Synthesis and study of donor–acceptor conjugated polymers via a metal free aldol condensation polymerization strategy

Abstract

The development of donor–acceptor conjugated polymers is a challenge due to the involvement of costly transition-metal catalysts and hazardous reagents during the synthesis of such materials, which may potentially cause serious environmental problems. Aldol polycondensation is a promising, metal-free polymerization method to synthesize such donor–acceptor conjugated polymers. Herein, we report the synthesis of three new symmetrical diformyl functionalized thiophene-capped carbazole, fluorene and indolocarbazole moieties. The polymers, ACRBI, AFRBI and AICRBI, were synthesized by aldol condensation reaction between the diformyl compounds and bis(indolinone). Photophysical, electrochemical, and thermogravimetric analyses, gel permeation chromatography, DFT calculations and SCLC hole mobility measurements were performed for these polymers. The photophysical and electrochemical studies of these polymers revealed high visible light absorptivity with a HOMO energy level close to −5.5 eV and a low-lying LUMO energy level close to −3.35 eV. The SCLC hole mobilities of polymers ACRBI, AFRBI and AICRBI were determined to be 4.9 × 10⁻³, 6.7 × 10⁻², and 1.7 × 10⁻³ cm² V⁻¹ S⁻¹, respectively.