Synthesis of a low-bandgap polymer bearing side groups containing phenoxy radicals

Abstract

Poly(isothianaphthene methine) bearing di-tert-butylphenoxide in the side chain was prepared by reacting isothianaphthene and 3,5-di-tert-butyl-4-hydroxybenzaldehyde in the presence of POCl3. A reference polymer with no hydroxy group in the side chain was also synthesized. Both polymers are characterized by a low-bandgap with value of ca. 1.3 eV obtained by optical absorption spectroscopy, and ca. 1.7 eV estimated from an electrochemical method. After treatment with PbO2 as an oxidizer, phenoxy radicals were generated by oxidation in the polymer side groups. Optical absorption measurements and electron spin resonance (ESR) showed a characteristic signal due to phenoxy radicals. Magnetic properties of the polymer were examined with ESR and superconducting quantum interference device (SQUID) measurements. The results suggested that the polymer shows paramagnetic behavior.