Multicomponent Tandem Polymerizations of Aromatic Diynes, Terephthaloyl Chloride, and Hydrazines toward Functional Conjugated Polypyrazoles

Multicomponent tandem polymerizations (MCTPs) of alkynes enjoying concise procedure, operational simplicity, synthetic efficiency, large structural diversity, high atom economy, and environmental benefit are recently developed as efficient strategies to synthesize functional conjugated polymers, which have attracted much attention from polymer scientists. In this work, through combination of Sonogashira coupling–Michael addition–cyclocondensation reactions in a one-pot procedure, an efficient three-component tandem polymerization of alkyne, carbonyl chloride, and hydrazine hydrate was reported to proceed smoothly under mild conditions at room temperature, affording polypyrazoles with high molecular weights (Mw up to 19 400 g/mol) in excellent yields (up to 95%). This MCTP also applies to various aromatic diynes and aromatic hydrazines, producing polypyrazoles with improved solubility and processability, higher Mws of up to 30 700 g/mol, and high yields. Structural characterization of the polymers such as IR, 1H NMR, and 13C NMR spectra suggested total consumption of monomers and complete conversion of the polymer intermediate, proving the desired well-defined structure of polypyrazoles. These polypyrazoles generally enjoy good solubility and film-forming ability, high thermal stability, high light refractivity, and luminescence behavior. Such MCTPs are not just a simple reaction to connect functional units together in a polymer chain; they can also build functional units such as the newly formed multisubstituted heterocyclics embedded in the polymer main chain at the same time.