Tandem Unzipping and Scrambling Reactions for the Synthesis of Alternating Copolymers by the Cationic Ring-Opening Copolymerization of a Cyclic Acetal and a Cyclic Ester,ACS Macro Letters

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Tandem Unzipping and Scrambling Reactions for the Synthesis of Alternating Copolymers by the Cationic Ring-Opening Copolymerization of a Cyclic Acetal and a Cyclic Ester
ACS Macro Letters ( IF 5.1 ) Pub Date : 2019-12-30 , DOI: 10.1021/acsmacrolett.9b00874
Motoki Higuchi ₁ , Arihiro Kanazawa ₁ , Sadahito Aoshima ₁

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Cationic copolymerization of different types of monomers, 4-hydroxybutyl vinyl ether (HBVE) and ε-caprolactone (CL), was explored using EtSO₃H as an acid catalyst, producing copolymers with a remarkably wide variety of compositions and sequences. In the initial stage of the reaction, HBVE was unexpectedly isomerized to 2-methyl-1,3-dioxepane (MDOP), followed by concurrent copolymerization of MDOP and CL via active chain end and activated monomer mechanisms, respectively. The compositions and sequences of the copolymers were tunable, depending on the initial monomer concentrations. Moreover, a unique method was developed for transforming a copolymer with no CL homosequences into an “alternating” copolymer by removing MDOP from the system using a vacuum pump. This was achieved by the tandem reactions of depolymerization (unzipping) and random transacetalization (scrambling) under thermodynamic control. Specifically, the unzipping of HBVE homosequences proceeded at the oxonium chain end until a nondissociable ester bond emerged next to the chain end, while the scrambling of the main chain via transacetalization transferred midchain HBVE homosequences into the polymer chain end.

中文翻译：

环状缩醛和环状酯的阳离子开环共聚合成交替共聚物的串联解链加扰反应

_{使用 EtSO 3}探索了不同类型单体 4-羟丁基乙烯基醚 (HBVE) 和 ε-己内酯 (CL) 的阳离子共聚H 作为酸催化剂，产生具有非常广泛的组成和序列的共聚物。在反应的初始阶段，HBVE 出人意料地异构化为 2-甲基-1,3-二氧杂环戊烷 (MDOP)，随后 MDOP 和 CL 分别通过活性链端和活化单体机制同时共聚。取决于初始单体浓度，共聚物的组成和顺序是可调的。此外，还开发了一种独特的方法，通过使用真空泵从系统中去除 MDOP，将没有 CL 均序列的共聚物转化为“交替”共聚物。这是通过在热力学控制下的解聚（解压缩）和随机反缩醛化（加扰）的串联反应实现的。具体来说，

更新日期：2019-12-30

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