Cyclic polystyrene topologies via RAFT and CuAAC
Cyclic polystyrene topologies via RAFT and CuAAC
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DOI：
10.1039/c2py20505j
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发表时间：
2012-08
影响因子：
4.6
通讯作者：
Md. D. Hossain;D. Valade;Zhongfan Jia;M. Monteiro
中科院分区：
文献类型：
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作者：
Md. D. Hossain;D. Valade;Zhongfan Jia;M. Monteiro
与具有相同分子量的线性聚合物相比，环状聚合物由于其不同的自组装行为和物理性质而引起了人们的兴趣。使用RAFT制造的聚合物制造环状聚合物的例子很少，并且没有将这些环状聚合物偶联在一起形成恒星的报道。在这项工作中，我们展示了一种新的方法，通过RAFT生产环状聚合物，其功能要求进一步耦合形成2臂和3臂星。采用铜催化叠氮-炔环加成（CuAAC）对化学修饰的线性RAFT聚苯乙烯（PSTY）进行环化，得到纯度为95%的环状聚苯乙烯（cPSTY），采用对数正态分布法模拟实验分子量分布。cPSTY上的- oh基团通过两步过程转化为叠氮化物，允许环聚合物通过丙炔醚或三丙炔胺通过CuAAC反应偶联在一起，分别形成2臂和3臂星。当使用传统的配体配合物和溶剂（即在甲苯中的CuBr-PMDETA）时，由于碱基裂解，环臂之间的连接在24 h后完全降解。我们通过将配体改为三唑或在无配体条件下进行反应（即在DMF中进行cur）来克服这一问题。后一种实验条件下的“点击”效率高于82%。我们通过RAFT生产环状聚合物的方法不仅通过环闭合法扩展了环状聚合物的范围，而且允许人们利用这些环状聚合物作为形成更复杂聚合物结构的构建块。
Cyclic polymer have attracted interest due to their different self-assembly behavior and physical properties compared to their linear counterparts with the same molecular weight. There are only a few examples of using polymer made by RAFT to create cyclic polymers, and no reports of coupling these cyclic polymers together to form stars. In this work, we have demonstrated a novel approach to produce cyclic polymers by RAFT with the required functionality for further coupling to form 2- and 3-arm stars. Cyclization of a chemically modified linear RAFT polystyrene (PSTY) using the copper-catalyzed azide–alkyne cycloaddition (CuAAC) gave cyclic polystyrene (cPSTY) with a purity of 95% as determined by simulating the experimental molecular weight distribution using the log-normal distribution method. The –OH group on cPSTY was converted to an azide via a two step procedure, allowing the cyclic polymers to be coupled together using propargyl ether or tripropargylamine via the CuAAC reaction to form the 2- and 3-arm stars, respectively. When the conventional ligand complex and solvent was used (i.e. CuBr–PMDETA in toluene), the linkage between the cyclic arms degraded fully after 24 h due to base cleavage. We overcame this by changing the ligand to a triazole or carrying out the reaction in ligand-free conditions (i.e. CuBr in DMF). These latter experimental conditions gave ‘click’ efficiencies of greater than 82%. Our methodology for producing cyclic polymers by RAFT will not only extend the range of cyclic polymer by the ring closure method but allow one to utilize these cyclic polymers as building blocks in the formation of more complex polymer architectures.