Department of Chemistry, University of British Columbia, Vancouver, British Columbia, Canada.
Dalton Trans. 2017 May 23;46(20):6723-6733. doi: 10.1039/c7dt00990a.
This report describes two different methodologies for the synthesis of aryl end-functionalized poly(lactide)s (PLAs) catalyzed by indium complexes. In the first method, a series of para-functionalized phenoxy-bridged dinuclear indium complexes (NNO)InCl(μ-OPh) (R = OMe (1), Me (2), H (3), Br (4), NO (5)) were synthesized and fully characterized. The solution and solid state structures of these complexes reflect the electronic differences between these initiators. The polymerization rates correlate with the electron donating ability of the phenoxy initiators: the para-nitro substituted complex 5 is essentially inactive. However, the para-methoxy variant, while less active than the ethoxy-bridged complex (NNO)InCl(μ-OEt) (A), shows sufficient activity. Alternatively, aryl-capped PLAs were synthesized via immortal polymerization of PLA with A in the presence of a range of arylated chain transfer agents. Certain aromatic diols shut down polymerization by chelating one indium centre to form a stable metal complex. Immortal ROP was successful when using phenol, and 1,5-naphthalenediol. These polymers were analysed and chain end fidelity was confirmed using H NMR spectroscopy, MALDI-TOF mass spectrometry, and UV-Vis spectroscopy. This study shed light on possible speciation when attempting to generate PLA-lignin copolymers.
本报告描述了两种不同的方法，用于催化铟配合物合成芳基端功能化聚（丙交酯）（PLA）。在第一种方法中，合成了一系列对-官能化的苯氧基桥联双核铟配合物(NNO)InCl(μ-OPh)（R=OMe（1），Me（2），H（3），Br（4），NO（5）），并对其进行了充分的表征。这些配合物的溶液和固态结构反映了这些引发剂之间的电子差异。聚合速率与苯氧基引发剂的供电子能力相关：对位取代的硝基复合物 5 基本上是无活性的。然而，对位甲氧基变体的活性虽然低于乙氧基桥联复合物(NNO)InCl(μ-OEt)（A），但其活性足够高。或者，通过在一系列芳基链转移剂的存在下用 A 对 PLA 进行永生聚合来合成芳基封端的 PLA。某些芳香二醇通过螯合一个铟中心形成稳定的金属配合物来终止聚合。当使用苯酚和 1,5-萘二酚时，永生 ROP 是成功的。这些聚合物使用 1H NMR 光谱、MALDI-TOF 质谱和 UV-Vis 光谱进行了分析，并证实了链端保真度。这项研究为尝试生成 PLA-木质素共聚物时可能的形态提供了一些线索。
