Yue Tian-Jun, Ren Bai-Hao, Zhang Wen-Jian, Lu Xiao-Bing, Ren Wei-Min, Darensbourg Donald J
State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Linggong Road, Dalian, 116024, China.
DepartmentDepartment of Chemistry, Texas A&M University, College Station, TX, 77843, USA.
Angew Chem Int Ed Engl. 2021 Feb 19;60(8):4315-4321. doi: 10.1002/anie.202012565. Epub 2020 Dec 21.
Polymeric materials possessing both high refractive indices and high Abbe numbers are much in demand for the development of advanced optical devices. However, the synthesis of such functional materials is a challenge because of the trade-off between these two properties. Herein, a synthetic strategy is presented for enhancing the optical properties of CO -based polycarbonates by modifying the polymer's topological structure. Terpolymers with thiocarbonate and carbonate units randomly distributed in the polymers' main chain were synthesized via the terpolymerization of cyclohexene oxide with a mixture of CO and COS in the presence of metal catalysts, most notably a dinuclear aluminum complex. DFT calculations were employed to explain why different structural sequence were obtained with distinct bimetallic catalysts. Varying the CO pressure made it possible to obtain terpolymers with tunable carbonate linkages in the polymer chain. More importantly, optical property studies revealed that terpolymers with comparable thiocarbonate and carbonate units exhibited a refractive index of 1.501 with an enhanced Abbe number as high as 48.6, much higher than the corresponding polycarbonates or polythiocarbonates. Additionally, all terpolymers containing varying thiocarbonate content displayed good thermal properties with T >109 °C and T >260 °C, suggesting little loss in the thermal stability compared to the polycarbonate. Hence, modification of the topological structure of the polycarbonate is an efficient method of obtaining polymeric materials with enhanced optical properties without compromising thermal performance.
对于先进光学器件的发展而言，同时具备高折射率和高阿贝数的聚合物材料需求量很大。然而，由于这两种性质之间的权衡，合成此类功能材料具有挑战性。在此，提出了一种通过改变聚合物拓扑结构来增强基于CO的聚碳酸酯光学性能的合成策略。在金属催化剂（最显著的是双核铝配合物）存在下，通过环氧环己烷与CO和COS的混合物进行三元共聚，合成了硫代碳酸酯和碳酸酯单元随机分布在聚合物主链中的三元共聚物。采用密度泛函理论（DFT）计算来解释为什么使用不同的双金属催化剂会得到不同的结构序列。改变CO压力使得能够获得聚合物链中碳酸酯键可调节的三元共聚物。更重要的是，光学性能研究表明，具有相当硫代碳酸酯和碳酸酯单元的三元共聚物的折射率为1.501，阿贝数提高到高达48.6，远高于相应的聚碳酸酯或聚硫代碳酸酯。此外，所有含有不同硫代碳酸酯含量的三元共聚物都表现出良好的热性能，玻璃化转变温度（Tg）>109°C，热分解温度（Td）>260°C，这表明与聚碳酸酯相比热稳定性几乎没有损失。因此，改变聚碳酸酯的拓扑结构是一种在不影响热性能的情况下获得具有增强光学性能的聚合物材料的有效方法。
