A cyclic polymethacrylate was prepared via the anionic polymerization of methyl methacrylate (MMA) initiated by a 1:1 adduct of methyl sorbate (MS) and a N-heterocyclic carbene (NHC) without the need for highly dilute conditions, because an α-terminal imidazolimium group is neighboring to the propagating anion during the polymerization. The polymerization proceeded quantitatively using methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD) as the Lewis acid to give the poly (MMA) with the MS unit in the α-terminus, and an M_n of 7.2 × 10³–29.1 × 10³ with a molecular weight distribution (M_w/M_n = 1.1₆-1.5₆). From proton (¹H) NMR and matrix assisted laser desorption/ionization (MALDI-TOF) mass spectra, coupled with size exclusion chromatography (SEC) of the poly (MMA) produced before and after ozonolysis of the internal carbon-carbon double bond in the MS unit, we found that ring-closing reaction was induced by nucleophilic substitution of the propagating anion to the neighboring carbon of the α-terminal carbenyl (imidazolimium) group to synthesize cyclic poly (MMA) following complete the monomer consumption.

通过甲基丙烯酸甲酯（MMA）的阴离子聚合反应制备了环状聚甲基丙烯酸酯，该反应是由山梨酸甲酯（MS）和N-杂环卡宾（NHC）的1：1加合物引发的，因为α-末端不需要很高的稀释条件咪唑啉鎓基团在聚合过程中与正在传播的阴离子相邻。聚合的进行定量使用甲基铝双（2,6-二-叔丁基-4-甲基苯酚）（MAD）作为路易斯酸，得到的聚（MMA）与在α末端的MS单元和中号_Ñ分子量分布为7.2×10 ³ –29.1×10 ³（M _w / M _n  = 1.1 ₆-1.5 ₆）。根据质子（¹ H）NMR和基质辅助激光解吸/电离（MALDI-TOF）质谱，结合对内部碳-碳双键进行臭氧分解前后产生的聚（MMA）的尺寸排阻色谱（SEC）在MS单元中，我们发现闭环反应是通过将阴离子的传播亲核取代到α-末端碳烯基（咪唑啉鎓）基团的相邻碳原子上来进行的，从而在单体完全消耗后合成了环状聚（MMA）。