Hyperbranched Polymers Prepared by Alkyne-based Click Polymerization

超支化聚合物由于其独特的树枝状结构和物理化学性质，已经得到了广泛关注及应用.而基于炔类单体的点击聚合作为一类简单、高效的聚合反应已被广泛用于超支化聚合物的制备.本文对近5年利用叠氮-炔和巯基-炔点击聚合制备超支化聚合物的工作进行了简要综述.其中，Cu（Ⅰ）催化的叠氮-炔点击聚合可制备1, 4-立构规整的超支化聚三唑；Ru（Ⅱ）催化的叠氮-炔点击聚合可制备1, 5-立构规整的超支化聚三唑；活化的炔类单体和叠氮单体的无金属催化点击聚合可得到1, 4-异构体含量高（高达91.7%）的超支化聚合物；而光引发、热引发及自发的巯基-炔点击聚合可制备含硫的超支化聚合物.此外，对所制备的超支化聚合物的功能和应用进行了简单介绍，最后还简单讨论了点击聚合制备超支化聚合物方面的可能发展方向. Hyperbranched polymers, as one kind of three dimensional macromolecules with globular and dendritic architectures, have unique properties of good solubility, low viscosity, topological structure, a lot of functional groups, etc. Over the past decades, the hyperbranched polymers have attracted more and more attention and been widely applied in diverse areas including coatings, additives, biomaterials, supramolecular chemistry, nanoscience and technology, photoelectricmaterials, and so on. Click polymerization with the advantages of facile monomers accessibility, mild reaction conditions and high reaction efficiency has been developed into a sort of powerful polymerization tool for the synthesis of polymers with well-defined molecular structures and advanced functional properties. This method has also been extensively used in the synthesis of hyperbranched polymers. This review mainly summarizes the progress on the synthesis of the hyperbranched polymers via alkyne-based click polymerizations in the last 5 years. The Cu(I)-catalyzed azide-alkyne click polymerization could readily produce 1,4-regioregular hyperbranched polytriazoles, whereas the Ru(II)-catalyzed azide-alkyne click polymerization could generate 1,5-regioregular hyperbranched polytriazoles. Meanwhile, the azide-alkyne click polymerizations under metal-free conditions were also developed through the ingenious design of monomers. Metal-free click polymerization of activated alkyne and azide monomers could efficiently produce hyperbranched polytriazoles with fraction of 1,4-isomers up to 91.7%. The obtained polytriazoles are thermally stable and well soluble in most common solvents, such as tetrahydrofuran, dichloromethane, N,N-dimethyl formamide, dimethyl sulfoxide. Moreover, the photo- and thermo-initiated as well as spontaneous thiol-yne click polymerizations could be used to facilely prepare sulfur-containing hyperbranched polymers. The thiol-yne addition process could be fine-tuned by the control of the polymerization condition, and hyperbranched polymers with diverse topological structures could be provided. The properties and applications including aggregation-induced emission, sensitive explosive detection, self-healing, high refractive index and fluorescent patterning etc, of resultant hyperbranched polymers were also briefly reviewed. In addition, the promising opportunities and directions in this area were also discussed.