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Ring-Opening Alternating Copolymerization of Epichlorohydrin and Cyclic Anhydrides Using Single- and Two-Component Metal-Free Catalysts
European Polymer Journal ( IF 6 ) Pub Date : 2020-07-01 , DOI: 10.1016/j.eurpolymj.2020.109820
Boru Zhang , Heng Li , Huitong Luo , Junpeng Zhao

Abstract Epichlorohydrin (ECH), a chloromethyl-carrying epoxide, is subject to alcohol-initiated ring-opening copolymerization with cyclic anhydrides using a mild phosphazene base (t-BuP1) or a Lewis pair comprising t-BuP1 and triethylborane as an organic/metal-free catalyst. The products exhibit controlled molar mass and strictly alternating sequence distribution without ether linkages though ECH is added in excess. The single-component organobase catalyst favors elevated reaction temperature (60 °C) and leads to broad molar mass distribution, especially at a relatively high catalyst loading, due to the nucleophilic substitution (NS) of the ECH chloromethyl groups by the chain-end carboxylate. This side reaction suspends the propagation of some chains and generates chloride anions that can reinitiate the copolymerization, thus leads to low-molar-mass byproducts. Meanwhile, the epoxy-ended copolymers may undergo chain-end ring opening to form high-molar-mass byproducts. On the other hand, the two-component catalyst allows for a wider range of reaction temperature (25–60 °C) and higher copolymerization rate. NS can be significantly delayed at room temperature with optimized catalyst loading and composition, resulting in narrowly distributed molar mass, ranging from 2 to 30 kg mol−1, at high or complete anhydride conversion. Interestingly, NS still occurs at the end of the copolymerization so that pendent- and end-group bifunctionalized polyester can be achieved in one synthetic step.

中文翻译:

表氯醇和环酐使用单组分和双组分无金属催化剂的开环交替共聚

摘要 环氧氯丙烷 (ECH) 是一种携带氯甲基的环氧化物,使用温和的磷腈碱 (t-BuP1) 或包含 t-BuP1 和三乙基硼烷作为有机/金属的路易斯对与环酐进行醇引发的开环共聚。 - 无催化剂。尽管 ECH 过量添加,但产物表现出受控的摩尔质量和严格交替的序列分布,没有醚键。由于链端羧酸盐对 ECH 氯甲基的亲核取代 (NS),单组分有机碱催化剂有利于提高反应温度 (60 °C) 并导致摩尔质量分布较宽,尤其是在催化剂负载量相对较高的情况下. 这种副反应会暂停一些链的增长并产生氯阴离子,可以重新引发共聚反应,从而导致低摩尔质量的副产品。同时,环氧封端的共聚物可以进行链端开环以形成高摩尔质量的副产物。另一方面,双组分催化剂允许更宽的反应温度范围(25-60°C)和更高的共聚速率。NS 可以在室温下通过优化催化剂负载和组成显着延迟,导致摩尔质量分布窄,范围为 2 至 30 kg mol-1,酸酐转化率高或完全。有趣的是,NS 仍然发生在共聚结束时,因此可以在一个合成步骤中实现侧基和端基双官能化聚酯。双组分催化剂允许更宽的反应温度范围(25-60°C)和更高的共聚速率。NS 可以在室温下通过优化催化剂负载和组成显着延迟,导致摩尔质量分布窄,范围为 2 至 30 kg mol-1,酸酐转化率高或完全。有趣的是,NS 仍然发生在共聚结束时,因此可以在一个合成步骤中实现侧基和端基双官能化聚酯。双组分催化剂允许更宽的反应温度范围(25-60°C)和更高的共聚速率。NS 可以在室温下通过优化催化剂负载和组成显着延迟,导致摩尔质量分布窄,范围为 2 至 30 kg mol-1,酸酐转化率高或完全。有趣的是,NS 仍然发生在共聚结束时,因此可以在一个合成步骤中实现侧基和端基双官能化聚酯。
更新日期:2020-07-01
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