Impact of Alkyl Spacer Length on Aggregation Pathways in Kinetically Controlled Supramolecular Polymerization
Impact of Alkyl Spacer Length on Aggregation Pathways in Kinetically Controlled Supramolecular Polymerization
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DOI：
10.1021/jacs.5b11674
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发表时间：
2016-01-20
影响因子：
15
通讯作者：
Wuerthner, Frank
中科院分区：
文献类型：
--
作者：
Ogi, Soichiro;Stepanenko, Vladimir;Wuerthner, Frank
我们已经研究了一系列酰胺官能化的苝酰亚胺（PBI）有机凝胶剂分子的动力学和热力学超分子聚合，这些分子在酰胺和PBI酰亚胺基团之间具有不同长度的烷基间隔基（乙烯至戊烯链，PBI-1-C2至PBI-1-C5）。这些酰胺官能化的PBIs在低极性溶剂中形成一维纤维状纳米结构，作为化学上有利的状态。然而，我们的深入研究表明，它们的超分子聚合的动力学行为取决于间隔基的长度。丙烯和戊烯系留的PBI遵循与先前对于乙烯系留的PBI观察到的类似的聚合过程。因此，这些PBIs的单体通过酰胺和酰亚胺基团之间的分子内氢键被动力学捕获在构象受限状态。与此相反，分子内氢键键合的单体的丁烯栓系的PBI自发地自组装成纳米粒子，这构成了一个关闭路径的聚集态相对于所获得的热稳定的纤维状超分子聚合物。因此，对于这类p-共轭体系，通过在酰胺和酰亚胺基团之间引入最佳长度（C4链）的烷基连接基，可以首次实现具有高动力学稳定性的前所未有的非途径聚集体。我们目前的系统与两个竞争的成核聚集途径的能量景观是适用于超分子聚合的种子的方法的动力学控制。
We have investigated the kinetic and thermodynamic supramolecular polymerizations of a series of amide-functionalized perylene bisimide (PBI) organogelator molecules bearing alkyl spacers of varied lengths (ethylene to pentylene chains, PBI-1-C2 to PBI-1-C5) between the amide and PBI imide groups. These amide-functionalized PBIs form one-dimensional fibrous nanostructures as the thermodynamically favored states in solvents of low polarity. Our in-depth studies revealed, however, that the kinetic behavior of their supramolecular polymerization is dependent on the spacer length. Propylene- and pentylene-tethered PBIs follow a similar polymerization process as previously observed for the ethylene-tethered PBI. Thus, the monomers of these PBIs are kinetically trapped in conformationally restricted states through intramolecular hydrogen bonding between the amide and imide groups. In contrast, the intramolecularly hydrogen-bonded monomers of butylene-tethered PBI spontaneously self-assemble into nanoparticles, which constitute an off-pathway aggregate state with regard to the thermodynamically stable fibrous supramolecular polymers obtained. Thus, for this class of p-conjugated system, an unprecedented off-pathway aggregate with high kinetic stability could be realized for the first time by introducing an alkyl linker of optimum length (C4 chain) between the amide and imide groups. Our current system with an energy landscape of two competing nucleated aggregation pathways is applicable to the kinetic control over the supramolecular polymerization by the seeding approach.