Alkynone-based Multicomponent Tandem Polymerization Toward Conjugated Polymers

Multicomponent Tandem Polymerizations(MCTPs)combine multiple steps into one pot,avoiding the separation and purification of the reactive intermediates,and obtain the final product directly.MCTPs have inherited the advantages of multicomponent reaction(MCRs).Compared with the traditional two-component polymerization,MCTPs have many advantages,such as diversity-oriented,structural tunability,high efficiency,atomic economy,and smooth conditions.At present,MCTPs show great potential and value in constructing functional conjugated polymers.Acetylenes are good substrates with rich chemistry for construction of functional conjugated polymers.As activated electron acceptor,alkyones are reactive intermediates and show great advantages in the synthesis of heteroatom/ heterocyclic conjugated polymers.MCTPs of terminal alkynes,terephthaloyl chloride and hydrazine hydrate/ phenylhydrazine combine three-step Sonogashira coupling/ Micheal addition/ cyclocondensation in one-pot process to gain polypyrazole/ polyphenylpyrazole.By optimizing the solvent,concentration and time,the molecular weights of final polypyrazoles were up to 19.4 kg/mol and the yields were as high as 95%.The polymerization was suitable for various aromatic acetylenes and hydrazines.When the third component was phenylhydrazine,the polyphenylpyrazoles enjoy better solubility and polymerization results,and molecular weights can achieve up to 30.7 kg/mol.The model compounds of 6 and 7 were synthesized to confirm structures of the final polymers.Fortunately,the single crystal structure of 7 was obtained,indicating high regioselectivity of the compound.Compared with monomers,model compound and intermediate polymers,FI-IR spectra,1H MNR spectrums and 13 C MNR spectrums were utilized to characterize the structure of the final polymers.All the polymers have satisfactory solubility,good film-forming ability,thermal stability,high light transmittance,high refractive index and fluorescence properties.One-pot two-step three-component MCTPs of terminal alkynes,terephthaloyl chloride and Fischer’s base were developed to obtain conjugated polydiene-merocyanines.The MCTPs were conducted through Sonogashira coupling/enamine addition sequence.The model compound was synthesized to characterize the structure of the final polymers and the single crystal structure of the model compound 6 was obtained.Compared with monomers,model compound and intermediate polymers,FI-IR spectras,1H MNR spectrums and 13 C MNR spectrums were utilized to fully characterize the structure of the final polymers.It is interesting to note that the model compound presents crystal-induced emission enhancement property.The absolute quantum efficiencies of compound 6 in crystal state is as high as 5 times in film state,up to 37%.