1,3‐Di‐tert‐butylimidazol‐2‐ylidene (NHCtBu), which is one of the typical N‐heterocyclic carbene (NHC), was found to initiate the anionic chain‐growth polymerization of methyl sorbate (MS) in toluene at −20°C. The polymerization was accelerated by an aluminum Lewis acid, that is, methylaluminum bis(2,6‐di‐tert‐butyl‐4‐methylphenoxide) (MAD), to afford cyclic poly(MS)s. Subsequently, thiol‐ene click reactions of poly(MS)s with two different alkanethiols were performed using a photoradical initiator to obtain graft‐like polymers, which was for the microscopic observation of the chains directly by transmittance electron microscope (TEM). The contamination of linear polymers was hardly observed. This means that the polymers synthesized by our synthetic strategy were indeed cyclic polymers. We also compared the theoretical and experimental chain diameter and width for the graft‐like cyclic polymers, where these values were dependent on the molecular weight of the cyclic polymers regulated by the feed monomer/initiator ratio and length of the alkanethiols, respectively.

中文翻译：

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通过N杂环卡宾引发剂的链增长聚合反应直接观察到环状聚山梨酸烷基酯的形成，并且无需极端稀释即可进行闭环

1,3-二叔丁基咪唑-2-亚烷基（NHC t Bu）是典型的N杂环卡宾（NHC）之一，被发现引发了山梨酸甲酯（MS）的阴离子链增长聚合。在-20℃下甲苯。铝路易斯酸即甲基铝双（2,6-二叔丁基）促进了聚合叔丁基-4-甲基苯酚（MAD），得到环状聚（MS）。随后，使用光自由基引发剂进行聚（MS）与两种不同链烷硫醇的硫醇烯点击反应，得到接枝状聚合物，用于通过透射电子显微镜（TEM）直接观察链。几乎没有观察到线性聚合物的污染。这意味着通过我们的合成策略合成的聚合物确实是环状聚合物。我们还比较了接枝状环状聚合物的理论和实验链直径和宽度，其中这些值分别取决于环状聚合物的分子量，该分子量分别受进料单体/引发剂比率和链烷硫醇长度的调节。