Light- and Heat-Triggered Reversible Linear-Cyclic Topological Conversion of Telechelic Polymers with Anthryl End Groups.
Light- and Heat-Triggered Reversible Linear-Cyclic Topological Conversion of Telechelic Polymers with Anthryl End Groups.
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DOI：
10.1021/jacs.6b00800
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发表时间：
2016-03
影响因子：
15
通讯作者：
Takuya Yamamoto;Sakyo Yagyu;Y. Tezuka
中科院分区：
文献类型：
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作者：
Takuya Yamamoto;Sakyo Yagyu;Y. Tezuka
本研究对不同分子量的亲水性和疏水性聚合物的可逆线性-环状拓扑转化进行了全面的研究。该反应由光或热引发，其可逆地二聚化并裂解遥爪的蒽基或香豆素基端基。合成了以蒽基为端基，通过给电子（Ant-O-PEO和Ant-CH 2-PEO）和吸电子（Ant-CO2-PEO）连接的聚环氧乙烷遥爪。虽然Ant-O-PEO和Ant-CH 2-PEO在365 nm的光照射下分解，但通过NMR、SEC和MALDI-TOF MS显示，Ant-CO2-PEO通过蒽基端基在水和有机溶剂中的光二聚反应有效地环化。分子量越低，环化进行得越快。当环化的Ant-CO2-PEO在150 °C下整体加热时，聚合物定量地转化回原始的线性拓扑结构。此外，可重复的线性环状拓扑转换被证实。具有蒽基端基的疏水性聚（四氢呋喃）遥爪（Ant-PTHF）的可逆拓扑转化也是成功的。此外，聚（环氧乙烷）遥爪与香豆素端基（Cou-PEO）也环化的照射在365 nm的水。然而，当在甲醇中进行时，环化几乎不发生，这可能是由于香豆素基端基缺乏足够的疏水相互作用。在254 nm下照射环化的Cou-PEO以测试线性化，发现线性产物和环状前体可能是光平衡的。
This study demonstrates the comprehensive investigation on the reversible linear-cyclic topological conversion of hydrophilic and hydrophobic polymers with various molecular weights. The reactions were triggered by light or heat, which reversibly dimerize and cleave the anthryl or coumarinyl end groups of the telechelics. Poly(ethylene oxide) telechelics with anthryl end groups attached through electron-donating (Ant-O-PEO and Ant-CH2-PEO) and electron-withdrawing (Ant-CO2-PEO) linking groups were synthesized. While Ant-O-PEO and Ant-CH2-PEO decomposed upon photoirradiation at 365 nm, Ant-CO2-PEO efficiently cyclized through the photodimerization of the anthryl end groups both in water and in organic solvents shown by NMR, SEC, and MALDI-TOF MS. The lower the molecular weight, the faster the cyclization proceeded. When cyclized Ant-CO2-PEO was heated at 150 °C in bulk, the polymers quantitatively converted back into the original linear topology. Furthermore, repeatable linear-cyclic topological conversion was confirmed. The reversible topological conversion of hydrophobic poly(tetrahydrofuran) telechelics with anthryl end groups (Ant-PTHF) was also successful. In addition, poly(ethylene oxide) telechelics with coumarinyl end groups (Cou-PEO) were also cyclized by irradiation at 365 nm in water. However, the cyclization hardly occurred when performed in methanol likely due to the lack of sufficient hydrophobic interaction of the coumarinyl end groups. Cyclized Cou-PEO was irradiated at 254 nm to test for linearization, finding the linear product and cyclic precursor were likely photoequilibrated.