Highly Controllable Ring鈥揅hain Equilibrium in Quadruply Hydrogen Bonded Supramolecular Polymers

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• 作者：Tangxin Xiao ; Xiaoqing Feng ; Shuyang Ye ; Yangfan Guan ; Shao-Lu Li ; Qi Wang ; Ya Ji ; Dunru Zhu ; Xiaoyu Hu ; Chen Lin ; Yi Pan ; Leyong Wang
• 刊名：Macromolecules
• 出版年：2012
• 出版时间：December 21, 2012
• 年：2012
• 卷：45
• 期：24
• 页码：9585-9594
• 全文大小：491K
• 年卷期：v.45,no.24(December 21, 2012)
• ISSN：1520-5835

文摘

Electron-rich dioxynaphthalene (DNP) group bridged bifunctional ureidopyrimidinone (UPy) derivatives (L1, L2, and L3) were synthesized, which could form small cyclic monomers, oligomers, or linear supramolecular polymers at certain concentration in solution, to achieve a highly controllable ring鈥揷hain equilibrium self-assembling supramolecular system. The ring鈥揷hain equilibrium of these supramolecular monomers constructed by different lengths of oligo(ethylene oxide) (oligoEO) chain as spacers were investigated by a combination of techniques, such as ¹H NMR, DOSY, single-crystal X-ray diffraction, and viscometry. The experiment results demonstrated that there exists intramolecular 蟺鈥撓€ stacking interaction between DNP group and intramolecularly dimerized UPy motif in the monomeric cyclic form of these supramolecular monomers, and the strength of this 蟺鈥撓€ stacking interaction directly depends on the length of the oligoEO chain. Furthermore, strong intramolecular 蟺鈥撓€ stacking interaction was found to promote self-assembly favorable for intramolecularly cyclic monomerization, leading to a great increase of critical polymerization concentration (CPC). Monomer L1a with the shortest length of oligoEO chain is present as an exclusive type of intramolecularly hydrogen-bonded assembly, namely the cyclic monomers, over a broad concentration range (1.6鈥?00 mM) in solution. Single crystal structure of the cyclic monomer L1b, which is an analogue of L1a, was thoroughly studied. The CPC values of monomer L2 and L3 with longer oligoEO chain are ca. 70 and 23 mM, respectively. However, L2 and L3 could perform selective cyclization over the entire concentration range in solution after threading into the tetracationic cyclobis(paraquat-p-phenylene)cyclophane (CBPQT⁴⁺) driven by host鈥揼uest interaction, which provides another supramolecular strategy to control ring鈥揷hain equilibrium. The combined results may provide new insights into the ring鈥揷hain equilibrium and offer valuable information on the understanding of the correlation between supramolecular assistance and polymerizability.