Influence of donor-acceptor conjugation between thiophene-phthalazinone structures containing Sp³ CN bond on the frontier orbital levels and optic-electronic properties

Abstract

Herein, an electron‐deficient phthalazinone unit containing a unique Sp3 hybrid nitrogen atom as an acceptor to cut off the ether bond was presented and three Donor–Acceptor (D–A) conjugated fluoropolymers via Classical Aromatic Nucleophilic Displacement Polymerization (CANDP) method were successfully synthesized. These polymers exhibit excellent thermostability. The 5% weight loss temperature of PDT2TF under nitrogen atmosphere is high, up to 470 °C. This is due to that the D–A conjugation between thiophene‐phthalazinone units affects its resonance energy and stabilizes the thiophene‐phthalazinone structures. These three fluoropolymers show strong absorptions and fluorescence in visible light region both in solution and thin film states. The band gaps (Eg) of these polymers are narrower than that of their corresponding di‐NH capped monomers, owing to the good electronic communication properties of the Sp3 nitrogen atom in the phthalazinone unit. The Eg value of PDT3TF is decreased to 2.03 eV. These results indicate that phthalazinone unit is an efficient acceptor and could exhibit strong D–A effect with thiophene unit. Also, the Sp3 nitrogen atom in the phthalazinone shows good electronic wave function and charge transport properties. This facile CANDP synthetic method combined with Sp3 CN bond linked electron‐deficient phthalazinone unit affords polymers with controllable photoelectric properties. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3470–3483