Synthesis and Study of Donor-Acceptor Conjugated Polymers based on Isoindigo units via Metal Free Aldol Polymerization Strategy

Abstract

The synthesis of donor-acceptor conjugated polymers is challenging due to the dependence on expensive transition-metal catalysts and potentially hazardous reagents, which can have negative environmental effects. Aldol polycondensation provides a promising, metal-free alternative for polymerizing such materials. In this study, we report the synthesis of three polymers, namely AIRI, AICRI and AITRI, through aldol condensation reaction between diformylisoindigo compound and reduced bis-isatins. Photophysical, electrochemical, thermogravimetric, atomic force microscopy (AFM), gel permeation chromatography (GPC), powder X-ray diffraction (PXRD), density functional theory (DFT) calculations, and space charge limited current (SCLC) hole mobility measurements studies were carried out for these polymers. Photophysical and electrochemical studies showed high visible light absorption, with HOMO energy levels around -5.7 eV and LUMO energy levels near -3.7 eV for all polymers. Thermogravimetric analysis (TGA) indicated that the polymers are stable up to approximately 300 °C. The SCLC hole mobilities measured for polymers, AIRI, AICRI and AITRI were 7.13 × 10 -2 , 8.15 × 10 -2 , and 9.38 × 10 -2 cm 2 V -1 S -1 , respectively.