Hurst Paul Joshua, Mulvey Justin T, Bone Rebecca A, Selmani Serxho, Hudson Redford F, Guan Zhibin, Green Jason R, Patterson Joseph P
Department of Chemistry, University of California, Irvine Irvine California 92697 USA
Center for Complex and Active Materials, University of California, Irvine Irvine California 92697 USA.
Chem Sci. 2023 Dec 18;15(3):1106-1116. doi: 10.1039/d3sc05790a. eCollection 2024 Jan 17.
Inspired by the adaptability of biological materials, a variety of synthetic, chemically driven self-assembly processes have been developed that result in the transient formation of supramolecular structures. These structures form through two simultaneous reactions, forward and backward, which generate and consume a molecule that undergoes self-assembly. The dynamics of these assembly processes have been shown to differ from conventional thermodynamically stable molecular assemblies. However, the evolution of nanoscale morphologies in chemically driven self-assembly and how they compare to conventional assemblies has not been resolved. Here, we use a chemically driven redox system to separately carry out the forward and backward reactions. We analyze the forward and backward reactions both sequentially and synchronously with time-resolved cryogenic transmission electron microscopy (cryoEM). Quantitative image analysis shows that the synchronous process is more complex and heterogeneous than the sequential process. Our key finding is that a thermodynamically unstable stacked nanorod phase, briefly observed in the backward reaction, is sustained for ∼6 hours in the synchronous process. Kinetic Monte Carlo modeling show that the synchronous process is driven by multiple cycles of assembly and disassembly. The collective data suggest that chemically driven self-assembly can create sustained morphologies not seen in thermodynamically stable assemblies by kinetically stabilizing transient intermediates. This finding provides plausible design principles to develop and optimize supramolecular materials with novel properties.
受生物材料适应性的启发，人们开发了多种合成的、化学驱动的自组装过程，这些过程导致超分子结构的瞬态形成。这些结构通过两个同时进行的反应形成，即正向反应和逆向反应，这两个反应生成并消耗一种进行自组装的分子。这些组装过程的动力学已被证明与传统的热力学稳定分子组装不同。然而，化学驱动自组装中纳米级形态的演变以及它们与传统组装的比较尚未得到解决。在这里，我们使用化学驱动的氧化还原系统分别进行正向和逆向反应。我们使用时间分辨低温透射电子显微镜（cryoEM）对正向和逆向反应进行了顺序和同步分析。定量图像分析表明，同步过程比顺序过程更复杂且更不均匀。我们的关键发现是，在逆向反应中短暂观察到的热力学不稳定的堆叠纳米棒相在同步过程中持续约6小时。动力学蒙特卡罗模拟表明，同步过程由多个组装和解组装循环驱动。这些综合数据表明，化学驱动的自组装可以通过动力学稳定瞬态中间体来创造热力学稳定组装中未见的持续形态。这一发现为开发和优化具有新颖性质的超分子材料提供了合理的设计原则。
