Petroleum pitch M-50 (or A-240) has been well-known in making valuable carbon materials through thermal treatments. How these molecules react to produce carbon materials and the mechanisms of thermal polymerization and molecular weight growth under thermal conditions are of great significance and yet still unclear. Structures produced by thermal reactions of M-50 pitch were characterized with non-contact atomic force microscopy and compared to the structures in M-50 pitch previously characterized (Chen, P.; Metz, J. N.; Mennito, A. S.; Merchant, S.; Smith, S. E.; Siskin, M.; Rucker, S. P.; Dankworth, D. C.; Kushnerick, J. D.; Yao, N.; Zhang, Y. Petroleum pitch: Exploring a 50-year structure puzzle with real-space molecular imaging. Carbon 2020, 161, 456−465, DOI: 10.1016/j.carbon.2020.01.062). Reaction products were generated from M-50 pitch by two different approaches: an ex situ approach via thermal treatment at 400 °C under N₂ and an in situ approach via reaction directly on a Cu(111) surface. Polycyclic aromatic hydrocarbons (PAHs) from the ex situ reaction are larger than those in the starting M-50 pitch and with fewer methyl groups. Both types of five membered rings, conjugated and non-conjugated, are observed. Very large PAHs are formed under the in situ surface conditions as a result of reactions catalyzed by the Cu surface, with five-membered rings preserved as planar moieties in the product. The data suggest that methyl groups play important roles in initiating the polymerization and molecular weight growth of M-50 pitch molecules, but the reactivities of five-membered rings remain unclear.

中文翻译：

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非接触式原子力显微镜揭示的 M-50 螺距的异位和原位热转变

石油沥青 M-50（或 A-240）以通过热处理制造有价值的碳材料而闻名。这些分子如何反应产生碳材料以及在热条件下热聚合和分子量增长的机制具有重要意义，但仍不清楚。M-50 沥青热反应产生的结构用非接触式原子力显微镜表征，并与先前表征的 M-50 沥青结构进行比较（陈，P。梅斯，JN；门尼托，AS ; 商人，S。史密斯，东南；西斯金，M。立克，SP；丹克沃思，直流；库什内里克，法学博士；姚，N。张，Y.石油沥青：用实空间分子成像探索 50 年的结构难题。碳 2020 , 161 , 456−465, DOI: 10.1016/j.carbon.2020.01.062)。一个：反应产物从M-50的间距由两种不同的方法生成易地通过热处理在氮气氛下400℃的方法₂和一个在原位通过直接在Cu（111）表面反应方法。来自异位反应的多环芳烃 (PAH)比起始 M-50 沥青中的多，并且甲基基团较少。观察到共轭和非共轭的两种类型的五元环。非常大的多环芳烃在原位下形成由 Cu 表面催化的反应导致的表面条件，其中五元环保留为产品中的平面部分。数据表明，甲基在引发 M-50 沥青分子的聚合和分子量增长中起重要作用，但五元环的反应性仍不清楚。