法国图卢兹大学Tsuyoshi Kato及其研究团队在高分子物理化学中取得了一项新进展，他们在环状低聚硅氧烷的开环聚合中实现了不产生环状低聚物。相关论文于2023年9月1日发表在《科学》杂志上。

在硅橡胶的合成中，一个长期未解决的问题是聚合反应产物中有10%~15%的环状低聚硅氧烷的污染，这是由于聚合物链末端“咬尾巴”反应所导致的。这一过程会与环状单体开环聚合时的链延伸过程竞争，被认为是无法避免的，并且时常导致生成热力学控制的反应混合物（聚合物/环状低聚硅氧烷 = 85/15）。

在该研究中，团队报道了在阴离子链末端简单的乙醇配位可以阻止“咬尾巴”的过程，而精心设计的磷正离子可作为自猝灭系统，当配位的乙醇丢失时，在“咬尾巴”过程开始前中止反应。这两类效应的结合使得八元硅氧烷环D4可发生热力学控制的开环聚合反应，且没有环状低聚硅氧烷杂质。

附：英文原文

Title: Ring-opening polymerization of cyclic oligosiloxanes without producing cyclic oligomers

Author: Limiao Shi, Aurélie Boulègue-Mondière, Delphine Blanc, Antoine Baceiredo, Vicen Branchadell, Tsuyoshi Kato

Issue&Volume: 2023-09-01

Abstract: A long-standing problem associated with silicone synthesis is contamination of the polymer products with 10 to 15% cyclic oligosiloxanes that results from backbiting reactions at the polymer chain ends. This process, in competition with chain propagation through ring-opening polymerization (ROP) of cyclic monomers, was thought to be unavoidable and routinely leads to a thermodynamically controlled reaction mixture (polymer/cyclic oligosiloxanes = 85/15). Here, we report that simple alcohol coordination to the anionic chain ends prevents the backbiting process and that a well-designed phosphonium cation acts as a self-quenching system in response to loss of coordinating alcohols to stop the reaction before the backbiting process begins. The combination of both effects allows a thermodynamically controlled ROP of the eight-membered siloxane ring D4 without producing undesirable cyclic oligosiloxanes.

DOI: adi1342

Source: https://www.science.org/doi/full/10.1126/science.adi1342