Department of Chemistry , Indiana University , 800 East Kirkwood Avenue , Bloomington , Indiana 47405 , United States.
School of Polymer Science and Engineering , The University of Southern Mississippi , 118 College Drive , Hattiesburg , Mississippi 39406 , United States.
J Am Chem Soc. 2019 Mar 27;141(12):4980-4989. doi: 10.1021/jacs.9b00248. Epub 2019 Mar 6.
Supramolecular polymers have enabled far-reaching fundamental science and the development of diverse macromolecular technologies owing to the reversible and noncovalent chemical connectivities that define their properties. Despite the unabated development of these materials using highly tailorable recognition elements, anion-based polymers remain rare as a result of the weak interactions they mediate. Here, we use design rules inspired by cation-driven polymers to demonstrate a new noncovalent link based on receptor-stabilized anion-anion interactions that enables the efficient linear polymerization of simple difunctional phosphonates. The linear main chain connectivity and molecular topology were confirmed by single crystal X-ray diffraction, which demonstrates the rare 2:2 stoichiometry between the anionic phosphonate end groups and a pair of π-stacked cyanostar macrocycles. The stability of these links enables rapid polymerization of difunctional phosphonates employing different aliphatic linkers (CH, CH, CH, CH). Diphosphonates with greater chain flexibility (CH) enable greater polymerization with an average degree of polymerization of nine emerging at 10 mM. Viscosity measurements show a transition from oligomers to polymers at the critical polymerization concentration of 5 mM. In a rare correlation, NMR spectroscopy shows a coincident molecular signature of the polymerization at 5 mM. These polymers are highly concentration dependent, reversibly polymerize with acid and base, and respond to competitive anions. They display the design simplicity of metallo-supramolecular polymers with transfer of the strong 2:2 recognition chemistry to macromolecules. The simplicity and understanding of this new class of supramolecular polymer is anticipated to open opportunities in tailoring anion-based functional materials.
超分子聚合物由于其具有可逆和非共价的化学连接性，从而定义了其性质，因此实现了深远的基础科学和各种高分子技术的发展。尽管这些材料使用高度可定制的识别元件不断得到发展，但由于它们介导的弱相互作用，基于阴离子的聚合物仍然很少。在这里，我们使用受阳离子驱动聚合物启发的设计规则，展示了一种新的非共价键，该键基于受体稳定的阴离子-阴离子相互作用，能够有效地线性聚合简单的双官能膦酸酯。单晶 X 射线衍射证实了线性主链连接性和分子拓扑结构，这证明了阴离子膦酸酯端基与一对π堆叠氰星大环之间存在罕见的 2:2 化学计量比。这些键的稳定性能够快速聚合具有不同脂肪族连接基（CH、CH、CH、CH）的双官能膦酸酯。具有更大链柔性（CH）的二膦酸酯能够实现更大程度的聚合，在 10 mM 时出现平均聚合度为九的情况。粘度测量表明，在 5 mM 的临界聚合浓度下，从低聚物到聚合物的转变。在罕见的相关性中，NMR 光谱显示出在 5 mM 时聚合的分子特征一致。这些聚合物高度依赖于浓度，可与酸和碱可逆聚合，并对竞争性阴离子作出响应。它们具有金属超分子聚合物的设计简单性，将强 2:2 识别化学转移到了大分子中。这种新型超分子聚合物的简单性和可理解性预计将为定制基于阴离子的功能材料开辟机会。
