Synthesis of Polyquinolines via One-Pot Polymerization of Alkyne, Aldehyde, and Aniline under Metal-Free Catalysis and Their Properties

A novel synthetic route to polyquinolines with 6-substituted quinoline as the structural unit was developed based on the polymerization of alkyne-aldehyde monomers and aniline derivatives under the catalysis of Lewis acid B(C₆F₅)₃. The polymerization was conducted in dichloroethane at 100 °C for 36 h under air atmosphere, affording polyquinolines with molecular weights up to 13 100 and good solubility in most organic solvents. The substituents in aniline exhibited significant effects on the molecular weight, yield, and solubility of the produced polyquinolines. The structures of prepared polymers were characterized and confirmed by GPC, NMR, and FT-IR. The thermogravimetry (TGA) and differential scanning calorimetry (DSC) analysis suggests that the polyquinolines are highly thermal stable. Further photoluminescence behaviors of the prepared polyquinolines were investigated. Based on the characterization results and small molecule reaction mechanism, the polymerization pathway of the polyquinolines was proposed. Our work has provided a novel simple strategy for the preparation of multifunctional polyquinolines with unique architectures by one-pot synthesis under metal-free catalysis.