兰州大学邬金才团队报道了手性环二酯的对映异构位辅助链端控制立体定向交替共聚。相关研究成果发表在2024年10月28日出版的《德国应用化学》。

不同手性环酯的立体选择性交替共聚，是丰富共聚酯结构多样性和定制其性能的一种可行方法。然而，不同环酯的反应性存在显著差异，这使得这些环酯的完全立体定向交替聚合成为一个挑战，因此需要催化剂来平衡它们的反应性。

该文中，研究人员发现了对映体位点对链端控制的显著影响，并成功地用于平衡高反应性S，S-丙交酯（S，S-LA）和低反应性R，R-乙交酯（R，R-EG）/R，R-丙交酯。R，R-SalenAl配合物的对映体位点可以提高R，R-EG/R，R-PG的相对反应性，抑制S，S-LA的相对反应活性，从而实现S，S-LA/R-EG/R，R-PG共聚物的完美交替序列（Palt=0.96/0.91）。

相反，使用S，S-SalenAl配合物时，显著的对映体位点效应扩大了两种单体的反应性差异，交替水平仅为0.70/0.68甚至0.61。具有高交替规则性的聚（S，S-LA-alt-R，R-EG）表现出较低的玻璃化转变温度，和显著较高的断裂伸长率（εB=449±51%（Palt=0.96）vsεB=6±1%（Palt=0.70））。

附：英文原文

Title: Enantiomorphic Site-Assisted Chain End Control Stereospecific Alternating Copolymerization of Chiral Cyclic Diesters

Author: Ji Xian, Hao Chen, Ge Yao, Fei Chen, Zhichun Chen, Hongzhang Cao, Luya Cao, Xiaobo Pan, Yu Tang, Jincai Wu

Issue&Volume: 2024-10-28

Abstract: Stereospecific alternating copolymerization of different chiral cyclic esters is one feasible approach to enrich the structural diversity of copolyesters and tailor their properties. However, dramatically different reactivities of different cyclic esters let a perfectly stereospecific alternating polymerization of these cyclic esters be a challenge, thus the catalyst is required to balance their reactivities. Herein, a remarkable enantiomorphic site effect on chain end control was discovered and successfully utilized to balance the reactivities of highly reactive S, S-lactide (S, S-LA) and low reactive R, R-ethylglycolide (R, R-EG)/R, R-propylglycolide (R, R-PG) during their heterospecific alternating copolymerization. The enantiomorphic site of R, R-SalenAl complex can increase the relative reactivity of R, R-EG/R, R-PG and suppress that of S, S-LA, then a perfectly alternating sequence of the copolymer of S, S-LA and R, R-EG/R, R-PG can be achieved (Palt = 0.96/0.91); inversely, using S, S-SalenAl complex, the significant enantiomorphic site effect enlarges the reactivity difference of two monomers, the alternating level was just 0.70/0.68 even to 0.61. Poly(S, S-LA-alt-R, R-EG) with a high alternating regularity exhibits lower glass transition temperatures and a dramatically higher elongation at break (εB = 449 ± 51% (Palt = 0.96) vs εB = 6 ± 1% (Palt = 0.70)).

DOI: 10.1002/anie.202420316

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202420316