Synthesis of Triphenylamine Copolymers and Effect of Their Chemical Structures on Physical Properties

Abstract

A series of charge transporting triphenylamine (TPA) polymers containing 2,1,3-benzothiadiazole (BTH) and/or 3,4-ethylenedioxythiophene (EDOT) unit(s) in the backbone were synthesized via C–N coupling polymerization using a palladium catalyst system. The preparation of the diblock copolymers based on the TPA-polymers was achieved by introducing poly(ethylene oxide) (PEO) at the terminal. Furthermore, the block copolymers selectively functionalized by BTH at the junction point were also prepared. In order to investigate the structural and morphological effect on physical properties, the optical and electrical properties were measured and compared among the homopolymers, random copolymers, and block copolymers. The photoluminescent (PL) spectra of TPA-polymers containing BTH unit were tunable from blue to red-violet color by the amount of BTH unit. The EDOT-containing polymers showed high hole drift mobility up to 1 × 10–3 cm2 V–1 s–1. On the other hand, the mobility of the BTH-containing polymers was affected by the position of the BTH unit in the polymer structure. The polymers with BTH unit randomly involved in the backbone showed low mobility in the order of 10–6–10–5, whereas no decrease in the mobility was observed for the polymers modified by BTH unit at the junction point.