Convergent Synthesis of Miktoarm Star-Branched Polymers Using Polymer Anions

5 Convergent Synthesis of Miktoarm Star-Branched Polymers Using Polymer Anions 

DPE moiety was converted to a reactive DPE anion by treatment with cc-BuLi, the coupling step was repeated between the star-branched anion and 7 in the second iteration. An 8-arm A4B4 star was obtained in 60% yield, but not quantitatively. The yield was not improved after several attempts under various conditions. A subsequent repetition of the same synthetic sequence resulted in a 16-arm AgBg star. The reaction yield was significantly reduced to less than 20%. 

Finally, an attempt to synthesize a 64-arm A32B32 star was made by a coupling reaction of the 16-arm AgBg star-branched polymer anion with a core bearing four BnBr functions. The coupling reaction proceeded insufficiently and the target 64-arm A32B32 star was obtained in only a few per cent. 

In conclusion, the synthesis of multiarmed star polymers was not successful by either the repetition of the synthetic sequence or the coupling reaction of the star-branched polymer anion with a multifunctional core. However, it should be mentioned that the methodology is facile and of great value to be able to successfully obtain some synthetically difficult miktoarm star-branched polymers, such as 8-arm A4B4, 16-arm AgBg, 6-arm A2B2C2, and 12-arm A4B4C4 stars. 

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