Degradable Silyl Ether Polymers Synthesized by Sequence-Controlled Cationic Terpolymerization of 1,3-Dioxa-2-silacycloalkanes with Vinyl Ethers and Aldehydes
Degradable Silyl Ether Polymers Synthesized by Sequence-Controlled Cationic Terpolymerization of 1,3-Dioxa-2-silacycloalkanes with Vinyl Ethers and Aldehydes
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DOI：
10.1021/acs.macromol.2c00857
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发表时间：
2022-06
期刊：
影响因子：
5.5
通讯作者：
Ryosuke Hada;Arihiro Kanazawa;S. Aoshima
中科院分区：
文献类型：
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作者：
Ryosuke Hada;Arihiro Kanazawa;S. Aoshima
具有硅醚结构的聚合物由于具有硅-氧键的性质以及酸、碱和氟离子引发的降解性而受到广泛关注。在B（C6 F5）3催化下，1，3-二氧杂-2-硅杂环烷烃与乙烯基醚和醛进行阳离子三元共聚，合成了硅醚聚合物。重要的是，所有三种单体都是通过频繁的交叉反应进行有效三元聚合所不可或缺的。例如，由六元1，3-二氧杂-2-硅杂环烷烃、2-氯乙基乙烯基醚和新戊醛得到Mn为29 × 103的可降解聚合物，其上级优于产生Mn为3.3 × 103的产物的甲硅烷基单体均聚和不存在甲硅烷基单体、乙烯基醚或醛的低效共聚。此外，由于频繁和选择性的交叉反应，三元共聚物可能具有ABC型伪周期序列。所得三元共聚物在主链中具有缩醛和甲硅烷基醚部分，因此表现出酸、碱或氟离子触发的降解性。在酸性条件下，锰含量为29 × 103的柠檬酸可顺利降解为锰含量为0.3 × 103的产物。三元共聚反应的关键是醛与甲硅烷基单体衍生的氧鎓离子反应以产生可与乙烯基醚反应的碳阳离子，因为乙烯基醚不与甲硅烷基单体衍生的氧鎓离子反应。
Polymers with silyl ether moieties have been gaining considerable interest due to both the properties derived from silicon–oxygen linkages and the acid-, base-, and fluoride ion-triggered degradability. In this study, 1,3-dioxa-2-silacycloalkanes were demonstrated to function as promising monomers for the synthesis of silyl ether polymers when combined with vinyl ethers and aldehydes in cationic terpolymerization with B(C6F5)3as a catalyst. Importantly, all three monomers were indispensable for efficient terpolymerization via frequent crossover reactions. For example, a degradable terpolymer with anMnof 29 × 103was obtained from a six-membered 1,3-dioxa-2-silacycloalkane, 2-chloroethyl vinyl ether, and pivalaldehyde, which was superior to both the silyl monomer homopolymerization yielding a product with anMnof 3.3 × 103and the inefficient copolymerizations in the absence of the silyl monomer, vinyl ether, or aldehyde. Moreover, the terpolymers likely had ABC-type, pseudo-periodic sequences as a result of frequent and selective crossover reactions. The resulting terpolymers have acetal and silyl ether moieties in the main chain, thus exhibiting acid-, base-, or fluoride ion-triggered degradability. Indeed, the terpolymer with anMnof 29 × 103was smoothly degraded into a product with anMnof 0.3 × 103under acidic conditions. The key to the terpolymerization reaction was the reaction of an aldehyde with the silyl monomer-derived oxonium ion to generate a carbocation that can react with a vinyl ether because a vinyl ether does not react with the silyl monomer-derived oxonium ion.