Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093.
Materials Science and Engineering Program, University of California San Diego, La Jolla, CA 92093.
Proc Natl Acad Sci U S A. 2020 Sep 22;117(38):23385-23392. doi: 10.1073/pnas.2001861117. Epub 2020 Sep 9.
Understanding hydrogen-bond interactions in self-assembled lattice materials is crucial for preparing such materials, but the role of hydrogen bonds (H bonds) remains unclear. To gain insight into H-bond interactions at the materials' intrinsic spatial scale, we investigated ultrafast H-bond dynamics between water and biomimetic self-assembled lattice materials (composed of sodium dodecyl sulfate and β-cyclodextrin) in a spatially resolved manner. To accomplish this, we developed an infrared pump, vibrational sum-frequency generation (VSFG) probe hyperspectral microscope. With this hyperspectral imaging method, we were able to observe that the primary and secondary OH groups of β-cyclodextrin exhibit markedly different dynamics, suggesting distinct H-bond environments, despite being separated by only a few angstroms. We also observed another ultrafast dynamic reflecting a weakening and restoring of H bonds between bound water and the secondary OH of β-cyclodextrin, which exhibited spatial uniformity within self-assembled domains, but heterogeneity between domains. The restoration dynamics further suggest heterogeneous hydration among the self-assembly domains. The ultrafast nature and meso- and microscopic ordering of H-bond dynamics could contribute to the flexibility and crystallinity of the material--two critically important factors for crystalline lattice self-assemblies--shedding light on engineering intermolecular interactions for self-assembled lattice materials.
理解自组装晶格材料中的氢键相互作用对于制备这种材料至关重要，但氢键（H 键）的作用仍不清楚。为了深入了解材料内在空间尺度上的氢键相互作用，我们以空间分辨的方式研究了水和仿生自组装晶格材料（由十二烷基硫酸钠和β-环糊精组成）之间超快氢键动力学。为了实现这一目标，我们开发了一种红外泵浦、振动和频产生（VSFG）探针高光谱显微镜。通过这种高光谱成像方法，我们观察到β-环糊精的主要和次要 OH 基团表现出明显不同的动力学，尽管它们仅相隔几个埃，但暗示了不同的氢键环境。我们还观察到另一种超快动力学，反映了结合水和β-环糊精的二级 OH 之间氢键的减弱和恢复，这种动力学在自组装域内表现出空间均匀性，但在域之间表现出异质性。恢复动力学进一步表明自组装域之间存在异质水合作用。氢键动力学的超快性质以及介观和微观有序性可能有助于材料的柔韧性和结晶度——这是结晶晶格自组装的两个极其重要的因素——为自组装晶格材料的分子间相互作用工程提供了启示。
