The study concerning the physical and chemical properties of thiophene derivatives has received much attention because they are incorporated in natural products, medicines, functional materials, and photoresponsive dyes. The autopolymerization reaction is one of the synthesis methods of polythiophenes using halogenated thiophene derivatives. In this paper, we analyzed the products and reaction mechanism of the polymerization reaction of 2-bromo-3-methoxythiophene by investigating the gas, liquid, and solid states using UV-Vis, electron spin resonance (ESR), gas chromatography/mass spectrometry (GC/MS), elemental analysis, NMR, and FT-IR spectroscopy. Consequently, we found a side reaction of the autopolymerization reaction and estimated that the polymerization reaction mechanism occurred in multiple steps. When we employed the brominated alkoxythiophene as a monomer, hydrogen bromide gas was generated to act not only as a catalyst of the polymerization reaction but also as an acid to cleave the alkoxyl group. The results provide useful information for the design of monomers via autopolymerization. The mechanism of intense autopolymerization reaction of 2-bromo-3-methoxythiophenes spewing brownish gas was clarified from UV-Vis, ESR, GC/MS, elemental analysis, NMR, and FT-IR spectroscopy. The reaction contained the formation of the hydrogen bromide gas during the autopolymerization. The gas induced the cleavage of the methoxy group on the thiophene ring to form the methyl bromide gas as the side reaction. This work provides an important guide for the application of the autopolymerization of thiophene derivatives to design new polymer materials.

中文翻译：

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2-溴-3-甲氧基噻吩的自聚合、反应产物分析和聚合物结构估计

噻吩衍生物的理化性质研究因其广泛应用于天然产物、药物、功能材料和光敏染料等领域而备受关注。自聚合反应是利用卤代噻吩衍生物合成聚噻吩的方法之一。在本文中，我们通过紫外-可见光、电子自旋共振 (ESR)、气相色谱/质谱法研究气态、液态和固态，分析了 2-溴-3-甲氧基噻吩聚合反应的产物和反应机理。 (GC/MS)、元素分析、NMR 和 FT-IR 光谱。因此，我们发现了自聚合反应的副反应，并估计聚合反应机制发生在多个步骤中。当我们使用溴化烷氧基噻吩作为单体时，会产生溴化氢气体，不仅作为聚合反应的催化剂，而且作为酸裂解烷氧基。结果为通过自聚合设计单体提供了有用的信息。紫外-可见、ESR、GC/MS、元素分析、核磁共振和傅立叶变换红外光谱阐明了2-溴-3-甲氧基噻吩剧烈自聚合反应的机理。该反应包括在自聚合过程中形成溴化氢气体。该气体引起噻吩环上的甲氧基裂解，形成甲基溴气体作为副反应。该工作为噻吩衍生物的自聚合应用于设计新型高分子材料提供了重要指导。