Insights into the Effects of 2:1 鈥淪andwich-Type鈥?Crown-Ether/Metal-Ion Complexes in Responsive Host鈥揋uest Systems

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• 作者：Hai-Rong Yu ; Jia-Qi Hu ; Xiao-Hua Lu ; Xiao-Jie Ju ; Zhuang Liu ; Rui Xie ; Wei Wang ; Liang-Yin Chu
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：January 29, 2015
• 年：2015
• 卷：119
• 期：4
• 页码：1696-1705
• 全文大小：567K
• ISSN：1520-5207

文摘

In-depth investigations of the specific ion-responsive characteristics based on 2:1 鈥渟andwich鈥?structures and effects of crown ether cavity sizes on the metal-ion/crown-ether complexation are systematically performed with a series of PNIPAM-based responsive copolymers containing similar contents of crown ether units with different cavity dimensions (12-crown-4 (12C4), 15-crown-5 (15C5), 18-crown-6 (18C6)). The lower critical solution temperature (LCST) values of copolymers in deionized water shift to lower temperatures gradually when the crown ether contents increase or the ring sizes decrease from 18C6 to 12C4. With increasing the concentrations of alkali metal ions (Na⁺, K⁺, Cs⁺) or the contents of pendent crown ether groups, the copolymers with different crown ether cavity sizes exhibit higher selectivity and sensitivity to corresponding cations. Importantly, the ion sensitivities of the copolymers in response to corresponding alkali metal ions increase dramatically with an increase in the crown ether cavity size. Interestingly, a linear relationship between the crown ether cavity size and the diameter of corresponding cation for the formation of stable 2:1 鈥渟andwich鈥?complexes is found for the first time, from which the size of metal ions or other guests that able to form 2:1 鈥渟andwich鈥?complexes with crown ethers can be deduced. The results in this work are valuable and useful for further developments and practical applications of various crown-ether-based smart materials.