Autopolymerization of 2-bromo-3-methoxythiophene, analysis of reaction products and estimation of polymer structure
R. Nishimura, Y. Hattori, M. Akazawa, J. Kitai, S. Okude, Y. Sakamoto, S. Yamazoe, S. Yokojima, S. Nakamura, K. Uchida
Polymer J. in press
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.