Department of Life Science and Applied Chemistry, Graduate School of Engineering, Nagoya Institute of Technology , Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan.
J Am Chem Soc. 2017 Oct 25;139(42):15005-15012. doi: 10.1021/jacs.7b06897. Epub 2017 Oct 16.
A diene-based cyclic polymer has been synthesized by the anionic polymerization of methyl sorbate (MS) by an N-heterocyclic carbene (NHC) in the presence of a bulky aluminum Lewis acid. We first polymerized methyl sorbate (MS) initiated by NHC in N,N-dimethylformamide (DMF) at 25 °C, poly(MS) with a number-average molecular weight (M) of 3.5 × 10 (M/M = 2.1) was obtained with a conversion of 93%. The structure was confirmed by H and C NMR and IR spectra, which revealed that the propagation proceeded via 1,2-addition as well as 1,4-addition. Although the polymerization did not occur in toluene in the absence of any additive, quantitative monomer consumption was observed in the presence of methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD) to afford the poly(MS) with a 1,4-trans structure, 86% of threo diastereoselectivity, and a M of 23.0 × 10 with narrow molecular weight distribution (M/M = 1.1). From the matrix assisted laser desorption/ionization (MALDI-TOF) mass spectra of poly(MS) and the hydrogenated analogue, ring-closing occurred by nucleophilic attack of the anionic propagating center into the adjacent carbon of the α-terminal imidazolimium group to afford cyclic poly(MS). The cyclic formation in the present synthesis system was confirmed by DSC and viscosity measurements.
一种基于二烯的环状聚合物已通过在大体积铝路易斯酸存在下用 N-杂环卡宾 (NHC) 对马来酸甲酯 (MS) 的阴离子聚合合成。我们首先在 25°C 下在 N,N-二甲基甲酰胺 (DMF) 中用 NHC 引发马来酸甲酯 (MS) 聚合，得到数均分子量 (M) 为 3.5×10 的聚(MS)（M/M=2.1），转化率为 93%。结构通过 H 和 C NMR 和 IR 光谱证实，这表明聚合通过 1,2-加成和 1,4-加成进行。尽管在没有任何添加剂的情况下聚合在甲苯中没有发生，但在甲基铝双(2,6-二叔丁基-4-甲基苯氧基)(MAD)的存在下观察到定量的单体消耗，以提供具有 1,4-反式结构、86% threo 非对映选择性和 23.0×10 的 M 的聚(MS)，分子量分布较窄（M/M=1.1）。从聚(MS)和氢化类似物的基质辅助激光解吸/电离 (MALDI-TOF) 质谱中可以看出，环状聚合是通过阴离子聚合中心对α-末端咪唑鎓基团相邻碳的亲核进攻发生的。在本合成体系中环闭通过 DSC 和粘度测量得到证实。
