Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, U.K.
J Am Chem Soc. 2022 Apr 20;144(15):6882-6893. doi: 10.1021/jacs.2c01225. Epub 2022 Apr 7.
Poly(ester--ethers) can combine beneficial ether linkage flexibility and polarity with ester linkage hydrolysability, furnishing fully degradable polymers. Despite their promising properties, this class of polymers remains underexplored, in part due to difficulties in polymer synthesis. Here, a catalyzed copolymerization using commercially available monomers, butylene oxide (BO)/oxetane (OX), tetrahydrofuran (THF), and phthalic anhydride (PA), accesses a series of well-defined poly(ester--ethers). A Zr(IV) catalyst is reported that yields polymer repeat units comprising a ring-opened PA (), followed by two ring-opened cyclic ethers () (-- or --). It operates with high polymerization control, good rate, and successfully enchains epoxides, oxetane, and/or tetrahydrofurans, providing a straightforward means to moderate the distance between ester linkages. Kinetic analysis of PA/BO copolymerization, with/without THF, reveals an overall second-order rate law: first order in both catalyst and butylene oxide concentrations but zero order in phthalic anhydride and, where it is present, zero order in THF. Poly(ester--ethers) have lower glass-transition temperatures (-16 °C < < 12 °C) than the analogous alternating polyesters, consistent with the greater backbone flexibility. They also show faster ester hydrolysis rates compared with the analogous polymers. The Zr(IV) catalyst furnishes poly(ester--ethers) from a range of commercially available epoxides and anhydride; it presents a straightforward method to moderate degradable polymers' properties.
聚（酯-醚）可以将醚键的灵活性和极性与酯键的可水解性结合起来，从而提供完全可降解的聚合物。尽管它们具有很有前景的特性，但由于聚合反应合成方面的困难，这一类聚合物的研究仍不够充分。在这里，使用商业上可获得的单体丁烯氧化物（BO）/环氧乙烷（OX）、四氢呋喃（THF）和邻苯二甲酸酐（PA），通过催化共聚作用，得到了一系列结构明确的聚（酯-醚）。报道了一种 Zr（IV）催化剂，它可以得到包含开环 PA（）的聚合物重复单元，然后是两个开环的环状醚（）（--或--）。该催化剂具有较高的聚合控制能力、良好的反应速率，并且成功地将环氧化物、环氧乙烷和/或四氢呋喃进行共聚，提供了一种简单的方法来调节酯键之间的距离。对含有/不含有 THF 的 PA/BO 共聚反应的动力学分析表明，该反应遵循总体的二级速率定律：催化剂和丁烯氧化物浓度均呈一级，而邻苯二甲酸酐浓度呈零级，并且当 THF 存在时，THF 浓度也呈零级。与类似的交替聚酯相比，聚（酯-醚）的玻璃化转变温度较低（-16°C < < 12°C），这与其较大的主链灵活性一致。与类似的 聚合物相比，它们的酯水解速率也更快。该 Zr（IV）催化剂可以从一系列商业可得的环氧化物和酸酐中制备聚（酯-醚）；它提供了一种简单的方法来调节可降解聚合物的性能。
