Random copolymers of 1,2,3-benzotriazole and alkoxy-modified naptho[2,3-b:3,4-b′]dithiophene: Syntheses, characterization and optoelectronic properties

Naphthodithiophene is a thiophene fused naphthalene with a rigid and planar structure with extended pi-conjugation system and due its electron rich nature it has been recently employed in donor -acceptor type conducting polymers. In this study, alkoxy functionalized naphthodithiophene bearing two new random copolymers namely poly4-(5 ''-(5,6-bis(dodecyloxy)naphtho[2,1-b:3,4-b']dithiophen-2-yl)-[2,2':5',2 ''-terthiophen]-5-yl)-2-dode-cyl-7-(thiophen-2-yl)-2H-benzo[d] [1,2,3]triazole (P1) and poly4-(5 ''-(5,6-bis(dodecyloxy)naphtho[2,1-6:3,4b']dithiophen-2-yl)-[2,2':5',2 '':5 '',2 '':5"',2 ''''-guinguethiophen]-5-yl)-2-dodecy1-7-(thiophen-2-yl)-2H-benzo[d] [1,2,3]triazole (P2) were synthesized via Stille coupling reaction in order to monitor the effect of thiophene and bithiophene bridge units on electrochemical and optical properties of the corresponding polymers. As the acceptor moiety in the polymer backbone electron deficient benzotriazole moiety was used. Thiophene and bithiophene units were used as pi-linkers to enhance electron delocalization through polymer chain. Via alkoxy modification, synthesized polymers were highly soluble in common solvents like THF, chloroform, chlorobenzene. Altering it bridge from thiophene bridge to bithiophene, kinetic properties of the polymers were improved. Electrochemical studies revealed that while P1 has only p-dopable nature, P2 has ambipolar character. Change of pi-bridge from thiophene to bithiophene has affected the optoelectronic properties of the polymers in a favorable manner for different application areas. The polymers exhibited low lying highest occupied molecular orbital (-5.40 eV for P1 and -5.30 eV for P2) and moderate band gaps which are 2.05 eV and 2.02 eV for P1 and P2, respectively.(C) 2017 Elsevier B.V. All rights reserved.