Alkynone-Based Multicomponent Tandem Polymerization

In contrast with traditional polymerization methodologies, novel multicomponent polymerizations developed in recent years inherit the superiority of multicomponent reactions, such as mild condition, high efficiency, simplified operation, readily tunable structure and environmental benefit etc. thereby they are widely applied in fabrication of various functional polymer materials. Since the emergence of electro-conductive polymer, alkynes are frequently used as building block for synthesis of conjugated or heterocyclic polymers. Till now, alkyneemployed multicomponent polymerizations are rare, however, the alkynone-based multicomponent tandem reactions are increasingly reported over the past decade, attributing to the easy synthesis and the high reaction activity of alkynone. In this thesis, we mainly focus on the development of the alkynone-based multicomponent tandem polymerization and the luminescent properties of the obtained materials.By combining the Sonogashira coupling and Michael reactions, we creatively established a novel three component tandem reaction among alkyne, carbonyl chloride and thiol. This reaction was conducted under mild condition with high efficiency and excellent stereoselectivity up to 89%. Further, this reaction was developed to a corresponding multicomponent tandem polymerization, and poly-(thioether propenone) with high molecular weight(Mw = 57 900 g/mol) and good stereoselectivity was obtained in high yield(96%) under optimized reaction conditions. By changing the functional group numbers of monomers, three linear polymers possess different backbone structures have been obtained. Additionally, this multicomponent tandem polymerization is generally applicable to both aliphatic and aromatic thiols. These polymers possess good solubility and film-forming ability, and their thin film enjoy high refractivity up to n632.8 = 1.7338, which can be modulated by UV irradiation. While both micro- and macromolecules we produced are non-emission, a very special fluorescence enhancement induced by UV irradiation and oxidation of mCPBA were observed instead.We further developed a novel polymerization based on the reported three component tandem reaction among N-(2-iodophenyl)-3-phenylpropiolamide, alkyne and amine. Polyindolin-2-one was obtained in high yield(97%) with satisfactory molecular weight Mw = 18 500 g/mol under optimized polymerization conditions. Thanks to the strong intramolecular π-π interaction among phenyl rings, poly-indolin-2-ones exhibit sole stereoselctivity. Our research results indicated that sterically less crowded alkyne monomers with electron-withdrawing groups were beneficial to improvement of molecular weight. While the model compounds are red crystal-induced emission(CIE) fluorogens, the synthesized polymers are non-fluorescent in solid state as well as solution due to the poor crystallization ability. The advantage of this multicomponent tandem polymerization is that the core functional group-indolinone was generated during the reaction process without synthesis of complicated precursor, causing reduction of operational steps.During the exploitation of novel multicomponent polymerization, we surprisingly found that micromolecular compound PPQE possesses CIE feature and three different crystal forms. Then, the structure-property relationships between single-crystal structures and photophysical properties of PPQE polymorphs were rationally interpreted. In situ and direct observation of the single-crystal-to-single-crystal transformation, amorphous to crystal transformation and crystal formation processes of PPQE were achieved, owning to the extremely low background emission from solution, high-contrast phase boundary and the accompanied fluorescent color and intensity changes. It is indicated that the kinetically isolated crystal A and C were destined to the thermodynamic stable crystal form B promoted by solvent, obeying the Ostwald rule. Fluorescence visualization of dynamic phase transition processes is beneficial for deepening the insight into their underlying mechanisms.According to our acquired experience during the exploitation of novel alkynone-based multicomponent tandem polymerizations, we found they are very excellent in reactional designability and tunable structure of polymer, and fabrication of novel functional polymers with luminescent units generated from simple or commercial monomers.