Department of Inorganic and Organic Chemistry, Universitat Jaume I, 12071 Castelló de la Plana, Spain.
Department of Inorganic and Organic Chemistry, Universitat Jaume I, 12071 Castelló de la Plana, Spain.
J Colloid Interface Sci. 2023 Apr;635:524-534. doi: 10.1016/j.jcis.2022.12.134. Epub 2022 Dec 28.
Understanding the factors that control the formation of (supra)molecular hydrogels permits a rational tuning of their properties and represents a primary challenge for developing smart biocompatible soft materials. Hydrogel formation by molecular amphiphilic anions at millimolar concentrations is counterintuitive, considering the solubility of these species in water. Here we report hydrogel formation by a simple anionic molecular amphiphile and a rationale for the fibrillisation process observed. The studied molecule, DodValSuc, consists of a 12C alkyl chain, an l-valine unit and a terminal succinic acid moiety. Hydrogelation depends to a large degree on the nature and concentration of the alkaline cations present in the medium (Li, Na or K). As a result, gelation efficiency and properties like thermal stability or rheology are highly tunable using the alkaline cation present or its concentration as variables. A detailed study is reported, which includes the determination of minimum gelation concentration (MGC) by tabletop rheology, critical micelle concentration (CMC) using pyrene as a fluorescent probe, thermal stability (solubility) by H NMR, the morphology of the fibres by transmission electron microscopy (TEM), crystallinity by X-ray diffraction (XRD) and gel strength by oscillatory rheology. Additionally, dynamic light scattering (DLS) was used to evaluate the size of the micelles and permitted monitoring of the fibrillisation process. Altogether, the results are consistent with the formation of micelles that experience head crystallisation and subsequent aggregation into crystalline fibres. The alkaline cations play a crucial role in providing the cement that glues together the gelator molecules, making their concentration a critical parameter for gelation efficiency and properties. Furthermore, the gelation-promoting effects are inversely correlated with the size of the cations so that the highest thermal stability and rheological strength were found for the hydrogels formed in the presence of Li
了解控制（超）分子水凝胶形成的因素可以使它们的性质得到合理的调节，这是开发智能生物相容性软材料的主要挑战。考虑到这些物质在水中的溶解度，在毫摩尔浓度下，分子两亲性阴离子形成水凝胶是违反直觉的。在这里，我们报告了一种简单的阴离子分子两亲物的水凝胶形成，并对观察到的纤维形成过程提出了合理的解释。所研究的分子 DodValSuc 由 12C 烷基链、l-缬氨酸单元和末端琥珀酸部分组成。水凝胶化在很大程度上取决于存在于介质中的碱性阳离子（Li、Na 或 K）的性质和浓度。因此，凝胶效率和热稳定性或流变学等性质可以通过使用存在的碱性阳离子或其浓度作为变量来高度调节。报告了详细的研究，其中包括通过台式流变学确定最小凝胶浓度（MGC）、使用芘作为荧光探针确定临界胶束浓度（CMC）、通过 H NMR 确定热稳定性（溶解度）、通过透射电子显微镜（TEM）确定纤维形态、通过 X 射线衍射（XRD）确定结晶度和通过振荡流变学确定凝胶强度。此外，还使用动态光散射（DLS）评估胶束的大小，并监测纤维形成过程。总之，结果与胶束的形成一致，这些胶束经历头部结晶化，然后聚集形成结晶纤维。碱性阳离子在提供将凝胶剂分子粘在一起的水泥方面起着至关重要的作用，因此其浓度是凝胶化效率和性质的关键参数。此外，凝胶促进作用与阳离子的大小成反比，因此在存在 Li 的情况下形成的水凝胶具有最高的热稳定性和流变学强度。
