Low-molecular-weight gelators: Elucidating the principles of gelation based on gelator solubility and a cooperative self-assembly model
Low-molecular-weight gelators: Elucidating the principles of gelation based on gelator solubility and a cooperative self-assembly model
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DOI：
10.1021/ja801804c
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发表时间：
2008-07-16
影响因子：
15
通讯作者：
Smith, David K.
中科院分区：
文献类型：
--
作者：
Hirst, Andrew R.;Coates, Ian A.;Smith, David K.
本文强调了溶解度在影响凝胶化中所起的关键作用，并证明了凝胶化过程的许多方面取决于这个重要参数。特别是，我们涉及的热稳定性（T-凝胶）和最小凝胶化浓度（MGC）的小分子凝胶化的溶解度和合作的自组装凝胶剂积木的值。通过采用由简单NMR测量确定的溶解度数据的van 't霍夫分析，我们能够生成反映网络化胶凝因子完全溶解的计算温度的T-calc值。T-calc的浓度依赖性允许先前难以合理化的“平台区域”热稳定性值在胶凝剂分子设计方面得以阐明。这是证明了一个家庭的四个胶凝剂与赖氨酸单元连接到每个脂肪族二胺的末端，与不同的外围基团（Z或蜜蜂）在不同的位置上的外围的分子。通过调节胶凝剂的外围保护基团，改变了系统的溶解度，这又控制了系统的饱和点，从而控制了网络形成发生时的浓度。我们报告说，凝胶剂的临界浓度（C-crit）纳入凝胶内的固相样品跨越网络是不变的凝胶剂结构设计。然而，由于一些系统具有较高的溶解度，它们是不太有效的胶凝剂，并且需要应用较高的总浓度来实现胶凝，因此揭示了MGC参数在胶凝中的作用。此外，胶凝因子结构设计还通过溶解度效应调节协同自组装的水平，如通过将协同结合模型应用于NMR数据所确定的。最后，通过对天然凝胶的小角中子和X射线散射（SANS/SAXS）研究了凝胶因子化学设计对网络化凝胶因子空间结构的影响，并提出了一个初步的自组装模型.
This paper highlights the key role played by solubility in influencing gelation and demonstrates that many facets of the gelation process depend on this vital parameter. In particular, we relate thermal stability (T-gel) and minimum gelation concentration (MGC) values of small-molecule gelation in terms of the solubility and cooperative self-assembly of gelator building blocks. By employing a van't Hoff analysis of solubility data, determined from simple NMR measurements, we are able to generate T-calc values that reflect the calculated temperature for complete solubilization of the networked gelator. The concentration dependence of T-calc allows the previously difficult to rationalize "plateau-region" thermal stability values to be elucidated in terms of gelator molecular design. This is demonstrated for a family of four gelators with lysine units attached to each end of an aliphatic diamine, with different peripheral groups (Z or Bee) in different locations on the periphery of the molecule. By tuning the peripheral protecting groups of the gelators, the solubility of the system is modified, which in turn controls the saturation point of the system and hence controls the concentration at which network formation takes place. We report that the critical concentration (C-crit) of gelator incorporated into the solid-phase sample-spanning network within the gel is invariant of gelator structural design. However, because some systems have higher solubilities, they are less effective gelators and require the application of higher total concentrations to achieve gelation, hence shedding light on the role of the MGC parameter in gelation. Furthermore, gelator structural design also modulates the level of cooperative self-assembly through solubility effects, as determined by applying a cooperative binding model to NMR data. Finally, the effect of gelator chemical design on the spatial organization of the networked gelator was probed by small-angle neutron and X-ray scattering (SANS/SAXS) on the native gel, and a tentative self-assembly model was proposed.