Tuning the Solid State Emission of Thin Films/Microspheres Obtained from Alternating Oligo(3-octylthiophenes) and 2,6-Bis(pyrazole)pyridine Copolymers by Varying Conjugation Length and Eu3+/Tb3+Metal Coordination

Abstract

A series of dialkynyl-functionalized oligo(3-octylthiophene)m (m = 1–7 and 9, where m is the number of thiophene units) were polymerized together with 2,6-bis(pyrazole)pyridine (BPP) to get alternating copolymers (P1–P7 and P9) with the number-average molecular weights (Mn) in the range of 5.3–11 kDa. These copolymers were further self-assembled into solid microspheres. The optical emission range of these copolymers were fine-tuned from blue to red and white by changing the conjugation length of thiophene oligomers (band gap approximately from 2.1 to 1.67 eV) and coordination of metals like Eu3+ and Tb3+ in both the solution and solid states. A white color was obtained in solution, thin film, and microsphere states with CIE (Commission Internationale de l’Eclairage) coordinates close to the values of standard white color.