Alternating Cationic Copolymerization of Vinyl Ethers and Aryl-Substituted Cyclic Acetals: Structural Investigation of Effects of Cyclic Acetals on Copolymerizability
Alternating Cationic Copolymerization of Vinyl Ethers and Aryl-Substituted Cyclic Acetals: Structural Investigation of Effects of Cyclic Acetals on Copolymerizability
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DOI：
10.1021/acs.macromol.2c00354
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发表时间：
2022-05
期刊：
影响因子：
5.5
通讯作者：
K. Maruyama;Arihiro Kanazawa;S. Aoshima
中科院分区：
文献类型：
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作者：
K. Maruyama;Arihiro Kanazawa;S. Aoshima
通过同时进行乙烯基加成和开环反应，研究了环缩醛结构差异对乙烯基类单体阳离子共聚反应的影响。在合适的反应条件下，用2-氯乙基乙烯基醚(CEVE)成功地合成了一系列烷基和芳基取代的环缩醛。特别是，芳基取代的2-(4-甲氧基苯基)-1，3-二氧杂环戊烷(PMPDOL)与CEVE的共聚涉及PMPDOL和CEVE之间的排他性交叉反应，导致交替共聚。PMPDOL与其他乙烯基醚和苯乙烯衍生物的共聚也通过频繁的交叉反应进行，而PMPDOL的甲基取代物2-甲基-1，3-二氧杂环戊烷与除CEVE外的乙烯基单体的共聚反应可以忽略不计。环缩醛取代基的不同显著影响了传播反应中生成的碳正离子周围的电子和空间环境，这与交叉反应的频率有关。交替共聚物的酸解由于在主链上周期性地结合缩醛结构而导致单一化合物的完全降解和选择性生成，这支持了共聚物的良好结构。单体竞聚率也与芳基和烷基取代的环缩醛的共聚性差异相一致。根据扩散反应的反应机理，讨论了环缩醛在共聚反应中的结构-聚合性关系。
The effects of the structural difference of cyclic acetals were investigated in the cationic copolymerization with vinyl monomers via the concurrent vinyl-addition and ring-opening mechanisms. A series of alkyl- and aryl-substituted cyclic acetals were successfully copolymerized with 2-chloroethyl vinyl ether (CEVE) under appropriate conditions. In particular, copolymerization of an aryl-substituted 2-(4-methoxyphenyl)-1,3-dioxolane (PMPDOL) with CEVE involved exclusive crossover reactions between PMPDOL and CEVE, resulting in alternating copolymers. Copolymerization of PMPDOL and other vinyl ethers and styrene derivatives also proceeded via the frequent crossover reactions, while the copolymerization of 2-methyl-1,3-dioxolane, a methyl-substituted counterpart of PMPDOL, with vinyl monomers except for CEVE proceeded negligibly. The difference in the substituents of cyclic acetals significantly affected the electronic and steric environments around the carbocation generated in the propagation reaction, which is related to the frequency of the crossover reaction. Acid hydrolysis of alternating copolymers resulted in complete degradation and selective generation of a single compound due to the periodic incorporation of acetal structures in the main chains, which supported the well-defined structure of copolymers. The monomer reactivity ratios were also consistent with the copolymerizability difference between the aryl- and alkyl-substituted cyclic acetals. The structure–polymerizability relationship of cyclic acetals in the copolymerization was discussed based on the reaction mechanism during the propagating reaction.