Kimura Shinya, Adachi Kurea, Ishii Yoshiki, Komiyama Tomoki, Saito Takuho, Nakayama Naofumi, Yokoya Masashi, Takaya Hikaru, Yagai Shiki, Kawai Shinnosuke, Uchihashi Takayuki, Yamanaka Masamichi
Meiji Pharmaceutical University, Kiyose, Tokyo, Japan.
Department of Physics and Institute for Glyco-core Research (iGCORE), Nagoya University, Nagoya, Japan.
Nat Commun. 2025 Apr 22;16(1):3758. doi: 10.1038/s41467-025-59032-6.
Despite being a promising soft material embodied by molecular self-assembly, the formation mechanism of supramolecular gels remains challenging to fully understand. Here we provide molecular to nanoscopic insights into the formation mechanism of gel-forming fibers from a urea derivative. High-speed atomic force microscopy of the urea derivative revealed the presence of a lag phase prior to the formation of supramolecular fibers, suggesting a nucleation process. The fiber growth kinetics differ at both termini of the fiber, indicating a directional hydrogen-bonding motif by the urea units, which is supported by single-crystal X-ray crystallography of a reference compound. Moreover, we observed an intermittent growth pattern of the fibers with repeated elongation and pause phases. This unique behavior can be simulated by a theoretical block-stacking model. A statistical analysis of the concentration-dependent lag time on macroscopic observation of the gelation suggests the presence of a tetrameric or octameric nucleus of the urea molecules.
尽管超分子凝胶是分子自组装形成的一种很有前景的软材料，但其形成机制仍极具挑战性，难以被完全理解。在此，我们从分子层面到纳米层面深入探究了一种尿素衍生物形成凝胶纤维的机制。对该尿素衍生物进行的高速原子力显微镜观察显示，在超分子纤维形成之前存在一个延迟期，这表明存在成核过程。纤维两端的生长动力学不同，这表明尿素单元存在定向氢键模式，这一观点得到了一种参考化合物的单晶X射线晶体学的支持。此外，我们观察到纤维具有间歇性生长模式，包括反复的伸长和暂停阶段。这种独特行为可以通过一个理论上的块状堆积模型来模拟。对凝胶宏观观察中浓度依赖性延迟时间的统计分析表明，存在尿素分子的四聚体或八聚体核。
