The copolymerization of carbonyl sulfide (COS) with epoxides has been developed to be a facile method to synthesize well-defined sulfur-containing polymers. This work describes the steric effect of tertiary amines on the copolymerization of COS with propylene oxide (PO) via a zwitterionic approach, using triethyl borane (TEB) accompanied by various tertiary amines. N,N-Dimethylcyclohexylamine accompanied by TEB (1/1) showed an exceedingly high turnover frequency of up to 69 800 h⁻¹ and a copolymer selectivity of up to >99% for organocatalytic COS/PO copolymerization at 60 °C under solvent-free conditions. The obtained poly(propylene monothiocarbonate)s (PPMTC)s have fully alternating sequences, regioregularity of >99% tail-to-head (T–H) content, and high-number average molecular weights of up to 221.8 kg mol⁻¹ and narrow dispersities (1.1–1.3) within 1 min. We disclosed that tertiary amines (pK_a values range from 8.19 to 10.80) with less steric hindrance exhibited higher catalytic activity for COS/PO copolymerization.

中文翻译：

---

用于羰基硫和环氧丙烷共聚的前所未有的高活性有机催化剂：叔胺的位阻效应

羰基硫 (COS) 与环氧化物的共聚已被开发为合成明确定义的含硫聚合物的简便方法。这项工作描述了叔胺通过两性离子方法使用三乙基硼烷 (TEB) 和各种叔胺对 COS 与环氧丙烷 (PO) 共聚的空间效应。N , N -二甲基环己胺伴随着 TEB (1/1) 显示出高达 69 800 h ^{-1 的}极高周转频率在无溶剂条件下，在 60 °C 下有机催化 COS/PO 共聚的共聚物选择性高达 >99%。获得的聚（亚丙基单硫代碳酸酯）（PPMTC）具有完全交替的序列、> 99% 的尾对头（T-H）含量的区域规整性和高达 221.8 kg mol ^{-1 的}高数均分子量和1 分钟内出现窄分散度 (1.1–1.3)。我们公开了具有较小空间位阻的叔胺（p K _a值范围为 8.19 至 10.80）对 COS/PO 共聚表现出较高的催化活性。