Published in “Nature Communications” (Online Publication, November 30, 2017).
(Polymer Controlled Synthesis, Division of Materials Chemistry)
Assit Prof. Nemoto, T.
(Electron Microscopy and Crystal Chemistry, Advanced Research Center for Beam Science)
Yamago group developed a new method to synthesize hyperbranched polymers (HBPs) in one-pot by using a newly designed bifunctional monomer having hierarchical reactivity.
Polymer materials are indispensable to our modern society and enrich the quality of our lives. While linear polymers are almost entirely used for fabricating polymer materials, HBPs have attracted significant attention due to their advantageous physical properties compared to those of their linear analogues, such as lower intrinsic viscosity, low glass transition temperature, and a large number of terminal groups. While there are several methods already reported to synthesize HBPs, there is no practical or effective method to synthesize HBPs with well-controlled 3D structures.
Prof. Yamago’s group designed a new bifunctional monomer, in which the two groups of a monomer have hierarchical reactivity. Then, the monomer was copolymerized with acrylate monomer under living radical polymerization conditions using organotellurium compounds as a controlling agent. As the designed monomer only serves as a branching point after it’s monomer part has reacted, HBPs with controlled 3D structure are formed. The molecular weight, number of branching points, and branching density are easily controlled by changing the relative amounts of CTA, vinyl telluride, and acrylate monomers and the narrow dispersity is maintained. Furthermore, selective transformations of the living polymer-end enable the introduction of functional groups at the chain-ends.
This method relies on a living polymerization under radical conditions, a wide range of block copolymers and end-functionalized polymers can be synthesized by using the living ends. In addition, a broad range of functional groups is compatible. Since the radical polymerization is the most industrially important method in polymer synthesis, this work opens an avenue for the design of new polymer structures and functional materials based on HBPs.
Figure 2. a) Ideal structure of the seventh-generation of hyperbranched polymer, b) height image, and c) cross-sectional profile obtained by AFM.