Advanced Soft Matter group, Department of Chemical Engineering, Delft University of Technology , van der Maasweg 9, 2629 HZ Delft, The Netherlands.
Acc Chem Res. 2016 Jul 19;49(7):1440-7. doi: 10.1021/acs.accounts.6b00137. Epub 2016 Jun 17.
One often thinks of catalysts as chemical tools to accelerate a reaction or to have a reaction run under more benign conditions. As such, catalysis has a role to play in the chemical industry and in lab scale synthesis that is not to be underestimated. Still, the role of catalysis in living systems (cells, organisms) is much more extensive, ranging from the formation and breakdown of small molecules and biopolymers to controlling signal transduction cascades and feedback processes, motility, and mechanical action. Such phenomena are only recently starting to receive attention in synthetic materials and chemical systems. "Smart" soft materials could find many important applications ranging from personalized therapeutics to soft robotics to name but a few. Until recently, approaches to control the properties of such materials were largely dominated by thermodynamics, for instance, looking at phase behavior and interaction strength. However, kinetics plays a large role in determining the behavior of such soft materials, for instance, in the formation of kinetically trapped (metastable) states or the dynamics of component exchange. As catalysts can change the rate of a chemical reaction, catalysis could be used to control the formation, dynamics, and fate of supramolecular structures when the molecules making up these structures contain chemical bonds whose formation or exchange are susceptible to catalysis. In this Account, we describe our efforts to use synthetic catalysts to control the properties of supramolecular hydrogels. Building on the concept of synthesizing the assembling molecule in the self-assembly medium from nonassembling precursors, we will introduce the use of catalysis to change the kinetics of assembler formation and thereby the properties of the resulting material. In particular, we will focus on the synthesis of supramolecular hydrogels where the use of a catalyst provides access to gel materials with vastly different appearance and mechanical properties or controls localized gel formation and the growth of gel objects. As such, catalysis will be applied to create molecular materials that exist outside of chemical equilibrium. In all, using catalysts to control the properties of soft materials constitutes a new avenue for catalysis far beyond the traditional use in industrial and lab scale synthesis.
人们通常认为催化剂是一种化学工具，可以加速反应或在更温和的条件下进行反应。因此，催化在化学工业和实验室规模合成中发挥着不可低估的作用。尽管如此，催化在生命系统（细胞、生物体）中的作用要广泛得多，范围从小分子和生物聚合物的形成和分解到控制信号转导级联和反馈过程、运动和机械作用。这些现象最近才开始在合成材料和化学系统中受到关注。“智能”软材料可以在许多重要领域找到应用，从个性化治疗到软机器人等等。直到最近，控制这些材料性能的方法在很大程度上还受到热力学的控制，例如，研究相行为和相互作用强度。然而，动力学在决定软材料的行为方面起着重要作用，例如，在形成动力学捕获（亚稳态）状态或组分交换的动力学方面。由于催化剂可以改变化学反应的速率，因此可以使用催化来控制超分子结构的形成、动力学和命运，当构成这些结构的分子包含的化学键的形成或交换容易受到催化时。在本述评中，我们描述了使用合成催化剂来控制超分子水凝胶性质的努力。基于在自组装介质中从非组装前体制备组装分子的概念，我们将介绍使用催化来改变组装体形成的动力学，从而改变所得材料的性质。特别是，我们将重点介绍超分子水凝胶的合成，其中催化剂的使用可以获得外观和机械性能截然不同的凝胶材料，或控制局部凝胶形成和凝胶物体的生长。因此，催化将用于创造存在于化学平衡之外的分子材料。总之，使用催化剂来控制软材料的性质为催化开辟了一条新途径，远远超出了在工业和实验室规模合成中的传统应用。
