Synthesis of Multiarm Star Polymer Based on HyperbranchedPolyester Core and Poly(ε-caprolactone) Arms and Its Application inUV-Curable Coating

摘要

Hyperbranched polymers have attracted muchattention in the field of UV-curable coatings because of its lowviscosity, highly branched structure, and rich functionalmoieties. However, hyperbranched polymers also have somelimitations. For example, the spherical structure increases thecrosslinking hindrance, resulting in surplus functionalmoieties. In this study, a multiarm star polymer withhyperbranched polyester core and linear polymer arms wassynthesized and used as UV-curable coating. H40, the fourthgeneration of the hyperbranched polyester, was chosen as thecore owing to its low viscosity and high chemical reactivity.Poly(ε-caprolactone) (PCL) arms were introduced toincrease the content of flexible segments and reduce thecross-linking hindrance. The terminal hydroxyls were then replaced with methacrylate groups to endow the star polymer withUV curable ability, yielding HPCLn-M. This multiarm star polymer was considered as a promising candidate to make up for theshortcomings of UV-curable coating made from the hyperbranched polymer. The properties, such as hardness, adhesion, acidresistance, and alkali resistance of cured films were enhanced obviously after the grafting of PCL. Moreover, to further explorethe effect of the length of PCL grafts on the coating, star polymers with different degree of polymerization (DP) weresynthesized. Through the performance tests of cured films, it was found that the multiarm star polymer HPCLn-M could makeup for the limitations of the hyperbranched polymer when the DP of PCL was suitable, and the comprehensive performance ofcured film reached the best when the DP of PCL was 20. Overall, this multiarm star polymer could combine the advantages ofthe hyperbranched polymer and linear polymer and has the potential to be the next environmentally friendly UV-curablecoating.