turn the imidazolium-containing precursor into a photochemically reactive species and prepare an ionic PDA from it.…”

Soft Electronics Based on Liquid Conductors

“…[159][160][161][162] They have been successfully used as electrodes, liquid electrolytes, or interface/current collectors. [163][164][165][166][167] Besides the intrinsic ionic conductivity, wide electrochemical window, high thermal stability, and ultralow volatility allow the ionic liquids at the forefront of liquid electrolytes. Ionic liquids are often used as the precursor to fabricate carbon electrodes, or binders to modify the electrode surfaces.…”