Synthesis of fused conjugated polymers containing imidazo[2,1-b]thiazole units by multicomponent one-pot polymerization

We herein report a facile and efficient multicomponent polymerization approach to construct fused heterocyclic polymers with imidazo[2,1-b]thiazole units in the main chain. A preliminary polymerization reaction was carried out as a model reaction with 1,4-phthalaldehyde, [6,6′-bibenzothiazole]-2,2′-diamine and 1-ethynyl-4-hexylbenzene as monomers, and different polymerization conditions, including the catalyst, catalyst amount and solvent, were optimized. Based on the optimized conditions, a series of fused heterocyclic conjugated polymers containing imidazo[2,1-b]thiazole units with high-molecular weights (Mn up to 5.7 × 104) in moderate yields (up to 54.3%) were obtained. With imidazo[2,1-b]thiazoles embedded in the main chains, the resulting polymers possess outstanding solubility, relatively good thermal stability and low energy bands. A possible mechanism was proposed for the polymerization including a 5-exo-dig cyclization and then an aromatization process.