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.