Solution processable Zn-salphen containing π-conjugated polymers with unique aggregation behavior as organic optoelectronic materials

Abstract

Series of π-conjugated polymers containing electron-withdrawing Zn-Schiff base complex (Zn-salphen) were reported. These polymers can be easily obtained with controllable optical bandgap (Egopt) varying from 1.50 to 2.13 eV by changing the π-conjugated comonomers, and together with excellent thermal stabilities. It was found that the introduction of alkyl chains could provide good solution process-ability for these polymers in chlorobenzene solutions. All the polymers exhibit high hydrophilic characteristics compared to traditional semi-conducting polymers. This is caused by the large polarity of Zn-salphen, which results in strong inter-molecular interactions for the polymers analyzed based on their optical properties. Interestingly, these aggregation behaviors are highly dependent on the type of solvents and coordinating additives such as pyridine, which can be observed from their UV–vis absorption and photoluminescence (PL) spectra. In addition, the film morphologies of these polymers can be modified by using pre- and post-treatments such as thermal annealing, solvent annealing and additives. This work introduces a new strategy for constructing semi-conducting polymers by solving the problem of poor solubility of Zn-salphen complex, and preliminarily studies the feasibility of these Zn-salphen containing polymers regarding their solution process-ability, optical adjustment and morphology optimization. These polymers are considered potential candidates for applications in photoelectric devices.