Conjugated polymers constructed by a novel pyrene-fused polycyclic building block and their applications as organic electronic materials

• Synthesis of a novel fused polycyclic building block for the conjugated polymers.
• Copolymers showed the good coplanarity and the uniform delocalized HOMO.
• Copolymer with an ordered structure exhibited a hole mobility of 0.015 cm2 V−1 s−1.

A large fused polycyclic pyrene derivative with five-membered imidazole rings fused onto pyrene core, 5,11-Bis(5-Bromothiophene-2-yl)-4,10-dioctadecyl-4,10-dihydropyreno[4,5-d:9,10- d′]diimidazole (PBTI), was designed as a new building block for the conjugated polymers. Copolymers of this monomer with vinylene (P1) and thiophene (P2) were synthesized and their physical properties and performance in organic thin film transistors were investigated. Both polymers exhibited highly coplanar backbones, similar lowest unoccupied molecular orbital energy levels at −3.7 ev and the uniform delocalized highest occupied molecular orbital with deep-lying energy levels around −5.7 ev. X-ray diffraction and grazing-incident X-ray diffraction measurements demonstrated that P2 adopted a highly ordered structure, thus giving an enhanced hole mobility of 0.015 cm2 V−1 s−1 in organic thin film transistors.

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