Conjugated carbazole-thiophene copolymer: Synthesis, characterization and applications

• Copolymers based on 9-ethylcarbazole and 3-hexylthiophene have been synthesized.
• The thermal stability of the copolymer was improved.
• The complex of copolymer and TBB can detect fluorine anion.

Conjugated copolymers based on 9-ethylcarbazole(9EC) and 3-hexylthiophene(3HT) have been synthesized by oxidative polymerization with FeCl3 in hexane, and it is confirmed that 9EC and 3HT molecules were built into the polymer main chain. Although the rate of the 9EC included in copolymers obtained in hexane was high (maximum 47%), the rate of the ones included in copolymers obtained in chloroform and in nitrobenzene were very low (0% in case of chloroform, 5% in case of nitrobenzene). In polymerizing 9EC and 3HT at several temperatures, yield of 3HT/9EC copolymer was 36% at 25 °C, but the one was 0% at 0 °C. The thermal stability of 3HT/9EC copolymer was improved significantly with the presence of 9EC in the polymer main chain. A complex consisting of 3HT/9EC copolymer and tri-n-butylborane (TBB) (1:1) was prepared in THF solution and this complex was confirmed by 11B NMR. By adding fluorine anion to the complex of 3HT/9EC copolymer and TBB in THF solution, the fluorescence intensity was decreased because of increasing concentrations of fluorine anion.

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