Preparation of magneto-electro-optically active polymer using Fe ionic liquid as electro-magnetic dopant

Abstract

In this research, we report the synthesis of conjugated polymers with magnetism. Electrochemical polymerization in liquid crystal was conducted with 1-butyl-3-methylimidazolium tetrachloroferrate (BMITF), which is a paramagnetic character having a large magnetic susceptibility, as a supporting salt. The polymer films thus obtained had magnetism because BMITF remains in the films as a dopant. Poly(2,2′-bithiophene) and poly(bis-(3,4-ethylenedioxythiophene)) were prepared in nematic or cholesteric liquid crystal with BMITF by electrochemical polymerization. Transcription of the liquid crystal structure was succeeded with a small amount of BMITF. Blush or fingerprint structures were confirmed by polarizing optical microscopy observation. The addition of the excess amount of BMITF broke the structure of the liquid crystal. Poly(2,2′-bithiophene) transcribed the cholesteric liquid crystal structure showed a negative Cotton effect, indicating with left-handed helical structure. Poly(bis-(3,4-ethylenedioxythiophene)) transcribed the cholesteric liquid crystal structure showed a positive Cotton effect, indicating the polymer forms a right-handed helical structure. The X-ray photoelectron spectroscopy measurements, confirming the existence of Fe element in the polymers thus obtained. From the electron spin resonance measurements, the polymers thus obtained showed magnetic activity. This method affords facile synthesis of conjugated polymers with magnetism.