Modulating Two Copper(I)-Catalyzed Orthogonal 鈥淐lick鈥?Reactions for the One-Pot Synthesis of Highly Branched Polymer Architectures at 25 掳C

详细信息    查看全文

• 作者：Craig A. Bell ; Zhongfan Jia ; Jakov Kulis ; Michael J. Monteiro
• 刊名：Macromolecules
• 出版年：2011
• 出版时间：June 28, 2011
• 年：2011
• 卷：44
• 期：12
• 页码：4814-4827
• 全文大小：1460K
• 年卷期：v.44,no.12(June 28, 2011)
• ISSN：1520-5835

文摘

Controlling the rates of orthogonal 鈥渃lick鈥?reactions in one-pot provides a method for designing highly branched macromolecular architectures. In this work, we constructed third generation (G3) dendrimers consisting of a wide range of chemically different polymer building blocks in one pot at 25 掳C. This approach reduced the number of purification and chemical protection steps. Using the model polystyrene (PSTY) building block system, third generation dendrimers could be formed divergently, convergently or in parallel through modulating the Cu(I) activity for the copper(I)-catalyzed azide鈥揳lkyne cycloaddition (CuAAC) and nitroxide radical coupling (NRC) reactions. The parallel approach was the fastest, generating a G3 dendrimer in under 30 min, and the next fastest was the divergent pathway, followed by the very slow (24 h) convergent pathway. The resulting G3 dendrimer could be cleaved at the alkoxyamine sites back to linear polymers by heating the reaction mixture at 120 掳C in the presence of an excess hydroxyl nitroxide. The synthetic utility of this method was further extended to coupling linear telechelic polymer building blocks, consisting of PSTY, P^tBA, PEG, and PNIPAM, to form a range of dendrimers in high yields. Preparative SEC was used to fractionate excess starting reactants and intermediate polymer species from the product dendrimer.